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This PDF file contains the front matter associated with SPIE Proceedings Volume 8429, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.
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Classical spherical gradient index (GRIN) lenses (such as Maxwell Fish Eye lens, Eaton lens, Luneburg lens, etc.)
design procedure using the Abel integral equation is reviewed and reorganized. Each lens is fully defined by a function
called the angle of flight which describes the ray deflection through the lens. The radial refractive index distribution is
obtained by applying a linear integral transformation to the angle of flight. The interest of this formulation is in the
linearity of the integral transformation which allows us to derive new solutions from linear combinations of known
lenses. Beside the review of the classical GRIN designs, we present a numerical method for GRIN lenses defined by the
Abel integral equation with fixed limits, which is an ill-posed problem.
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Expanding demands on manufacturing technology increase the requirements on necessary non-contact metrology.
Several optical metrology systems are based on separated imaging (e.g. camera unit) and image generating units
(e.g. projection unit). This fact limits the geometrical miniaturization of the system. We present a compact,
highly integrated 3-D metrology system based on the fringe projection principle using a bi-directional OLED
microdisplay. The microdisplay combines light emitting pixels based on OLED technology (projection unit)
and light detecting pixels based on photo diode technology (camera unit) on one single device, realized by the
OLED-on-CMOS-technology. This technology provides the opportunity for a further miniaturization of optical
metrology systems. The 3-D metrology system is based on fringe projection onto the surface of the measurement
object. The fringes will appear deformed when observed from a dierent angle (triangulation angle). From the
deformation of the fringes the 3-D coordinates of all visible points can be calculated and thus the object shape
can be determined. For the application of an 3-D Sensor and due an internal display eect, separate lenses
for projection and imaging are necessary. The system principle and several optical system congurations are
discussed. Due to the application of the bi-directional OLED microdisplay the fringe generating elements and
the detectors will be combined into one single device. Based on this integrated device an ultra-compact and solid
system concept for 3-D surface metrology is practicable.
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PURPOSE: To present a commercially available optical modeling software tool to assist the development of optical
instrumentation and systems that utilize and/or integrate with the human eye. METHODS: A commercially available
flexible eye modeling system is presented, the Advanced Human Eye Model (AHEM). AHEM is a module that the
engineer can use to perform rapid development and test scenarios on systems that integrate with the eye. Methods
include merging modeled systems initially developed outside of AHEM and performing a series of wizard-type
operations that relieve the user from requiring an optometric or ophthalmic background to produce a complete eye
inclusive system. Scenarios consist of retinal imaging of targets and sources through integrated systems. Uses include,
but are not limited to, optimization, telescopes, microscopes, spectacles, contact and intraocular lenses, ocular
aberrations, cataract simulation and scattering, and twin eye model (binocular) systems. RESULTS: Metrics, graphical
data, and exportable CAD geometry are generated from the various modeling scenarios.
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Progressive miniaturization and mass market orientation denote a challenge to the design of dynamic optical systems
such as zoom-lenses. Two working principles can be identified: mechanical actuation and application of active optical
components. Mechanical actuation changes the focal length of a zoom-lens system by varying the axial positions of
optical elements. These systems are limited in speed and often require complex coupled movements. However, well
established optical design approaches can be applied. In contrast, active optical components change their optical
properties by varying their physical structure by means of applying external electric signals. An example are liquidlenses
which vary their curvatures to change the refractive power. Zoom-lenses benefit from active optical components
in two ways: first, no moveable structures are required and second, fast response characteristics can be realized. The precommercial
development of zoom-lenses demands simplified and cost-effective system designs. However the number of
efficient optical designs for electro-optically actuated zoom-lenses is limited. In this paper, the systematic development
of an electro-optically actuated zoom-lens will be discussed. The application of aberration polynomials enables a better
comprehension of the primary monochromatic aberrations at the lens elements during a change in magnification. This
enables an enhanced synthesis of the system behavior and leads to a simplified zoom-lens design with no moving
elements. The change of focal length is achieved only by varying curvatures of targeted integrated electro-optically
actuated lenses.
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In this paper an expression is derived to determine influence functions for optical imaging systems. The influence function
describes the wavefront change, caused by a deviation of an optical surface from its nominal shape due to any arbitrary
reason. The method is derived with the help of the paraxial approximation, using the optical design prescription from
software such as Code V or Zemax. The presented method can be used for diffraction limited projection systems. It helps
with modelling wave front aberrations caused by desired and undesired deviations of the optical surface from its nominal
shape. So it can be used for modelling mirror vibrations, thermal aberrations, the influence of manufacturing errors or
Adaptive Optical systems without using optical ray-tracing programs.
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In this work, a new two-dimensional analytic optics design method is presented that enables the coupling of
three ray sets with two lens profiles. This method is particularly promising for optical systems designed for wide
field of view and with clearly separated optical surfaces. However, this coupling can only be achieved if different
ray sets will use different portions of the second lens profile.
Based on a very basic example of a single thick lens, the Simultaneous Multiple Surfaces design method in two
dimensions (SMS2D) will help to provide a better understanding of the practical implications on the design
process by an increased lens thickness and a wider field of view. Fermat's principle is used to deduce a set of
functional differential equations fully describing the entire optical system. The transformation of these functional
differential equations into an algebraic linear system of equations allows the successive calculation of the Taylor
series coefficients up to an arbitrary order. The evaluation of the solution space reveals the wide range of possible
lens configurations covered by this analytic design method. Ray tracing analysis for calculated 20th order Taylor
polynomials demonstrate excellent performance and the versatility of this new analytical optics design concept.
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3D imaging systems are currently being developed using liquid lens technology for use in medical devices as well as in
consumer electronics. Liquid lenses operate on the principle of electrowetting to control the curvature of a buried
surface, allowing for a voltage-controlled change in focal length. Imaging systems which utilize a liquid lens allow
extraction of depth information from the object field through a controlled introduction of defocus into the system. The
design of such a system must be carefully considered in order to simultaneously deliver good image quality and meet the
depth of field requirements for image processing. In this work a corrective model has been designed for use with the
Varioptic Arctic 316 liquid lens. The design is able to be optimized for depth of field while minimizing aberrations for a
3D imaging application. The modeled performance is compared to the measured performance of the corrected system
over a large range of focal lengths.
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This paper presents the design of a multi-channel imaging system which has a different angular resolution and field of
view in the different channels. Our aim was to design a multi-resolution imaging system that can be fabricated at wafer
scale to obtain a compact and low cost imaging device. This imaging system is able to resolve fine details of a small
region of interest and control the surrounding region at the same time. An interesting aspect of such a multi-channel,
multi-resolution imaging system is that it allows to implement different image processing algorithms at different
segments of the image sensor for several imaging functionalities. We have designed an imaging system that has three
optical channels where each optical channel consists of four aspheric lens surfaces. The design was analyzed and
optimized with CODE V optical design software. The three optical channels share one image sensor which has 1440×960
pixels and a pixel size of 10μm. The first optical channel has the highest angular resolution (0.0096°) and smallest field-of-
view (2×3.5°).The third optical channel has the highest field of view (2×40°) and lowest angular resolution (0.078°).
The second optical channel has intermediate imaging properties between the first and the third optical channels;
however, it has the same image sensor segment size as the first channel. All the three optical channels have diffraction
limited performance ensuring good overall image quality.
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Ambilight is a unique Philips feature, where RGB LEDs are used to create a dynamic light halo around the television.
