This PDF file contains the front matter associated with SPIE Proceedings Volume 8847, including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.

The main objective of this paper is to demonstrate the feasibility of producing operationally Nanocomposite polymeric thin films for sensor and light emitting applications using the innovative modified double pulsed laser deposition (DPLD) technique. The existing PLD vacuum chamber was modified to accommodate multiple wavelength laser beams for in-situ-double-ablation/Deposition (DPLD) of multiple targets of host and dopants. Special design was made for cooling of the target to the threshold of the polymer ablation without interrupting the continuity of the ablation process. Multilayered of nanocomposites of acrylic polymers and nanoparticles of NaYF₄:Tm³⁺ ,Yb³⁺ are fabricated using ultra-violet (UV) radiation (355 nm) ablating polymer targets and near-infra-red (near-IR) radiation (1064 nm) ablating inorganic targets. The films were characterized using the reflected high energy electron diffraction (RHEED), XRD , XRF, AFM, and FTIR absorption spectroscopy and tested as possible chemical sensors and light emitters.

Silicon photomultipliers (SiPMs) are intensely evaluated as a potential replacement of photomultiplier vacuum tubes for several applications. Essential key features are the photon detection efficiency, the dark count rate, the optical crosstalk and the scalability of the active area and the microcell pitch. In order to achieve considerable improvements of these parameters, KETEK has introduced a new manufacturing technology based on 200 mm wafers and 0.35 μ stepper lithography. Important aspects of the well-established and for many years optimized KETEK Silicon Drift Detector technology could be transferred to the SiPM process. Main items of the new technology are a narrow vertical trench around the individual microcells and an impurity getter: the first reduces the optical cross talk and the second the dark count rate by factor two, whereby the potential of this technology is still not maxed out. A further aspect of the new technology is a low parasitic RC-value device concept: The reduction of parasitic RC-values is targeted on a scalability refinement of SiPM devices which is mandatory for active areas above 10 mm². Finally the geometrical fill factor and the light entrance window of the KETEK device has been further improved for which reason a 50 μm cell pitch device with a photon detection efficiency of 60% in the blue range is presented. Beyond that the SiPM devices show an extremely low temperature coefficient of the gain. This is due to an operation at very high overvoltage along with a low temperature coefficient of the break down voltage.

Colorless sulfide glasses can be obtained by selecting appropriately the composition within the Ga₂S₃-GeS₂-CsCl pseudo-ternary glass system. The addition of electronegative chlorine ions into the sulfide glassy network results in a widening of its optical bandgap without altering its infrared transparency. Glasses transparent from the near UV (380 nm) up to the middle infrared (11.5 μm) are thus achievable. Such extended infrared transmission for a colorless glass is the widest among the known heavy metal oxide and fluoride glasses, e.g. fluoroindate glasses are transparent from 350 nm up to 8-9 μm. We present in this work our recent progress on the preparation of this chloro-sulfide glass of high optical quality. Efforts have been devoted in a first step to reduce the content of extrinsic impurities such as OH, SH and H₂O. In a second step, protective coatings have been deposited on polished glass samples to improve their chemical durability and assess their potential for practical applications. Large improvement of both optical quality, in terms of transmission spectrum flattening, and chemical durability were achieved. Finally, the high thermal stability against crystallization of this glass shows a high potential for lens molding and applications in multispectral imaging.

The development of X-ray techniques opens new opportunities for real-time in-situ study of photocathode growth process in details. The initial ultra thin Sb films during photocathode process were investigated on multiple substrates based on different applications. The real-time X-ray scattering and post-growth X-ray reflectivity and diffraction measurement were performed and analyzed. Experiment results indicate that Sb deposition performs a phase change from amorphous to crystalline, the critical thicknesses are different on B33 float glass, Si and Mo. Two methods were applied for film thickness calculation from X-ray scattering data, and they agree well with thickness monitor result. Sb films deposited on different substrates show similar final film roughnesses. The real time x-ray study indicates that the initial Sb layer deposition process on different substrate has different structure during deposition, the optimized thickness of the initial Sb layer may varies depends on the substrate. This study also paved the road for further study of the more complex alkali metal vapor diffusion process in photocathode growth.

