We propose a photonic crystal dual-resonant microcavity and waveguide-coupled temperature sensor structure. The resonant characteristics of photonic crystal microcavities are simulated by finite-difference time-domain method. Due to the positive thermo-optic effect of silicon and the negative thermo-optic effect of SU-8 photoresist, a resonant wavelength shift is detected for temperature sensing in the opposite direction, which significantly improves the sensitivity of the sensor. Simulation results highlight that the sensitivity of the temperature sensor is 124.69 pm / ° C, the temperature measuring range is ∼150 ° C, and the limitation of the temperature sensing area is reduced. The sensor can be integrated to lab-on-chip and system-on-chip to achieve real-time temperature measurement in different microregions.
Wavefront coding (WFC) is a hybrid technology designed to increase depth of field of conventional optics. The goal of our research is to apply this technology to the short-focus and ultra-wide-angle lens which suffers from the aberration related with large field of view (FOV) such as coma and astigmatism. WFC can also be used to compensate for other aberration which is sensitive to the FOV. Ultra-wide-angle lens has a little depth of focus because it has small F number and short-focus. We design a hybrid lens combing WFC with the ultra-wide-angle lens. The full FOV and relative aperture of the final design are up to170° and 1/1.8 respectively. The focal length is 2 mm. We adopt the cubic phase mask (CPM) in the design. The conventional design will have a wide variation of the point spread function (PSF) across the FOV and it is very sensitive with the variation of the FOV. The new design we obtain the PSF is nearly invariant over the whole FOV. But the result of the design also shows the little difference between the horizontal and vertical length of the PSF. We analyze that the CPM is non-symmetric phase mask and the FOV is so large, which will generate variation in the final image quality. For that reason, we apply a new method to avoid that happened. We try to make the rays incident on the CPM with small angle and decrease the deformation of the PSF. The experimental result shows the new method to optimize the CPM is fit for the ultra-wide-angle lens. The research above will be a helpful instruction to design the ultra-wide-angle lens with WFC.
It is difficult to process quartz to get a large aperture ratio micropore(Φ127μm) by the mechanical tools, but it is possible processed by MEMS technology. The fluorine etching technology is used in experiments. The etching rate of quartz is proportional to the concentration of the HF acid. The etching rate of the mixtures of different proportions of the HF acid (49%) and the NH4F solution (35%) can be acquired, and the etching rate is lower if NH4F solution (35%) replace by the saturated NH4F solution. The experimental results conform to the chemical equation of Judge J S. In the experiment of the micropore etch, the wafers are respectively put in the mixtures of 1:1 and 3:2 ratio of the hydrofluoric acid (49%) and the ammonium fluoride solution (40%), and the morphology of micropore can be observed by the scanning electron microscopy and the confocal microscopy, and then the deepest depth of the micropore is tested by the confocal microscopy, the relationship between etching rate and the proportional of mixed solution can be got.
Photoacoustic imaging is a potential medical imaging technique to reconstruct and image the inside structure of tissue.
The principle of pulsed optoacoustic signal generation and the comparison between the traditional piezoelectric detectors
and optical detectors are described. Through analyzing the principle of sensing film, we find that in a rigid-back sensing
film the relation between pressure amplitude (PO) and thickness amplitude (dl0) is P0= E/2ldl0. In order to realize a
whole field, non-touch, high precision and backward-mode photoacoustic detecting, a new kind of sensing film detector
based on Fabry-Perot sensing head is proposed. For the especial configuration of dichroic mirror, the detector not only
enables photoacoustic excitation laser pulses to transmite through the sensor, but also enables the laser speckle formed
on the interface to reflect into the CCD. Bying using this detector we design a photoacoustic imaging system based on
the outside displacement Digital Speckle Pattern Interferometry (DSPI) detecting system. To reduce the cost of system a
standard CCD whose exposure time is about tens of milliseconds is adopted as light detector. By interrogating the sensor
with a short laser pulse with about tens ns bandwidth, we resolve the problem of match between the CCD and acoustic
field at MHz frequency. In principle, the reconstruction algorithm based on the decomposition can be applied to
reconstruct a three-dimensional photoacoustic image The technique will offer a method with a whole field,
backward-mode, 3D and all-optical detecting for high-resolution biomedical imaging.
Photoacoustic imaging is attracting increasing interests in biomedical imaging. The comparing between the traditional
piezoelectric detections and optical detections is described. Three kinds of all-optical detection photoacoustic imaging
systems, including system based on optical reflectance at a glass-liquid interface, system based on FP polymer film and
the system based on POISe, are introduced and compared in this paper. Because these methods are difficult to realize
measuring the photoacoustic signal on a 2D plane with the backward detection mode, a new kind of photoacoustic
imaging system based on Electronic Speckle Pattern Interferometry (ESPI) is proposed. An ESPI outside displacement
measurement system is adopted to detect the surface displacement of sample. Since the exposure time of a standard CCD
which is of the order of tens of milliseconds, the temporal resolution to sample an acoustic field at MHz frequencies is
achieved by interrogating the sensor with a short laser pulse whose bandwidth is about 20ns. After measuring and
disposing the displacement data of the sample at a series detecting time, the photoacoustic image will be reconstructed
by a delay and sum beam-forming algorithm or by a reconstruction algorithm based on the decomposition. In principle,
the system will realize noncontact and backward-mode inspection and smaller element sizes of the receiver in the
photoacoustic imaging application.