This extends the screen and hence increases the viewing experience, as it draws the viewer more into the action on the
screen. The feature receives very positive consumer feedback. However, implementing Ambilight in the increasingly
stringent design boundary conditions of a slim and thin TV set is a challenging task. Optical simulations play a vital role
in each step of the Ambilight development. Ranging from prototype to final product, we use simulations, next to
prototyping, to aid the choice of LEDs, optical materials and optical systems during different phases of the design
process. Each step the impact of the optical system on the mechanical design and TV set dimensions needs to be taken
into account. Moreover, optical simulations are essential to guarantee the required optical performance given a big
spread in LED performance, mechanical tolerances and material properties. Next to performance, optical efficiency is
also an important parameter to evaluate an optical design, as it establishes the required number of LEDs and the total
LED power. As such optical efficiency defines the thermal power which needs to be dissipated by the LED system. The
innovation roadmap does not stop here. For future systems we see a miniaturization trend, where smaller LED packages
and smaller dies are used. This evolution makes the impact of mechanical tolerances on the optical design more severe.
Consequentially, this approach poses a whole new challenge to the way we use optical simulations in our design process.
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For imaging design aberration theory provides solid ground for the layout and development of optical systems. Together
with general design rules it will guide the optical engineer towards a valid starting point for his system. Illumination
design is quite different: Often first system layouts are based on experience, rather than on a systematic approach. In
addition radiometric nomenclature and definitions can be quite confusing, due to the variety of radiant performance
definitions. Also at a later stage in the design, the performance evaluation usually requires extensive statistical raytracing,
in order to confirm the specified energetic quantities. In general it would therefore be helpful for illumination
designers, especially beginners, to have an engineering tool, which allows a fast, systematic and illustrative access to
illumination design problems. We show that phase space methods can provide such a tool and moreover allow a
consistent approach to radiometry. Simple illustrative methods can be used to layout and understand even complex
illumination components like integrator rods and optical arrays.
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LEDs have many advantages over traditional lighting, such as high brightness, small size, broad range of wavelengths
being emitted and ability to be placed with high density over flat or even-shaped surface. This offers promising choice
for many industrial and consumer applications and especially important for machine vision applications, where bright
and homogeneous illumination offers better visibility of features of interest. This can be obtained both with
multicomponent source configuration and analysis of distribution of optical energy density and color on an illuminated
surface. Required illuminating properties are produced by multicomponent source with certain structure and power
configuration. In this paper it is shown how to obtain required color and energy distribution on the surface of interest by
varying parameters of multicomponent source (matrix dimension, the distance between elements in the matrix, the
distance between the source and illuminated surface, etc.). Superposition of individual elements spectra is also taken into
account. This paper has proposed technique of the RGB multicomponent source simulation, which provides
homogeneous illumination on a flat surface of interest both in optical energy density and color. The ripple of luminance
on the surface shouldn't exceed the value of 2%.
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Thermo-optical simulation is a compulsory improvement of classical ray tracing, since many branches of optical and
laser technology have to deal with thermal gradients. This paper discusses an approach for coupling FEM and ray tracing
simulation tools by processing FE data using scattered data approximation techniques. The implemented interface for
two space dimensions is being validated by comparing approximated data to measured values from a CO2 laser
application of up to 1.75 kW. Finally, the benefits and further developments of analyzing thermal gradients in optical
simulation are being discussed.
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Leonhardt demonstrated (2009) that the 2D Maxwell Fish Eye lens (MFE) can focus perfectly 2D Helmholtz waves of
arbitrary frequency, i.e., it can transport perfectly an outward (monopole) 2D Helmholtz wave field, generated by a point
source, towards a "perfect point drain" located at the corresponding image point. Moreover, a prototype with λ/5 super-resolution
(SR) property for one microwave frequency has been manufactured and tested (Ma et al, 2010). Although this
prototype has been loaded with an impedance different from the "perfect point drain", it has shown super-resolution
property. However, neither software simulations nor experimental measurements for a broad band of frequencies have
yet been reported. Here we present steady state simulations for two cases, using perfect drain as suggested by Leonhardt
and without perfect drain as in the prototype. All the simulations have been done using a device equivalent to the MFE,
called the Spherical Geodesic Waveguide (SGW). The results show the super-resolution up to λ/3000, for the system
loaded with the perfect drain, and up to λ /500 for a not perfect load. In both cases super-resolution only happens for
discrete number of frequencies. Out of these frequencies, the SGW does not show super-resolution in the analysis carried
out.
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We present numerical simulations, based on elementary mode method, of field emitted by broad-area laser diodes.
The near field is expressed as a superposition of modes with sinusoidal spatial amplitude inside the laser resonator
and zero outside. The assumed functional form of the modes is used to find the intensity distribution in the
far-zone. This information is then used to construct the elementary-mode decomposition in the near-field. The
validity of the elementary-mode approach was verified by comparing the intensity and the degree of coherence
at various distances from the source.
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The propagation of harmonic fields through homogeneous media is an essential simulation technique in optical
modeling and design by field tracing, which combines geometrical and physical optics. For paraxial fields the
combination of Fresnel integral and the Spectrum of Plane Waves (SPW) integral solves the problem. For non-
paraxial fields the Fresnel integral cannot be applied and SPW often suffers from a too high numerical effort. In
some situations the far field integral can be used instead, but a general solution of the problem is not known.
It is useful to distinguish between two basic cases of non-paraxial fields: 1) The field can be sampled without problems in the space domain but it is very divergent because of small features. A Gaussian beam with large
divergence is an example. 2) The field possesses a smooth but strong phase function, which does not allow its
sampling in space domain. Spherical or cylindrical waves with small radius of curvature are examples. We refer
to such fields as fields with a smooth phase term. The complete phase is the sum of the smooth phase term and
the residual.
For both cases we present a parabasal field decomposition, in order to propagate the field. In the first case
we perform the decomposition in the Fourier domain and in the second case in the space domain. For each of the
resulting parabasal fields we separate a linear phase factor which has not to be sampled. In order to propagate
the parabasal fields we present a rigorous semi-analytical SPW operator for parabasal fields, which can handle
the linear phase factors without sampling it at any time. We show that the combination of the decomposition
and this modified SPW operator enables an ecient propagation of non-paraxial fields.
All simulations were done with the optics software VirtualLab™.
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The propagation of harmonic fields between non-parallel planes is a challenging task in optical modeling. Many
well-known methods are restricted to parallel planes. However, in various situations a tilt of the field is demanded,
for instance in case of folded setups with mirrors and tolerancing with tilted components. We propose a rigorous
method to calculate vectorial harmonic fields on tilted planes. The theory applies a non-equidistant sampling
in the k-space of the field before rotation in order to obtain an equidistant sampling of the rotated field. That
drastically simplifies the interpolation challenge of the tilt operation. The method also benefits from an analytical
processing of linear phase factors in combination with parabasal field decomposition. That allows a numerically
efficient rotation of any type of harmonic fields. We apply this technique to the rigorous propagation of general
harmonic fields through plane interfaces. This propagation can be based on a plane wave decomposition of the
field. If the field is known on the interface a fast algorithm results from the decomposition. However in general,
the field is not known on the interface. Then a rotation operator must be applied first. All simulations were
done with the optics software VirtualLab™.
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This article deals with an optical model which describes silicon thin film solar cells with rough interfaces in a fast and
easy way. In order to simulate thin layer stacks with rough interfaces diffuse scattering as well as interference effects
have to be taken into account. Algorithms like the Finite-Difference Time-Domain method (FDTD) solve the Maxwell
Equations and therefore fulfil these demands. Yet they take up a considerable amount of simulation time and
computation capacity. To overcome these drawbacks an optical model was developed which combines the Transfer-
Matrix-Method (TMM) and the Raytracer algorithm. The fraction of TMM and Raytracer in the model is determined by
a separating function which can be interpreted as the integral haze. In order to verify the combined optical model a series
of amorphous silicon single cells with varying intrinsic layer thicknesses was produced on two different kinds of textured
substrates. The results of the combined optical model are compared to measured data as well as to the simulation results
of the FDTD method. It can be shown that the combined optical model yields good results at low simulation time.