The present research focused on the systematic study of the fabrication of gadolinium oxide (Gd₂O₃) and gadolinium oxide:europium (Gd₂O₃:Eu³⁺) thin films via the sol-gel and dip coating methods under normal laboratory conditions in a methanol solvent medium to determine if thin films of comparable quality could be produced. The thin films were synthesized via the sol-gel method by the hydrolysis of gadolinium acetylacetate in two different solvent mediums, absolute ethanol and methanol. The europium doped gadolinium oxide sol-­‐gels were prepared to have a final concentration of 0.01 M europium nitrate. Ordinary microscope glass slides (borosilicate glass or BSG) were used as the substrate. The substrates were cleaned and coated using the dip coating apparatus to prepare thin films that consisted of 5, 10, 30 and 50 layers. The cast films were annealed at 300°C and 500°C by direct insertion in a furnace operated under atmospheric conditions. The resulting film thickness and effective refractive indices were determined and compared. Finally, we present the introductory results of gadolinium oxide thin films as a waveguide.

We experimentally demonstrate and characterize an organic octagonal quasicrystal slab with a single-defect microcavity at low-index contrast. The gain medium is the conjugated-polymer, composed by two PPV derivatives, a BEHP-PPV and a MEH-PPV. By optical pumping, the lasing action is achieved at 607 nm with a FWHM of 1nm. The threshold of lasing is 9uJ/cm². The intensity of the lasing peak depends linearly on the pump energy above the threshold.

The complexity of photorefractive polymers arises from multiple contributions to the photo-induced index grating. Analysis of the time dynamics of the two-beam coupling signal is used to extract information about the charge species responsible for the grating formation. It has been shown in a commonly used photorefractive polymer at moderate applied electric fields, the primary charge carriers (holes) establish an initial grating which, however, are followed by a subsequent competing grating (electrons) that decreases the two-beam coupling efficiency. We show by upon using higher applied bias fields, gain enhancement can be achieved by eliminating the electron grating contribution and returning to hole gratings only.

The transfer matrix method is used to analyze induced reflection gratings in photorefractive iron doped lithium niobate in a self-pumped configuration. The optical field distribution and the induced refractive index distributions inside the material are computed, and the overall transmission and reflection are determined for different orientations of the c-axis. Numerical simulations are compared with experimental results.

An optical model to describe the reconstructed image of the collinear holographic data storage system is presented. The 2-D shape of the recording spot in the medium is simulated. The system structure parameters that influence the signal-to-noise ratio (SNR) of the reconstructed image are investigated in order to choose proper optical components to improve data storage density of the system. The role of the random binary phase mask (RBPM) utilized in the multilayer collinear holographic system is investigated. It is proved that the inter-layer crosstalk can be effectively suppressed by using different RBPMs. Different layers of data pages can be recorded with the SNR increased by a factor of six at least and the shift selectivity along z-axis can also be improved significantly.

We describe compact crystal electron beam accelerator-undulator, based on the fringing electric field from the holographic superlattice, recorded in photorefractive crystal. In proposed device plain sheet electron beam is focused into plain wave-guide composed of two crystals. One crystal serves as electrostatic accelerator, another crystal contain build-in E-field superlattice. The modeling shows, that proposed structure may be efficient amplifier for a seeding laser light in THz region.

We analyze evolution of laser-induced 2D periodic structures in semiconductor under the condition of optical bistability occuring. Optical bistability appears due to nonlinear dependence of semiconductor absorption coefficient on charged particles concentration because of both the Fermi energy level renormalization and the Burstein-Moss effect. The electron mobility, diffusion of electrons and laser-induced electric field are taken into account for analyzing the laser pulse propagation in the semiconductor. We found out various modes of laser-induced spatial structures developing of charged particles concentrations in dependence of optical intensity and the absorption coefficient. One of them consists in periodic appearance and moving of stable spatial electrons distribution. We discuss also the finite-difference schemes, which can be used for computer simulation of considered problem.

We have designed an all-normal dispersion photonic crystal fiber optimized for pumping at 800 nm with initial pulses which are typical for conventional Ti:Sapphire lasers. Parabolic pulse formation and supercontinuum generation in this fiber is analyzed both in time and frequency domains.

A new type of colorimeter with multiple channels was demonstrated using a side illuminated optical fiber. When different spots of a properly modified fiber are side illuminated, multiple signals are generated and guided by the waveguide: the essence of multiplexing. This configuration is simple, low cost, does not require a sensitive coating and can analyze several samples along the fiber with a single detector: the most expensive component. Since regular colorimeters use one detector per sample, our new configuration considerably lowers the cost of analyzing multiple samples. This system consists of a fiber mounted over a support, three LEDs, an LED driver, a photo diode and a read-out: to increase the signal, the fiber was tapered. For calibration purposes, six solutions of different concentrations of food dye were prepared, placed inside cuvettes along the fiber length and illuminated by the LEDs. This light passes through the solution, strikes the fiber and is guided to the detector: the darker the solution the lower the signal intensity. Several calibration curves were obtained using different light intensities: it was found that the greater the intensity, the higher the colorimeter sensitivity. This simple capability can be used to easily control the device’s sensitivity and its resolution. Although built for three samples only, this device can be modified to accommodate more. With cuvettes measuring 1 cm, it is possible to accommodate one sample per cm of fiber. Also, with minor modifications, this colorimeter can be used for fluorescence, scattering and index of refraction measurements.

We present optically pumped semiconductor disk lasers (OPSDLs) emitting in the 900–1100nm band which are frequency doubled to access the visible spectrum. In particular, we focus on presenting the design, fabrication, and specific characteristics. Fundamental outputs exceeding 20W and visible radiation with powers of 5–10W are achieved. The blue and green emission at wavelengths around 450–470 and 520–540nm yield advantageous gamuts for display applications and can be utilized for stereo projection. Moreover, other accessible wavelengths in this spectral region, e.g. 493 nm, and the good beam quality of these devices enable optical ion trapping experiments.

An approach using holographic techniques to fabricate an optical concentrator for a solar cell is described. This concentrator consists of a hologram and a lenticular lens. The lenticular lens collects the sunlights from arbitrary incident angles. The sunlights are then launched into the hologram and generate diffracted light waves. Most of the diffracted waves are normally incident into the solar cell. Thus, reflectivity of the light on the surface of the solar cell is minimized, and the solar energy concentration is increased.

By taking advantage of the recent advances in high quality sizable KTN crystal growth, a broadband large field of view (FOV) EO modulator is developed and presented in this paper. The experimental and theoretical studies indicate that the built EO modulator not only has a broad bandwidth (~1 GHz) but also has a large FOV (+/- 30 deg) because cubic phase KTN crystals do not introduce any intrinsic birefringence without applying the external electric field.

In the work, we have presented the technique based on the FDTD method for the dispersion computation of a single-mode ber with an arbitrary refractive index pro le. In contrast to other numerical methods the FDTD allows studying the beam propagation along the ber taking into account material dispersion and the nonlinearity. Particularly, we have concentrated attention on the method details that allowed us to reduce dramatically the computation time and achieve the accuracy close to the one provided by the nite elements method.

A novel approach to calibrate a phase-shift formed in a long-period fiber grating (LPG) is proposed and successfully demonstrated, which is based on the use of either a power- or a wavelength-interrogation technique to the loss-peak existed in the transmission spectrum of the phase-shifted LPG. Moreover, in this study, by tapering a LPG with CO₂ laser, phase-shift is successfully created at central part of the LPG. Finally, base on the use of this kind of phase-shifted LPG, a simultaneous measurement for the temperature and the surrounding refractive index has been proposed and experimentally demonstrated.

We propose an intra-cavity index sensor based on double cladding ytterbium-doped photonic crystal fiber filled with liquid analyte in the air holes of optical fiber cladding. In such sensor, when pumped by 976 nm light, the output power of the ytterbium-doped photonic crystal fiber laser can be influenced by the refraction index of liquid analyte to achieve the intra-cavity fiber sensing. The numerical analysis shows that the power change is larger in a small range of loss when the end reflectivity is higher, and the sensor’s sensitivity will be higher for the change of refractive index of analyte.