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The development of photonic devices with tailor-made optical properties requires the control and the manipulation of
light propagation within structures of different length scales, ranging from sub-wavelength to macroscopic dimensions.
However, optical simulation at different length scales necessitates the combination of different simulation methods,
which have to account properly for various effects such as polarization, interference, or diffraction: At dimensions much
larger than the wavelength of light common ray-tracing (RT) techniques are conveniently employed, while in the subwavelength
regime more sophisticated approaches, like the so-called finite-difference time-domain (FDTD) technique,
are needed. Describing light propagation both in the sub-wavelength regime as well as at macroscopic length scales can
only be achieved by bridging between these two approaches.
In this contribution we present on the one hand a study aiming at the determination of the intermediate size range for
which both simulation methods are applicable and on the other hand an approach for combining classical ray-tracing
with FDTD simulation in order to handle optical elements of large sizes. Generally, the interface between RT and FDTD
is restricted to very small sample areas. Nevertheless, many real world optical devices use e.g. diffractive optical
elements (DOEs) having comparably large areas in the order of 1-2 mm² (or larger). Therefore, one has to develop
strategies in order to handle the data transfer between FDTD and RT also for structures of such larger size scales. Our
approach in this regard is based on the symmetries of the structures. In this way support programs like e.g. MATLAB
can be used to replicate the near-field of a single structure and to merge it to the near-field of a larger area. Comparisons
of RT and FDTD simulations in the far-field can be used to validate the physical correctness of this approach. With such
procedure it is possible to optimize light propagation effects at both the macro- and microscale and to exploit their whole
potential for the manipulation and optimization of optical and photonic devices.
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The objective of this paper is to investigate nonlinear effects in Wavelength-Division Multiplex (WDM) systems in the
case when different types of high-order M-PSK and M-QAM modulation formats for various structures of channel
spacing are used optical signals. In general, the degradation mechanisms are caused by transmitted optical signals and
their impact on each optical channel in WDM can be very different. Therefore, it is suitable to investigate possibilities
for channel arrangement from the point of view of equidistant and non-equidistant channel spacing, respectively, what
would lead to the suppression of nonlinear effects. In this article we investigate new types of high-order modulation
formats that have ability for increasing of spectral efficiency and total improvement of performance of the transmission
WDM system. The attention is put on two classes of channel spacing in WDM system, equidistant channel spacing
(Δf = 100, 50, 25 and 12.5 GHz) and non-equidistant channel spacing (Δf ≠ const.), respectively. For investigation of
signal propagation the numerical model is created. The model is based on mathematical method Symmetrical-Split Step
Fourier Method (S-SSFM), which is utilized for solving the coupled nonlinear Schrödinger's equations (CNLSE)
describing the transmission of signals in multichannel systems. The results of the created numerical model are analyzed,
compared to each other and interpreted in a way that leads to the determination of suitable high-order modulation
formats and we try to propose the optimal arrangement of optical channels in WDM system. The key issue is to suppress
the impact of nonlinearities on modulated signals for each channel with respect to the employed types of digital
modulation formats, various system parameters, different types of optical fibers and localization of reference channel in
the wavelength area.
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In this paper we present the experimental generation of complex beams by means of a polarization holographic
technique. The interference of a reference Gaussian beam and a complex beam having opposite circular polarization
states, stored on a highly polarization sensitive material, generates polarization holograms whose diffracted beams are
high quality complex fields. The technique is tested with the generation of three different types of beams: a simple
vortex, a Bessel and a Laguerre-Gaussian beam. This suggests an alternative method for the generation of complex
beams with predetermined polarization states.
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With the ever-increasing prevalence of minimally invasive procedures (MIP) in the medical world, the designing of
endoscopes, essential in MIP, becomes more and more challenging. As the continuous and ubiquitous need for
miniaturization is starting to outmatch the possibilities offered by the combination of conventional fibre optics and
micro-optics, novel approaches are necessary in order to ensure the advancement of endoscopy and consequently of MIP.
In conventional fibre bundles the phase-relation between cores is not conserved during the propagation of an electrical
field and as such extra micro-optics at the distal end are necessary in order to be able to focus or scan the exiting light or
achieve a certain field of view (FOV). In this paper we analyze the requirements and constraints for a multi-core optical
fibre (MCF) which conserves the phase relationship between the cores. With such a phase conserving MCF, focusing
and scanning light at the distal end could be done by shaping the wavefront through adaptive optics before coupling the
light into the fibre therefore making extra micro-optics superfluous.
Using numerical and mode solving simulations we investigate the relationship between the size, the period and the
numerical aperture of the cores on the one hand and the focal point and field of view on the other hand. We show that
there is a non-circumventable trade-off between intercore crosstalk and the FOV. In addition, we determine the effects
on the focusing ability and on the FOV of deviations of core size and period, due to fabrication errors. Using this
knowledge, we propose two designs for the phase conserving MCF. The first design allows for focusing and scanning the
exiting light but is sensitive to deviations in core size and separation. The second design is less sensitive to fabrication
errors but can only focus and not sweep.
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In this study, a tool was developed to calculate the bulk optical properties for systems consisting of an absorbing medium
and polydisperse spherical particles that can scatter and/or absorb. The developed tool is based on the Mie-theory for
monodisperse-spherical absorbing and scattering particles in vacuum. First, the original Mie-theory was expanded to also
include physical (real part of refractive index) and chemical (aborption, imaginary part of refractive index) information
of the host medium. Secondly, the polydispersity of the spherical particles was taken into account. Since particle size
distributions (PSD) are typically continuous distributions and Mie-scattering properties can only be calculated for a
monodisperse system, the PSD is fractionated and Mie-scattering properties were calculated for each fraction. These
Mie-scattering properties are then combined with the weight for each fraction to derive bulk optical properties. As the
number of fractions is unknown and needs to be optimized for each calculation, the developed tool keeps on
fractionating until the desired properties (μabs, μsca and P11(cos(θ))) converge to stable values. This flexible tool
allows for the simulation of the bulk optical properties for a wide range of wavelengths, particle volume fractions,
complex refractive indices of both the particles and the medium and PSD's based on normal, lognormal, gamma,
bimodal and custom defined functions. This code was successfully validated for the case of a lognormal PSD of
scattering spheres in vacuum by comparing the simulated values to those reported in literature. The main novelties
of the developed program are the extension of Mie-theory simulations to the case of polydisperse scattering particles in
absorbing media and the automatic optimization of the number of PSD fractions needed to converge.
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This paper presents an adaptation of the widely accepted Monte Carlo method for Multi-layered media
(MCML). Its original Henyey-Greenstein phase function is an interesting approach for describing how light scattering
inside biological tissues occurs. It has the important advantage of generating deflection angles in an efficient - and
therefore computationally fast- manner. However, in order to allow the fast generation of the phase function, the MCML
code generates a distribution for the cosine of the deflection angle instead of generating a distribution for the deflection
angle, causing a bias in the phase function. Moreover, other, more elaborate phase functions are not available in the
MCML code.
To overcome these limitations of MCML, it was adapted to allow the use of any discretized phase function. An
additional tool allows generating a numerical approximation for the phase function for every layer. This could either be a
discretized version of (1) the Henyey-Greenstein phase function, (2) a modified Henyey-Greenstein phase function or (3)
a phase function generated from the Mie theory. These discretized phase functions are then stored in a look-up table,
which can be used by the adapted Monte Carlo code.
The Monte Carlo code with flexible phase function choice (fpf-MC) was compared and validated with the original
MCML code. The novelty of the developed program is the generation of a user-friendly algorithm, which allows several
types of phase functions to be generated and applied into a Monte Carlo method, without compromising the
computational performance.