Novel method is proposed for determination of nonlinear-optical crystal both heat transfer and optical absorption coefficients by measuring kinetics of the laser-irradiated crystal temperature-dependent piezoelectric resonance frequency. When laser radiation propagates through the crystal its temperature evaluation with time is directly determined from crystal piezoelectric resonance frequency shift, which is precisely measured by analyzing crystal response to the applied ac electric voltage. Heat transfer and optical absorption coefficients are obtained using measured characteristic time of crystal laser heating kinetics by solving nonstationary heat conduction equation. Experiments were performed with nonlinear-optical α-quartz, lithium triborate (LBO) and periodically poled lithium niobate (PPLN) crystals.

Advances in SPAD arrays propose improving the fill factor by confining several SPADs in the same well, with a main issue related to crosstalk. For measurements triggered only in well-defined time periods that can be known in advance, the pixels can be inhibited before the arrival of the crosstalk charge. This paper reports the crosstalk characterization of in an array of SPADs fabricated in a conventional CMOS technology in the same n-well (fill factor 67%). A long gating time gives a crosstalk not less than 2.75%, while reducing it below 2.5 ns completely eliminates crosstalk, as predicted by the theory and by TCAD simulations.

In this paper, the fabrication of nanostructures on curved surfaces is presented, which includes following procedures: First, a three-dimensional nanostructured mold with curved surfaces is created by ultrafast femtosecond laser ablation. Second, nanostructures on the curved surface are created via soft nanoimprint. Furthermore, the performance of antireflection coating (ARC) based on the nanostructures created on the curved surface is quantitatively evaluated. The simulation and experimental results show that a very high quality ARC (i.e., <99% transmission within the entire visible spectral range and over a broad field of view 120 deg) can be realized by using the proposed nanostructures. In particular, the large FOV makes it particularly suitable for applying the ARC on the curved surface, which can be greatly beneficial for a variety of applications such as ARC for lenses and curved windows.

A novel torsion sensor based on a Mach-Zehnder interferometer is presented. The interferometer is made with a piece of Ytterbium doped photonic crystal fiber (YbDPCF) spliced between two single-mode fibers. The torsion sensitivity obtained is 0.05nm/º in a torsion range from 0° to 360° along with a sensitivity of 0.06dBm/º at specific wavelength. The interference fringes and torsion characteristics have been experimentally investigated and demonstrated. This compact fiber component with acceptable sensing performance makes its a good candidate for the measurement of numerous physical parameters.

Photonic crystals (PhCs) have emerged as one of the most significant topics in the field of optical communication since their first introduction by Yablonvitch 1 and John 2. Recently, interest has been grown in the design and development of optical logic gates based on different schemes ^3-10. In this paper, we report the design of optical logic AND gate based on two structures, one of which is a hexagonal lattice with silicon (Si) rods in air (SRA) and another is the hexagonal lattice arrangement of air holes in silicon (AHS) with air waveguides. Both the gate structures are based on Y shaped PhC waveguides and analyzed by plane wave expansion (PWE) method. The simulation results show that the proposed structures operates as an AND gates and has a bit rate of 2.016Tbit/s for SRA and 1.785Tbit/s for AHS structure. By appropriately choosing the size and the interaction length of the central rod in SRA and size of central hole in AHS, the optimal performance of the proposed AND logic gates has been achieved.

To enhance the channel impulse response and signal quality through a multimode fiber, the incident wavefront into a multimode fiber may be controlled using phase masks, gratings and spatial light modulators. In this paper, an elegant technique for controlled coupling into a multimode fiber is demonstrated using a solid-core photonic crystal fiber to reduce differential mode delay in a multimode fiber. The increase in the number of tiers of a solid-core photonic crystal fiber is shown to reduce differential mode delay and improve the bit-error rate of a multimode fiber channel.

An integrated photoconductive (PC) sensor is introduced as an optoelectronic element for visible light optical wireless communications (OWC) links. The sensor applies the standard PC switch, being a biased metal-semiconductor-metal gap, in a three-fold-symmetric corner-cube architecture with a summed output photocurrent at the vertex. Such a form facilitates bidirectional retroreflective communications to meet fundamental OWC requirements for broad directional and broad spectral capabilities. The ultimate OWC capability, for ultrafast optoelectronic switching times, is studied here for material response and transit time response, and it is shown that ultrafast (picosecond) optoelectronic switching times can be achieved and the general device design consideration is discussed for emerging visible light OWC systems.

Novel method of piezoelectric resonance spectroscopy is introduced for nonlinear-optical crystals equivalent temperature measurement during frequency conversion of laser radiation. Equivalent temperature of the crystal heated by laser radiation is directly determined from its strongly temperature sensitive piezoelectric resonance frequencies. Method was applied for PPLN crystal temperature measurement during second harmonic generation of CW ytterbium fiber laser radiation. Temperature tuning curves of PPLN and its phase matching temperature dependence on pump power were precisely measured using concept of the equivalent temperature. Hysteresis of PPLN temperature and optical bistability of second harmonic power in respect to pump power were observed.

We propose a compact, high efficient full photonic crystal Mach-Zehnder interferometer based on the self-collimation and photonic band gap in a Rod-type Photonic Crystal. Line defected photonic crystals are used as the beam splitter and the mirror. Self-collimation frequency range is confirmed by employing the plane wave expansion method. The interference is investigated with the finite difference time domain simulation technique, and the simulation results agree well with the theoretical prediction. Because of their small dimensions, the proposed MZ interferometer hold great potentials for applications in photonic integrated circuits.

Focusing on the graded negative index lens made by annular photonic crystals (APCs) are theoretically studied. The graded annular photonic crystal (GAPC) is composed of a dielectric-rod and a circular-air-hole array in a triangular lattice. The grade index is achieved by gradual modification of the radius of the rod along the transverse direction to propagation. The properties of the GAPC are analyzed by using the Plane Wave Expansion (PWE) method and numerical simulation is studied by using the Finite-Difference Time-Domain (FDTD) method. The results show that the GAPC can realize the focus of plane waves and the focal length can be designed with the wave frequency.

Optimization of high fixed diffraction efficiency in LiNbO₃:Ce:Cu is investigated. Holographic gratings are recorded using typical recording wavelengths including 488, 514 and 633 nm in LiNbO₃:Ce:Cu for different doped concentration. Optimal switching from recording step to fixing step is taken into consideration. The experiment results can confirm the optimal recording wavelength and doped concentration for high fixed diffraction efficiency in LiNbO₃:Ce:Cu crystal by optimal switching from holographic recording to fixing.

Laser beam scanners are important optical elements with a large variety of applications in the measurement techniques, optical communications, laser imaging ladar, etc. Agile beam steering of optical radiation using phased arrays offers significant advantages, such as weight, stability and power requirements over conventional beam steering systems. There are several kinds of optical phased array technology to be developed, such as Lithium tantalite phase shifters, lithium niobate electro-optic prism deflectors, and liquid crystal and ferroelectric liquid crystal phase modulations. However, one of the major drawbacks of these approaches is low light efficiencies because of the side lobes in far-field pattern of the steering beam. In this paper, a new low side lobe optical beam steering technique using phase correction technique is proposed. A stable and fast single-lobed far-field pattern in steering beam can be obtained from the optical phased array with a phase plate by optima design. It can result in a substantially increased light efficiency and beam quality. The quantitative calculation results of typical optical phased array are demonstrated. The low side lobe optical beam steering technology of optical phased array will benefit many practical applications such as laser ladar, laser communications and high resolution displays.

Volume gratings are of wide interest in many applications because of their properties of high diffraction efficiency, excellent wavelength selectivity and angular selectivity. Ultrashort pulsed laser has many promising applications in the fields such as optical communication, signal and imaging processing. Because of its abundant spectrum and wide bandwidth, the diffraction properties of volume gratings under illumination by ultrashort optical pulse will be different from that of a monochromatic continuous wave. A periodical structure is highly dispersive and such a dispersive property can be used to control the group velocity of light beams. So the spectral properties and dispersive properties of the periodically layered structures such as volume gratings when a linear chirped Gaussian pulse illuminated are very necessary. These properties can be applicable to addressable filter, switching, and controllable optical delay line. In this paper, a detailed study of linear chirped ultrashort pulsed beams diffracted by volume gratings in dispersive media is performed. The group delay characteristics of the diffraction spectrum of the transmitted and reflected volume gratings were studied based on the modified coupled wave theory. The analysis and observation of this paper will be valuable for the designing optical elements based on diffractive structure for the use with linear chirped ultra-short pulsed waves.