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The Talbot-Lau arrangement is an optical system using two gratings of different pitches. The gratings are placed parallel
with some distance separated. By illuminating them with a broad incoherent source, we obtain high contrast grating
images formed on a plane at a distance determined by the pitches. The phenomenon is called generalized grating
imaging. It is used, for example, in pattern projection profilometer and as a shearing interferometer for light, X-ray and
matter waves. There are many analyses on the Talbot-Lau arrangement. However, almost all of them are related to onedimensional
gratings. This paper presents a rigorous analysis on the phenomenon with two-dimensional gratings using
wave optics. The analytical result is applied to hexagonal gratings and the contrast is calculated by numerical calculation.
The numerical results agree with experimental results. The analysis can be used to design a Talbot-Lau arrangement with
two-dimensional gratings in broad fields.
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The B-spline modal method is adapted for the design and analysis of nanostructured devices in conical mounting.
The eigenmodes in each layer are calculated for two specific polarization states, and then combined for the
calculation of the scattering matrices. We take advantage of the sparsity of the generated matrices to decrease
the computation time, and adress the need for fast computation in complex systems. Moreover, we demonstrate
the physical interest of computing the conical response on various classical structures.
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A technique for flattening the chromatic dispersion in silicon nitride waveguides with silica cladding is proposed and
numerically investigated. By modifying the transversal dimensions of the silicon nitride core and by adding several
cladding layers with appropriate refractive indices and thicknesses, we demonstrate dispersion flattening over large
spectral bandwidths in the near infrared. We analyze several cladding refractive index profiles that could be realistically
fabricated by using existing materials and doping procedures.
We show that cladding engineering allows for much more dispersion control (and flattening) in comparison with
optimizing only the core transversal dimensions. For the latter case it is demonstrated that while the zero dispersion
wavelength can be shifted to a great extent, the effect of the cross-section adjustment in the flatness is very limited. In
sharp contrast, by adding two cladding layers and decreased refractive index values, the dispersion ripple can be strongly
reduced. By further adding one more layer and by adjusting their refractive indices it is possible to obtain nearly constant
chromatic dispersion (only +/- 3 ps/nm-km variation) over the spectral region from 1.8 to 2.4 microns. In our
calculations, the analyzed change in the silica or silicon nitride refractive index is up to +/-3%. Our technique should
open new avenues for the demonstration of high-performance nonlinear devices on a chip. Furthermore highly dispersive
integrated photonic components can be envisaged for slow light applications and integrated photonics spectrographs.
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The paper presents theoretical and experimental investigations of light beam self-trapping in a photorefractive
medium based on Plexiglas (polymethylmethacrylate, PMMA) with photosensitive phenanthrenequinone (PQ)-
molecules. It is shown that the self-trapping of a laser beam is generated due to the self-interaction of the propagating
light wave under the conditions of a well balanced concurrence of the effects of light diffraction and nonlinear focusing.
A new method for controlling the waveguide cross-section by changing the ratio of two competing mechanisms of the
nonlinear refractive-index variation (namely the formation of the photoproducts and the heating of the medium while
varying the power of the light beam) is proposed.
The recording of self-trapping structures implemented in PQ-PMMA layers has been realized with two laser sources
(405 nm and 514.5 nm) with an average power of several mW. It is shown that the photoattachment of the PQ-molecules
to the polymeric chains and the formation of the photoproduct play the decisive role for the light-induced increase of the
refractive index. Besides, the formation of the waveguide is strongly influenced by heating of the medium, which results
in an additional thermal defocusing of the light beam.
It has been established that the parameters of the waveguide (cross-section and length) are strongly dependent on the
wavelength and the power of the laser radiation, as well as on the concentration of the PQ-molecules. Waveguiding
structures with a diameter of 100 μm were recorded in samples with a high PQ-concentration (up to 4 mol.%) for the
wavelength of 514.5 nm. Reducing the dye-concentration by one order requires shorter (blue) wavelengths (405 nm).
The dependence of the waveguide parameters and the optimal laser wavelength on the concentration of PQ-molecules is
confirmed by the numerical calculation including a 3D-model of the light self-trapping.
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Speckle fields are formed when quasi-monochromatic light is scattered by an optically rough surface. These fields
are usually described by reference to their first and second order statistical properties. In this paper we review
and extend some of these fundamental properties and propose a novel technique for estimating the refractive
index of a smooth sample. Theoretical and experimental results are presented. Separately, we also report on
a preliminary experiment to determine some characteristics of speckle fields formed in free space by a rotating
compound diffuser. Some initial measurements are made where we examine how the speckle intensity pattern in
the output plane changes as a function of the relative rotation angle.
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Recently, the development of optical setups capable of generating beams with arbitrary polarization have attracted
broad interest. One possible way to implement such devices is by taking advantage of the properties
of liquid crystal spatial light modulators, which act as optical phase retarders controlled by computer. In this
communication we present the design of an alternative experimental setup for the generation of light beams
with arbitrary spatially-variant polarization distribution. The objective is to develop a flexible optical device
capable of dynamically encode any elliptical polarization state in each point of the wavefront. Our approach is
based on a Mach-Zehnder setup combined with a translucent modulator in each path of the interferometer. The
transverse beam components of the incident light beam are processed independently, and modified by means of
their respective modulator displaying a specifically tailored computer generated phase hologram.
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An exact synthesis algorithm for dielectric thin film filters with uniform optical phase thickness was first presented
in 2004. This algorithm computes at least one thin film stack which realizes a given filter function. The feasibility
is guaranteed by a set of necessary and sufficient conditions the filter function has to fulfill. This set of conditions
only guarantees strictly positive refractive index values for all thin film layers. For a technological realization
strictly positive refractive index values are insufficient since only certain refractive index values can be realized
for a thin film layer.
In this paper an additional condition for the location of the zeros of the filter response function is derived.
Starting point is a boundary condition for the refractive index value for each of the N layers of the filter stack.
Each refractive index value can be selected arbitrarily from an interval which is bounded by a lower and an upper
refractive index boundary value. This additional zero location condition is necessary that at least one filter stack
exists which fulfills these boundary conditions to a given filter function.
Since the boundary conditions are determined by the used fabrication process for thin film filters the presented
additional condition for the location of the zeros has to be calculated only once when a new process is installed.
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Numerical calculations with nite-dierence time-domain (FDTD) on metallic nanostructures in a broad optical
spectrum require an accurate approximation of the permittivity of dispersive materials. In this paper, we present
the algorithms behind B-CALM (Belgium-California Light Machine), an open-source 3D-FDTD solver operating
on Graphical Processing Units (GPUs) with multi-pole dispersion models. Our modied architecture shows a
reduction in computing times for multi-pole dispersion models. We benchmark B-CALM by computing the
absorption eciency of a metallic nanosphere on a broad spectral range with a six-poles Drude-Lorentz model
and compare it with Mie theory.
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Through numerical simulations we have shown that particle plasmon resonance wavelength is dependent mostly
on the largest particle in an array of gold nanodisks. Mixing different sized nanodisks may shift the resonance
peak wavelength from a few nanometers to tens of nanometers. The effect of period to the resonance peak
strength was found to be dependent on the disk diameter in unexpected way. With smaller nanodisks increasing
the period decreases peak absorption, but with larger still greatly sub-wavelength particles increasing the period
can increase the absorption at resonance peak while decreasing absorption elsewhere on the spectrum giving
great selective contrast.
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Multi-dielectric coatings are designed to reach total absorption and maximum field amplification at resonances under
total reflection. The design method is analytic and numerical results are given. Comparison with plasmons or thin
metallic layers is discussed. Scattering from these coatings is investigated for measurements of amplification.
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Recent developments in design algorithm enable to design freeform surfaces that generate intensity distributions
with middle to high spatial frequency. Such freeform surfaces can generate a picture in a defined plane. In
contrast to conventional imaging, the light modulation is done by a ray-optical redistribution of the incident light
comparable to incoherent beam shaping. Such picture-generating freeform surfaces have various advantages. As
only one single optical element is needed to generate the intensity distribution, very compact optical systems can
be designed. Additionally, they are highly energy efficient, as nearly 100% of the incident light is directed into the
image plane. In case of a freeform mirror, the system is wavelength independent, which offers the possibility for
applications in UV or IR spectral range, as well as the polychromatic projection without any chromatic aberration.