In this paper, we report on how electrochromic coloration is affected by oxygen deficient stoichiometries in amorphous tungsten oxide (a-WO_x) films prepared by a dc reactive magnetron sputtering. The peak color efficient (CE) value of oxygen partial pressure at the optimum 6.5×10^-3 Torr is improved about nine-fold larger than that of 2.0×10-3 Torr even in the nearly stoichiometric a-WO_x films. We attributed that the optical absorption of a colored a-WOx film can be satisfactorily described by an intervalence charge-transfer transition (ICTT) mechanism between localized W⁵⁺ and W⁶⁺ states. Therefore, we have determined the most suitable condition (by increasing the partial oxygen pressure) to produce a-WO_x films, thus offering a good electrochromic performance for opto-switching applications.

One-color photorefractive holography has been investigated in the oxidized LiNbO₃:Fe:Ru crystal with recording wavelength 632.8nm. The crystal shows a high asymmetric behavior in grating buildup and readout erasure rates. This remarkable property shows that the recorded grating is quasi-nonvolatile during readout. In this paper, the effect of the pre-sensitizing process and the readout intensity on the asymmetric behavior is investigated experimentally, the results show that the recording sensitivity can be increased by the pre-sensitizing process, and the grating lifetime can be extended by increasing readout light. At last, the reason for the high asymmetry is explained qualitatively in terms of a multiple center model.

Photonic crystal (PhC) waveguides are the prospective structures for high-speed optical micro-devices. Possessing high-effective light localization, such waveguides allow introducing active materials making additional all-optical signal control possible. The most effective from the technological point of view is embedding the PhC filters with characteristics close to the ones of the background PhC (i.e. with the same refractive index, PhC period, etc.). As has been shown in previous papers,^{1, 2} such filters possess spectral characteristics that allow using them for processing the ultra-short pulses in case of either passive (implemented with linear materials) of active (with nonlinear materials) devices. Moreover, from the technological point of view such PhC waveguides with filters can be easily integrated into the electronic circuit which reduces costs and production time.

Unfortunately, optical losses and back reflection from such a filters makes them unsuitable for high-speed integrated optical circuits.

In this work we propose analysing both density of modes (DOM) and the transmission spectra to optimize the parameters of the PhC filters made of linear or nonlinear material.

Proposed characteristics have been first introduced to optimize the PhC filters used for wavelength division demultiplexing.³ However, since waveguiding properties have not been taken into account, the photonic density of states maps as well as transmittance maps can be applied with high accuracy to a bulk PhC but not to confined PhC filter. Taking into account waveguiding properties provides great enhancement to the precision of characterization of the confined PhC filters.

The formation dynamics of crossed-beam photorefractive gratings formed by the in Fe doped LiNbO₃ crystal is studied based on jointly solving the material equations and the two-dimensional coupled-wave theory. The numerical calculations of the temporal and the spatial evolutions of the space-charge field and the light modulation depth are given, and the influence of the recording conditions, including the recording wavelength, the two-dimensional sizes of the holographic grating are presented, and the time evolution of diffraction efficiency during holographic recording is also presented.

A side illuminated optical fiber sensor with three sensing points and an absorption-based indicator in the cladding was demonstrated for the first time. This device is easy to manufacture, uses leaky modes as the signal carrier and can measure RH in air, soil, concrete and other environments. So far, only side illuminated fluorescence sensors have been reported. They were thought, erroneously, to have their entire signal generated by evanescent wave coupling when, in fact, leaky modes also play an important role. This, coupled to the prevailing misconception that leaky modes propagate for very short lengths of fiber, prevented the earlier discovery of this absorption-based configuration. A 25 cm long fiber, with a cladding doped with an absorption dye sensitive to Relative Humidity (RH), was used in this demonstration. The fiber was side illuminated by a broadband LED, a fraction of this light was absorbed by the cladding and the remaining light guided to the fiber tip as low loss leaky modes. A total of three sensors, two with three sensing points and one with two, were calibrated using a low cost photometer. The signal was linear, stable, increased with RH and had resolutions between 0.11% and 0.25% in RH. With 5 mm diameter LEDs, devices with at least two sensing points per centimeter of fiber can be easily fabricated resulting in sensors with a very high density of sensing points. Compared to the prevailing axial illumination approach, the side illuminated sensor was found to be far simpler and inexpensive.