As no classical imaging is performed, conventional evaluation criteria concerning the resolution of this picturegenerating
system like e.g. the Rayleigh criterion cannot be applied. In order to simulate diffraction effects in
the picture plane, the wave-optical propagation has to be simulated. However, depending on the geometrical
arrangement of such systems, the surface modulation of the freeform can be up to several millimeters. This
leads to a violation of the thin element approximation and to significant sampling problems using conventional
propagation algorithms. Therefore, we used a propagation method based on the Huygens-Fresnel principle. The
physical formation of the intensity distribution of a picture-generating freeform system was simulated and the
diffraction limit evaluated. We will show that such systems have a significantly lower resolution than conventional
imaging systems. However, they are very well suited for middle- and low-resolution applications.
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The effect of internal conical refraction in biaxial crystals is applied for transforming the lowest-order Gaussian
laser beams into optical vortex beams and annular beams with radial and azimuthal polarization. The evolution
of the emerging vortex beams upon propagation is analyzed and compared with the reference Laguerre-Gauss
beam. The formation of beams with radial and azimuthal polarization with the aid of two biaxial crystals placed
into the arms of a Mach-Zehnder interferometer is demonstrated.
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A novel fly's eye homogenizer for single mode laser diodes is presented. Laser speckle has been removed and a uniform laser line illumination has been obtained for the first time with the proposed fly's eye homogenizer incorporating a single mode laser diode by introducing a staircase element and short pulse switching of the injection current. The former degrades the spatial coherence of the adjacent beamlets emanating from the microlens arrays while the latter simultaneously shortens the temporal coherence time so that the necessary optical path lengths in the staircase element become realistic in size. An average speckle contrast of 5% was achieved with the new fly's eye homogenizer whereas the standard fly's eye homogenizer at a CW driving yielded a high contrast of 87%. The diffraction theory for partial coherent light based on Wolf's formulation was extended to a simplified model of the new fly's eye homogenizer. The effect of the pulse width on the speckle contrast of the laser line illumination is experimentally shown and is discussed through a detailed analysis of the power spectrum and the fringe visibility, and a numerical study on the Dirichlet kernel based on the derived formulation for the intensity.
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Low-height camera modules are demanded for such applications as cellular phones and vehicles. For designing optical
lens, it has widely been recognized that a trade-off exists between reducing the number of lenses and camera resolution.
The optical performance of imaging lenses has been improved by diffraction gratings, which have a peculiar inverse
dispersion in the wavelength and exhibit the efficacy of correction for chromatic aberration. We can simultaneously
reduce the number of lenses and maintain optical resolution using diffraction gratings.
However, we have found a generation of striped flare lights under intense light sources that differ from unnecessary
order diffraction lights. In this paper, we reveal the generation mechanism of these new striped diffraction lights and
suggest a novel structure of diffraction gratings that can decrease them.
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An InfraRed (IR) cooled camera is generally composed by an optical block (warm lenses outside a dewar) and a
detection block (a cooled focal plane array inside the dewar). A minimalist approach to design a compact and robust
camera consists in giving the dewar an imaging function by replacing the cold pupil by a Diffractive Optical Element
(DOE). In this paper we present different DOE that can be used to design the camera. We present first a pinhole camera
that validates this approach but that is limited in radiometric performances and in angular resolution. We replace then the
pinhole by a continuously self-imaging DOE, such as the diffractive axicon, to improve both the radiometric
performances and the angular resolution. Finally, the MALDA is introduced to improve the performances of the axicon.
Diffraction effects and Talbot effect under polychromatic light are exposed for such DOE and two different design rules
are derived from those effects to allow the design of a compact camera with dimensions compatible with the size of an
industrial dewar. Experimental prototypes are presented and radiometric performances are compared and show the best
performances for the MALDA.
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We report on holographic storage of digital data pages in a thick silica nanoparticle-polymer composite film
that uses step-growth thiol-ene photopolymerization at a wavelength of 532 nm. Shift-multiplexed holographic
storage of 180 digital data pages with a two-dimensional 2:4 modulation code was successfully demonstrated
with low symbol-error rates. This result clearly shows the feasibility of the thiol-ene based nanoparticle-polymer
composite system as holographic data storage media.
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We report on a statistical thermodynamic simulation of holographic photopolymerization in a holographic
polymer-dispersed liquid crystal under holographic exposure. We employ the dynamic density functional theory
to study the spatio-temporal evolution of monomer, polymer and liquid crystal distributions as continuous density
order parameters in numerical simulations. Density-dependent mutual diffusion of monomer, polymer and
liquid crystals are taken into account under the constraints of the mass conservation and the incompressibility
conditions by using the Lagrange multiplier method. The autocatalytic model is employed to describe the photopolymerization
kinetics. The simulation results are compared with measured results such as the average size
of liquid crystal droplets and a grating-spacing dependence of the formed refractive index modulation.
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The Non-local Photo-Polymerization Driven Diffusion (NPDD) model was introduced to describe the observed drop-off
in the material's response for higher exposing spatial frequencies. Recent work carried out on the modeling of the
mechanisms which occur in photopolymers during- and post-exposure, has led to the development of a tool, which can
be used to predict the behaviour of these materials under a wide range of conditions. In this article, based on the
chemical reactions of chain transfer agents, we explore this extended NPDD model, illustrating some of the useful trends,
which the model predicts and we analyse their implications on the improvement of photopolymer material performance.
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A new low-toxicity diacetone acrylamide-based photopolymer is developed and characterized. The environmentallycompatible
photopolymer has been modified with the inclusion of glycerol. The incorporation of glycerol results in a
uniform maximum refractive index modulation for recording intensities in the range of 1-20 mW/cm2. This may be
attributed to glycerol's nature as a plasticizer, which allows for faster diffusion of un-reacted monomer within the grating
during holographic recording. An optimum recording intensity of 0.5 mW/cm2 is observed for exposure energies of 20-
60 mW/cm2. The modified photopolymer achieves a refractive index modulation of 2.2×10-3, with diffraction efficiencies
up to 90 % in 100 μm layers. The photopolymer layers containing glycerol have improved stability and optical quality.
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An understanding of the photochemical and photo-physical processes, which occur during photo-polymerization, is of
extreme importance when attempting to improve a photopolymer material's performance for a given application.
Recent work carried out on the modeling of photopolymers during- and post-exposure, has led to the development of a
tool, which can be used to predict the behavior of a number of photopolymers subject to a range of physical conditions.
In this paper, we explore the most recent developments made to the Non-local Photo-polymerization Driven Diffusion
model, and illustrate some of the useful trends, which the model predicts and then analyze their implications on
photopolymer improvement.
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Over the past century, monitoring of Giardia lamblia became a matter of concern for all drinking water suppliers
worldwide. Indeed, this parasitic flagellated protozoan is responsible for giardiasis, a widespread diarrhoeal disease (200
million symptomatic individuals) that can lead immunocompromised individuals to death. The major difficulty raised by
Giardia lamblia's cyst, its vegetative transmission form, is its ability to survive for long periods in harsh environments,
including the chlorine concentrations and treatment duration used traditionally in water disinfection. Currently, there is a
need for a reliable, inexpensive, and easy-to-use sensor for the identification and quantification of cysts in the incoming
water.
For this purpose, we investigated the use of a digital holographic microscope working with partially coherent spatial
illumination that reduces the coherent noise. Digital holography allows one to numerically investigate a volume by
refocusing the different plane of depth of a hologram.
In this paper, we perform an automated 3D analysis that computes the complex amplitude of each hologram, detects all
the particles present in the whole volume given by one hologram and refocuses them if there are out of focus using a
refocusing criterion based on the integrated complex amplitude modulus and we obtain the (x,y,z) coordinates of each
particle. Then the segmentation of the particles is processed and a set of morphological and textures features
characteristic to Giardia lamblia cysts is computed in order to classify each particles in the right classes.
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We developed a new off-axis digital holographic microscope (DHM), working in transmission with a RGB LED
illumination. This partially coherent multi-wavenlenght source gives a low noise holograms and the intensity image
quality is fully exploitable for microscopy purposes. We implemented a full off-axis configuration enables the recording
of the holographic data in one shot. As we used for the first tests a monochromatic CCD camera, the holograms are
recorded separately in each spectral channel. The holograms are individually processed by the Fourier method to obtain,
in each color, the complex amplitudes and the corresponding intensities and optical phases. The color intensities are
recombined to obtain a composite RGB color image. The digital holographic refocusing and the optical phase map
computation are successfully demonstrated. The multi-wavelengths operation provides a significant improvement of the
collected information for colored samples. The full one-shot color hologram recording should be available with a color
camera.
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We propose a new Iterative Fourier Transform Algorithm (IFTA) capable to suppress ghost traps and noise in
Holographic Optical Tweezers (HOT), maintaining a high diffraction efficiency in a computational time comparable
with the others iterative algorithms. The process consists in the planning of the suitable ideal target of optical tweezers as
input of classical IFTA and we show we are able to design up to 4 real traps, in the field of view imaged by the
microscope objective, using an IFTA built on fictitious phasors, located in strategic positions in the Fourier plane. The
effectiveness of the proposed algorithm is evaluated both for numerical and optical reconstructions and compared with
the other techniques known in literature.
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We propose a new denoising algorithm in off-axis Digital Holography (DH) based on l1 norm minimization. The aim of
our work is to assess a general denoising scheme of digital holograms, i.e. we do not explore prior knowledge of the
statistics of the digital holograms. For this purpose, we consider different experimental conditions such as a digital
holograms recorded in microscope configuration and lensless configuration. We use the inherent sparsity of the
numerical reconstruction of digital holograms in order to optimize the in-focus digital reconstructions. For this reason,
we call the proposed algorithm SPADEDH (SPArsity DEnoising of Digital Holograms). We perform also a display test,
by using a Spatial Light Modulator (SLM) as a projection system, for the digital holograms recorded in lensless
configuration. In both numerical reconstruction and display test, the improvements of the SPADEDH algorithm are
computed.
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The Smart X-Ray Optics (SXO) project comprises a UK-based consortium developing active/adaptive micro-structured
optical arrays (MOAs). MOA devices are designed to focus X-rays using grazing incidence reflection through
consecutive aligned arrays of microscopic channels. Adaptability is achieved using a combination of piezoelectric
actuators, which bend the edges of the silicon chip, and a spider structure, which forms a series of levers connecting the
edges of the chip with the active area at the centre, effectively amplifying the bend radius.
The spider actuation concept, in combination with deep silicon etching stopped close to the surface, can also be used to
create deformable mirrors where the curvature and tip/tilt angles of the mirror can be controlled. Finite Element Analysis
(FEA) modelling, carried out for the optimization of the spider MOA device, indicates that deformable mirrors with
curvature varying from flat to 5cm ROC and control over the tip/tilt angles of the mirror of +/-3mrad could be achieved.
Test spider structures, manufactured using a Viscous Plastic Processing Process for the PZT piezoelectric actuators and a
single wet etch step using <111> planes in a (110) silicon wafer for both the silicon channels and the spider structure,
have been bent to a radius of curvature smaller than 5 cm.
This paper evaluates the spider MOA's concept as a means to achieve deformable mirrors with controllable ROC and
control over the tip/tilt angles. FEA modelling results are compared with obtained characterization data of prototype
structures. Finally, manufacturing and integration methods and design characteristics of the device, such its scalability,
are also discussed.
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Digital Holographic Microscopy (DHM) is a powerful tool that strongly increases the field of investigation of classical
microscopy. It allows to be used as phase contrast microscopy with the additional information of the z position over a
whole experimental volume by acquiring a single frame. The use of a spatially reduced coherent source strongly reduces
the coherent noise.
Vesicles are close lipid membranes enclosing a sugar-water solution. Those biomimetic deformable objects are good
mechanical models of living cells such as Red Blood Cells. We investigate the dynamics of a vesicle suspension in shear
flow between walls (with a gap of about 200 μm). When vesicles are placed in a shear flow, they undergo a lift force that
pushes them away from the wall until they reach the centre of the channel where the effects of both walls are
compensated. On the other hand, hydrodynamical interactions between vesicles and segregation effects tend to push
small vesicles away from the centre of the channel. The final distribution is thus a compromise between both effects that
structures the distribution and has strong impact on rheology.
DHM with reduced coherence and specific related algorithms (phase compensation, best focus plane determination,
segmentation, ...) provide a full description of each object in the experimental volume as a function of their size and
shape. Results are provided and illustrate the quantification of the lift force and the hydrodynamical interactions (shear
induced diffusion).
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The propagation of coherent light through a heterogeneous medium is an often-encountered problem in optics. Analytical
solutions, found by solving the appropriate differential equations, usually only exist for simplified and idealized
situations limiting their accuracy and applicability. A widely used approach is the Beam Propagation Method in which
the electric field is determined by solving the wave equation numerically, making the method time-consuming, a
drawback exacerbated by the heterogeneity of the medium. In this work we propose an alternative approach which
combines, in an iterative way, optical ray-tracing simulation in the software ASAP™ with numerical simulations in
Matlab in order to model the change in light distribution in a medium with anisotropic absorption, exposed to partially
coherent light with high irradiance. The medium under study is a photosensitive polymer in which photochemical
reactions cause the local absorption to change as a function of the local light fluence. Under continuous illumination, this
results in time-varying light distributions throughout the irradiance process. In our model the fluence-absorption
interaction is modelled by splitting up each iteration step into two parts. In the first part the optical ray-tracing software
determines the new light distribution in the medium using the absorption from the previous iteration step. In the second
part, using the new light distribution, the new absorption coefficients are calculated and expressed as a set of
polynomials. The evolution of the light distribution and absorption is presented and the change in total transmission is
compared with experiments.
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Martian atmosphere contains a significant and rapidly changing load of suspended dust that never drops to zero. The
main component of Martian aerosol is micron-sized dust thought to be a product of soil weathering. Although airborne
dust plays a key role in Martian climate, the basic physical properties of these aerosols are still poorly known. The scope
of Mars MetNet Mission is to deploy several tens of mini atmospheric stations on the Martian surface. MEIGA-MetNet
payload is the Spanish contribution in MetNet. Infrared Laboratory of University Carlos III (LIR-UC3M) is in charge of
the design and development of a micro-sensor for the characterization of airborne dust. This design must accomplish
with a strict budget of mass and power, 45 g and 1 W respectively. The sensor design criteria have been obtained from a
physical model specifically developed for optimizing IR local scattering. The model calculates the spectral power density
scattered and detected between 1 and 5 μm by a certain particle distribution and sensor configuration. From model
calculations a modification based on the insertion of a compound ellipsoidal concentrator (CEC) has appeared as
necessary. Its implementation has multiplied up to 100 the scattered optical power detected, significantly enhancing the
detection limits of the sensor.