A new design and fabrication of flat optical lens by use of 90-degree volume holographic grating recording geometry is presented. It is recorded by the interference of a plane wave and a spherical wave in a Fe-doped LiNbO₃. The flat optical lens can laterally transfer and focus the plane wave which perpendicularly incidents on the planar crystal surface. The optimal switching from recording to thermal fixing is taken into consideration in order to obtain the nonvolatile hologram with maximum fixing efficiency. The flat optical lens with different recording and reconstructing wavelength has also been discussed. The flat optical lens has the advantages of light weight, laterally transferring and focusing, small duty ratio, and easy for the microstructure integration. The testing results measured verify that the flat optical lens can successfully be used for the free space optical communication.

We suggest combining several optical methods of remote sensing and characterization of crude oil films and emulsions: coherent fringe projection illumination (CFP), holographic in-line interferometry (HILI). Combined methods of CFP and HILI are described in the frame of coherent superposition of partial interference patterns. Moreover, we evaluated different alternative schemes of interferometry with holographic recording and preliminary holographic amplification in photorefractive crystals. Holographic amplification of weak images without phase distortions is possible in a special mode of holographic recording in photorefractive crystals.

A scanning approach using holographic techniques to perform the 3D shape measurement for a non-diffusive object is proposed. Even though the depth discontinuity on the inspected surface is pretty high, the proposed method can retrieve the 3D shape precisely.

In this paper, we present a scanning approach to retrieve the 3D shape of the object with large depth discontinuities. A fringe pattern is projected onto the inspected object. A CCD camera is used to observe the projected fringes. The depth-of- field of the camera lens is so short that only fringes within the focused area can be clearly observed. By moving the inspected object around the focused area along the depth direction, a set of images, which addresses the contour of the object with its corresponding depth, is obtained. The 3D shape of the object is then retrieved by assembling the image contours with their corresponding depths.

The plasmon-active mixed gratings were demonstrated and characterized in a volume holographic polymer nanocomposite. The counter-diffusion physical mechanism between the polymeric component and nanoparticles related to the holographic mixed gratings was analyzed. By dispersing gold nanoparticles in the bulk holographic polymer, a plasmon-active strong absorption grating was introduced into the polymeric refractive-index gratings. The nanocomposites with several volume ratios of doped gold nanoparticles were fabricated. Holographic angular selectivity curves of saturated diffraction efficiencies were measured for the prepared samples. Significantly suppression of side lobes with the improved diffraction efficiency was observed in the gold nanoparticles doped photopolymer. It is found that the noticeable holographic-apodization phenomenon is caused by the plasmon-active strong absorption grating.

In our continuing effort of developing electromagnetic-electromechanical-electrooptic interactive devices, the effect of piezoelectric resonance on the performance of electrooptic modulators is investigated. Time domain finite element models were constructed to determine the phase shift due to the induced birefringence of the device. Two sinusoidal voltage sources are used one to sweep over a range of frequencies while the other setting the modulator at a selected resonance frequency. Ferroelectric single crystals such as LiNbO₃ and Pb(Zn_1/3Nb_2/3)O₃-PbTiO₃, were examined for their induced index of refraction, the induced phase shift, and the half-wave voltage of given configurations. The time domain model of dual signal ac biased configuration displayed wide bandwidth enhancement when biased at proper resonant modes, which matches well with experimental observations. The results demonstrate the piezoresonant enhancement in terms of low half wave voltage and high electrooptic coefficients in broad frequency ranges. The results also provided corresponding insights that further our understanding on experimental observations reported previously by the authors. The models are suitable for designing of electrooptic device configurations that optimize the properties desired.