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The article presents the approach to the design wide-angle optical systems with special illumination and instantaneous
field of view (IFOV) requirements. The unevenness of illumination reduces the dynamic range of the
system, which negatively influence on the system ability to perform their task. The result illumination on the
detector depends among other factors from the IFOV changes. It is also necessary to consider IFOV in the synthesis
of data processing algorithms, as it directly affects to the potential "signal/background" ratio for the case
of statistically homogeneous backgrounds. A numerical-analytical approach that simplifies the design of wideangle
optical systems with special illumination and IFOV requirements is presented. The solution can be used
for optical systems which field of view greater than 180 degrees. Illumination calculation in optical CAD is based
on computationally expensive tracing of large number of rays. The author proposes to use analytical expression
for some characteristics which illumination depends on. The rest characteristic are determined numerically in
calculation with less computationally expensive operands, the calculation performs not every optimization step.
The results of analytical calculation inserts in the merit function of optical CAD optimizer. As a result we reduce
the optimizer load, since using less computationally expensive operands. It allows reducing time and resources
required to develop a system with the desired characteristics. The proposed approach simplifies the creation and
understanding of the requirements for the quality of the optical system, reduces the time and resources required
to develop an optical system, and allows creating more efficient EOS.
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Setup for recording digital off-axis Fresnel holograms is described. Obtained digital holograms were reconstructed both
numerically and optically. Results of optical and numerical reconstructions are compared. Digital off-axis Fresnel
holograms with a pixel size 9 μm and number of pixels up to 2048 × 2048 for the scene depth up to 480 mm at distances
700÷1400 mm were recorded. Experimental setup allows to record holograms in both modes of object's illumination:
"on transmission" and "on reflection". For hologram numerical reconstruction various methods were implemented in
programming environment MATLAB: direct calculation of Fresnel diffraction (DC), Fresnel diffraction calculation
through fractal Fourier transform (FrFT), angular spectrum propagation and others. Under numerical testing it was found
that the best quality of reconstructed images is provided by the FrFT method. The DC method yielded the best results for
numerical reconstruction of recorded digital holograms. For optical reconstruction recorded digital holograms were
binarized by the threshold and printed on transparent film with a resolution of 100 dots/mm using laser imagesetter. The
optically reconstructed images have higher noise level than numerically reconstructed ones. This is primarily because of
holograms binarization. Also digital holograms were optically reconstructed using LCOS SLM HoloEye PLUTO VIS.
Resolutions of displayed digital holograms were limited to 1920 × 1080 (SLM resolution). Quality of reconstructed
images is close to quality of numerically reconstructed images. Real time holographic video of remote volumetric scenes
was experimentally demonstrated through combination of the setup for digital holograms recording and the setup with
SLM for their optical reconstruction.
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In our work we demonstrate a computational method of phase retrieval realized for various propagation models. The
effects, arising due to the wave field propagation in an optical setup, lead to significant distortions in measurements;
therefore the reconstructed wave fields are noisy and corrupted by different artifacts (e.g. blurring, "waves" on boards,
etc.). These disturbances are hard to be specified, but could be suppressed by filtering. The contribution of this paper
concerns application of an adaptive sparse approximation of the object phase and amplitude in order to improve imaging.
This work is considered as a further development and improvement of the variational phase-retrieval algorithm
originated in 1. It is shown that the sparse regularization enables a better reconstruction quality and substantial
enhancement of imaging. Moreover, it is demonstrated that an essential acceleration of the algorithm can be obtained by
a commodity graphic processing unit, what is crucial for processing of large images.
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Accurate modeling of dynamic optical interactions such as saturation and re-absorption in highly doped
waveguide amplifiers requires solving a stiff system of ordinary differential equations (ODEs). Traditional
ODE solvers including Range-Kutta methods are computationally ill-suited for such applications. In this
paper, we derive and apply predictor - corrector adaptive Adam-Bashforth scheme for modeling the population
dynamics in Erbium - Doped Fiber Amplifiers (EDFA). Predictor and corrector equations for adaptive
Adam-Bashforth have been derived by using Lagrange polynomial as basis rather than the Newton polynomials
used in constant stepsize Adam-Bashforth scheme. Convergence and stability analysis conducted
on the scheme shows that the method has similar characteristics as that of constant step-size conventional
Adam-Bashforth methods for small changes in step sizes. Solutions have been validated by re-generating
the absorption and emission coefficients for doped fibers with two different doping concentrations, which
is found to match with the manufacturer datasheet. This method is compared with other method like Euler
and the optimum order of predictor and corrector is estimated. The result show that this modified form of
the scheme results in 75% reduction in step-size to maintain an relative accuracy level of 10-3 as compared
to adaptive Euler method. Finally, different orders were compared by using ratio of step-size and number
of operations per step as a metric for Figure of Merit (FOM). FOM analysis shows that use of higher order
methods are not efficient in reducing the number of steps required to obtain accurate results. It is found that
the scheme with both second order predictor and corrector is the most efficient computationally. However,
in terms of accuracy second order predictor and third order corrector is more suitable with only a marginal
degradation of FOM.
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Method of optical image coding by time integration is proposed. Coding in proposed method is accomplished by
shifting object image over photosensor area of digital camera during registration. It results in optically calculated
convolution of original image with shifts trajectory. As opposed to optical coding methods based on the use of diffractive
optical elements the described coding method is feasible for implementation in totally incoherent light. The method was
preliminary tested by using LC monitor for image displaying and shifting. Shifting of object image is realized by
displaying video consisting of frames with image to be encoded at different locations on screen of LC monitor while
registering it by camera. Optical encoding and numerical decoding of test images were performed successfully. Also
more practical experimental implementation of the method with use of LCOS SLM Holoeye PLUTO VIS was realized.
Objects images to be encoded were formed in monochromatic spatially incoherent light. Shifting of object image over
camera photosensor area was accomplished by displaying video consisting of frames with blazed gratings on LCOS
SLM. Each blazed grating deflects reflecting from SLM light at different angle. Results of image optical coding and
encoded images numerical restoration are presented. Obtained experimental results are compared with results of
numerical modeling. Optical image coding with time integration could be used for accessible quality estimation of
optical image coding using diffractive optical elements or as independent optical coding method which can be
implemented in incoherent light.
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Based on augmented ray matrix approach, a generalized model for beam-path variation induced by
spherical mirrors' radial displacements has been established. The model can be applied to analyze
beam-path variation induced by all the possible perturbation sources in various ring resonators.
Backscattering coupling coefficient r is obtained as a function of mirrors' radial displacements. Some
novel results of backscattering coupling effect have been obtained. The results indicate that radial
displacements cause bigger beam-path variation than the same value of axial displacements. r can not
be reduced to zero because of the initial machining errors of terminal surfaces of plane mirrors.
However, r can be reduced to almost zero when stabilizing frequency of laser gyro by adjusting the
radial displacements of spherical mirrors. This generalized model is useful for the cavity design, cavity
improvement, and alignment of planar ring resonators. The model is also useful for controlling the
shape of laser beams and researching backscattering coupling effect in high precision laser gyroscopes.
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The "peacock eye" phase diffractive element focuses an incident plane wave into a segment of the optical axis although
it introduces certain amount of aberration. This paper evaluates the extended depth of focus imaging performance of the
peacock eye phase diffractive element and explores some potential applications in ophthalmic optics. Two designs of the
element are analyzed: a single peacock eye, which produces one focal segment along the axis, and a double peacock eye,
which is a spatially multiplexed element, that produces two focal segments with partial overlapping along the axis. The
performances of the peacock eye-based elements are compared with the performance of a multifocal lens in the image
space through numerical simulations as well as optical experiments. In all the cases considered, we obtain the point
spread function and the image of an extended object. The results are presented and discussed.
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Theoretical and experimental analysis have shown that magnetic field has unavoidable effect on the performances of
ring laser gyroscopes. This kind of effect has been called the magnetic bias of ring laser gyroscopes in this article. The
affection of the mirror's phase shift on the magnetic bias in square ring resonators has been analyzed in this article. The
following parameters which have influence on the magnetic bias such as Ar, B, g and Rsp are taken into account, where
Ar is the distortion angle, B is the magnetic field, g is the phase shift of the mirror and Rsp is the difference of the
reflectivity for 's' and 'p' type polarizations of light. The affection of parameters gi (i=1, 2, 3, 4) on magnetic bias is
analyzed in detail, where gi are the phase shifts of four mirrors respectively. When g1=g2=g3=g4 and gi is near zero, the
magnetic bias will become very samll. When g1=g2=g3=g4 and gi is near π, the magnetic bias will become great. In
practice, g1≠g2≠g3≠g4, but, when g1+g2+g3+g4=0, the magnetic bias will become small. Especially, when g1+g2+g3+g4=0
and g1+g2=0, the magnetic bias is very small and can be ignored. In addition, when gi is near π and g1+g2+g3+g4=4π, the
magnetic bias is small. Especially, when gi is near π, g1+g2+g3+g4=4π and g1+g2 =2π, the magnetic bias is very small and
can be ignored. Based on these novel results, the magnetic bias can be eliminated by controlling the phase shifts of four
mirrors accurately in film coating process. The research on the magnetic bias of ring resonators is very important for
improving the performance of ring laser gyroscopes. These findings are important to the research on high precision and
super high precision ring laser gyroscopes.
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In this work a set of simplified theories for predicting diffraction efficiencies of diffraction phase and triangular gratings
are considered. The simplified theories applied are the scalar diffraction and the effective medium theories. These
theories are used in a wide range of the value Λ/λ and for different angles of incidence. However, when 1 ≤ Λ/λ ≤ 10, the
behaviour of the diffraction light is difficult to understand intuitively and the simplified theories are not accurate. The
accuracy of these formalisms is compared with both rigorous coupled wave theory and the finite-difference time domain
method. Regarding the RCWT, the influence of the number of harmonics considered in the Fourier basis in the accuracy
of the model is analyzed for different surface-relief gratings. In all cases the FDTD method is used for validating the
results of the rest of theories. The FDTD method permits to visualize the interaction between the electromagnetic fields
within the whole structure providing reliable information in real time. The drawbacks related with the spatial and time
resolution of the finite-difference methods has been avoided by means of massive parallel implementation based on
graphics processing units. Furthermore, analysis of the performance of the parallel method is shown obtaining a severe
improvement respect to the classical version of the FDTD method.
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Typically 4-f systems are considered as the basis for holographic memory setups. However, other geometries, such as the
convergent correlator, may also be considered. This is a setup widely used in optical processing architectures but not so
much explored in holographic data storage systems. It provides some benefits when used in optical processing such as
flexibility in the adjustment between Fourier filter dimensions and the Fourier transform of the scene. It also allows a
wider freedom in the choice of the optical systems (lenses) used in the setup since it is no longer necessary that their
focal lengths match, and the total length of the setup may be shortened. In this paper we make use of Fourier optics
techniques to analyze the validity and possible benefits of this setup in its application to holographic memories. We
consider the recording and the reconstruction steps. Both analytical expressions and simulated results are given.
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Holographic reflection gratings were stored in a PVA/AA based photopolymer material using symmetrical geometry.
Diffraction efficiency of the gratings was measured and a curing process was applied in the gratings to fix them. The
aim of this paper is to analyze the stability of stored gratings with over time, after to apply the curing process,
comparing the results obtained with and without curing.
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A holographic optical element (HOE) simultaneously accompanied with light guiding and beam shaping
function is implemented with edge-lit holograms in this study. This holographic optical element is generated
in a polymer-dispersed- liquid-crystal (PDLC) film with 20μm thickness. In the holographic reconstruction
process of the HOE, the wavefronts emitted from the light source will propagate to the HOE and a quasi
collimation diffraction beam can be obtained from this device. We demonstrate two applications of edge-lit
HOE in this study. One demonstration is a head-mounted display (HMD) system, and the other is an
illumination device for display holograms.
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Several studies of the time varying photon absorption effects, which occur during the photo-initiation process in
photopolymer materials, have been presented. Three primary mechanisms have been identified: (i) the dye absorption,
(ii) recovery, and (iii) bleaching. Based on an analysis of these mechanisms, the production of primary radicals can be
physically described and modelled. In free radical photo-polymerization systems, the excited dye molecules induce the
production of the primary radicals, R•, which is a key factor in determining how much monomer is polymerized. This, in
turn, is closely related to the refractive index modulation formed during holographic recording. In this article, we
overcome the complexicy of estimating the rate constant of intersystem crossing, kst, in going from the excited singlet
state dye to the excited triplet state dye, by introducing kaS and kaT into the model, which are the rate constant of photon
absorption from ground state to singlet state and triplet state respectively.
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The PEA photopolymer is composed of dipentaerythritol penta/hexa-acrylate as monomer and binder, N-vinyl
pirrolidone as crosslinker, ethyl eosin as dye and N-methyl diethanolamine as radical generator. This photopolymer is
suitable to work with dispersed liquid crystal molecules in dynamic holographic and diffractive applications. In order to
characterize these materials we have analyzed the behaviour of different compositions at zero spatial frequency limit.
This method is based on an interferometer that has been successfully applied in the phase-shift versus applied voltage
characterization of liquid-crystal displays, in addition to that it has been applied to characterize PVA/AA and
PVA/NaAO photopolymers. In PEA case there is no shrinkage since the photopolymer is coverplated. Samples have a
glass substrate as the cover plate. In our analysis we have studied the importance of the monomer, crosslinker and crystal
liquid molecules concentrations, in the phase shift produced in the layer during photopolymerization process.
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Protein Bacteriorhodopsin (bR) is one of the most promising and widely studied biomaterials for photonic applications
like optical storage, modulation devices and photosynthetic light energy transduction. In this paper, we present the
corresponding experimental results when pH-controlled modifications of bR doped polymeric films are realized in order
to apply these systems to all-optical switching processes and technologies.
In this work, the performance of wild type bR processed in polymeric films with different pH was tested in several series
of experiments by varying the pump beam (532 nm) period of ON and OFF and analyzing the amplitude contrast and
switching time of the probe beam (633 nm). The influence of pH values on contrast ratio and switching time were also
discussed and the optimal value was found by defining a new parameter called "switching speed". As a result, the
variation of pH can be used to obtain different time of response and speed of modulation. Concretely, we find that, in
function of pH, variations of a magnitude order in contrast ratio and time response can be obtained. So, at the red region
of the probe beam, high pH values produce high transmission with flat response in the contrast ratio and a magnitude
order variation in switching time. On the other hand, at medium pH values and when high intensities are used, the
switching time and contrast ratio are better. Moreover, it is demonstrated that as a function of the wavelength of the
probe beam the transmission response curve changes. Absorption response is very important and depends on relaxation
time processes of intermediate species which are function of pH values. Therefore, these results bring the possibility for
controlling the contrast ratio and the switching time in a specific way which could be useful for different applications.
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The chemical oxygen-iodine laser (COIL) is the shortest wavelength and high-power chemical laser demonstrated. To
model the complete COIL lasing interaction, a three-dimensional formulation of the fluid dynamics, species continuity
and radiation transport equations is necessary. The computational effort to calculate the flow field over the entire nozzle
bank with a grid fine enough to resolve the injection holes is so large as to preclude doing the calculation. The approach
to modeling chemical lasers then has been to reduce the complexity of the model to correspond to the available
computational capability, adding details as computing power increased. The modeling of lasing in COIL is proposed,
which is coupling with the effects induced by transverse injection of secondary gases, non-equilibrium chemical
reactions, nozzle tail flow and boundary layer. The coupled steady solutions of the fluid dynamics and optics in a COIL
complex three dimensional cavity flow field are obtained following the proposal. The modeling results show that these
effects have some influence on the lasing properties. A feasible methodology and a theoretical tool are offered to predict
the beam quality for the large scale COIL devices.
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