Self phase modulation is a nonlinear effect that is observed when a laser beam is focused on to a high-absorbing thermal medium. A regular tea sample in a plastic cuvette is used as the nonlinear absorbing sample. The change in the refractive index of the medium occurs due to the heat generated by the focused pump beam, which in turn changes the refractive index. In this paper, self phase modulation is investigated in different ways. An Ar-Ion laser of 514 nm is used as the pump beam and a 632 nm He-Ne laser is used as the probe beam. The probe beam is introduced from the opposite side of the pump beam. Ring patterns are observed from the each side of the sample. Regular far field ring patterns are observed from the pump beam, and two sets of rings are observed with the probe beam. The behaviors of these inner and outer rings are monitored for different pump powers. The steady state heat equation is solved to obtain an exact solution for the radial heat distribution and far field ring patterns are simulated using the Fresnel–Kirchhoff diffraction integral. Ring patterns are theoretically explained using simulations results, and compared with experimental observations. Finally, an interferometric setup using the low power He-Ne laser is also used to determine the induced change in refractive index. Results are compared with those obtained directly from self-phase modulation and from the probe beam method.

We present a multi-trench channel waveguide design that supports a single-guided mode with large-mode area. Geometrically shaped waveguide with suitable design parameters ensure effective single-mode operation by introducing high leakage loss to higher-order modes while a nominal loss to the fundamental mode. A waveguide of ~ 2.2 mm length is able to ensure single-mode operation with the core area of 100 μm². Such a large confinement area for mode propagation can effectively suppress nonlinear optical effects. The proposed channel waveguide structure is expected to find applications in high power devices and components such as high power waveguide lasers, amplifiers and sensors.

A large-mode-area (LMA) single-mode (SM) photonic crystal fiber (PCF) structure for applications in high power fiber lasers, amplifiers and sensors is proposed. In the proposed structure the center air hole has been removed to form the core and the six elliptical air holes of inner ring around the center core have been selectively filled with high refractive index material. Effects of design parameters on SM operation and mode area are numerically investigated by using the full vectorial finite-element method. Structure offers large-mode-area exceeding 835 μm² at 1.064 μm wavelength. A PCF with such a large-mode-area would significantly reduce the nonlinear effects and would be useful for high power applications.

We report the preparation and investigation of ferroelectric field effect transistors (FET) using ZnO:Li films with high field mobility of the charge carriers as a FET channel and as a ferroelectric active element simultaneously. The possibility for using of ferroelectric FET based on the ZnO:Li films in the ZnO:Li/LaB₆ heterostructure as a bi-stable memory element for information recording is shown. The proposed ferroelectric memory structure does not manifest a fatigue after multiple readout of once recorded information.

The peculiarities of charge carrier transfer mechanism in ZnO films doped by donor or acceptor impurity and metal−dielectric electronic phase transition were investigated. The control parameter of this transition is concentration of interstitial Zn atoms. The films with high concentration of interstitial Zn atoms have high conductivity of metallic type. Air annealing leads to change of conductivity temperature dependence from metallic type to dielectric one.

In this paper we present the tomographic studies of refractive index distribution in polymer bridges between two optical fibers. Detailed refractive index maps are needed in order to improve the technological process of manufacturing of those bridges and to achieve lower return losses. At first the technological process of bridges fabrication through photopolymerization is presented. The interferometric measurements of reference fibers used to produce those bridges and two series of microbridges are performed in visible (632.8 nm) and infrared (1550 nm) experimental systems. The relations between vis and IR results are determined, which allows for performing tomographic measurements in more accurate conditions secured in visible spectrum. The experimentally obtained refractive index distributions in microbridges are used for modeling the insertion and return losses, which are compared with the real losses obtained for the produced microbridges. This knowledge will be used for better understanding of the manufacturing process and its further optimization.

Acousto-optic device are used in various signal processing systems and laser radiation controlling systems. These systems allow the wideband signals processing in real-time and high-speed laser beam scanning. In this paper, dependences of electromechanical coupling coefficient for different slices of a lithium niobate crystals are calculated. They illustrate the validity of selecting the appropriate cut for the piezoelectric transducer for the excitation of longitudinal waves and shear waves in acousto-optic cells. Also, these dependences determine the criteria for the accuracy of the technological requirements for the piezoelectric plate transducers constructing.