A novel automatically measuring planning method in coordinate metrology based on computer vision is presented in this
paper. An active stereo vision system is established by attaching a CCD camera to the mechanical probe of the
coordinate measuring machine (CMM). Through the movement of the probe of the CMM, as well as the camera, 3D
edge characters of the object can be acquired, which are used as clues for automatically coordinate measuring. A multi-baseline
matching method is presented to overcome the ambiguity in stereo matching, and a quadratic interpolating is
used in sub pixel matching to get continuous depth image. The matching is only done on character edges in images, so it
is much faster and more robust. Two methods of measuring path planning are put forward, in one way, a 2D
characteristic edge image which are often stand for rapidly changes in depth or curvature of object surface can be
acquired by projecting 3D edge characters to a scanning plane, and then the sampling points of mechanical probe are
selected depending on the edge image. In the other way, surface patches are fitted to these 3D edges, and the sampling
grid is determined by the type and area of every patch. Using these techniques, a highly automated high-speed, high-precision,
3-D coordinate acquisition system based on multiple-sensor integration can be developed. It has potential
applications in manufacturing problems as metrology, inspection, and reverse engineering.
The shape and energy distribution of laser beam directly define its applications in laser processing. In order to cater for
different laser processing requirements, the input beam always needs to be transformed. The transformation between the
solid beam and ring beam can be realized by the axicon-based optical devices. A beam transformation optical system,
which uses a pair of positive axicon and negative axicon is designed and analyzed. The novelty of the optical system is
not only that they can focus the laser beam on a ring pattern or solid beam pattern, but also that they can change the
diameter of patter easily by adjusting the separation of the two conical lenses. The optical system is analyzed based on
the geometry optical theory. By adjusting the separation of the convergent conical lens and the divergent conical lens,
different shapes and the energy distributions are gained. At last, a measurement method of the beam profile is introduced
which based on charge coupled device (CCD) The results show that the axicon-based beam transformations raise the
effectiveness of laser and have a wide application prospect in laser processing field.
A novel scheme is proposed to achieve all-optical SPM-based wavelength conversion in a bismuth oxide-based highly
nonlinear photonic crystal fiber. It consists of erbium-doped fiber amplifier, optical circulator, Fiber Fabry-Perot filters,
photonic crystal fiber and fiber Bragg grating. Owing to SPM, a recirculating configuration is designed to induce the
further spectral broadening and wavelength conversion is achieved with a tunable Fiber Fabry-Perot filter. The
simulation results of bismuth oxide-based photonic crystal fiber indicate that the effective index of the fundamental
mode increases monotonically with the increase in the hole pitch, or the decrease in the ratio of the hole diameter to the
hole pitch. The mode effective area steadily increases with the hole pitch. The nonlinear coefficient, which is beneficial
to shorten the fiber length and reduce the required optical power, is expected to be 1100W-1km-1 by using bismuth
oxide-based glass with high nonlinear refractive index and reducing the effective core area with holey microstructure.
The mode-field diameter of bismuth oxide-based is estimated to be 1.98μm and the predicted small effective core area is
3.3μm2. The propagation loss at 1550nm is about 0.8dB/m. The obtained results show that SPM-based PCF-WC has a
potential of wide conversion bandwidth, high response time, simple configuration and low insertion loss etc.
All-optical wavelength conversion plays a major role in providing the wavelength flexibility in optical communication networks. All-optical wavelength converters (AOWCs) based on cross-gain modulation (XGM) and cross-phase modulation (XPM) in semiconductor optical amplifiers (SOAs) have attracted considerable research interest. In this paper, we propose a novel scheme for cascaded wavelength conversion based on cross-gain modulation and cross-phase modulation in SOAs. The wavelength conversion operation in the proposed scheme includes two stages, that is, XGM in the first stage followed by the stage of XPM, and thus is expected to have a high ER and a large input power dynamic range simultaneously.
A simple architecture of all-optical wavelength conversion in a highly nonlinear bismuth oxide-based photonic crystal
fiber (PCF) is proposed, which consists of an erbium-doped fiber amplifier, a polarization controller, a nonlinear medium
PCF, two tunable fiber Fabry-Perot filters and an optical isolator. Self-phase modulation is utilized to induce spectral
broadening for all-optical wavelength conversion. The desired dispersion properties can be tailored by the parameters of
bismuth oxide-based PCF microstructure. The propagation loss at 1550nm is about 0.8dB/m. The nonlinear coefficient is
expected to be 1100W-1km-1 by using bismuth oxide-based glass and reducing the effective core area. The mode-field
diameter of PCF is estimated to be 1.98μm and the predicted effective core area is 3.3μm2. The intermediate high
numerical aperture fibers between bismuth oxide-based PCF and single-mode fibers are considered to reduce the splicing
loss. The obtained results show that the all-optical wavelength converter has a potential of high conversion efficiency,
wide conversion bandwidth, ultrafast response time, compact configuration and low insertion loss etc.
A novel architecture of all-optical wavelength conversion in a highly nonlinear bismuth oxide-based photonic crystal
fiber (PCF) is demonstrated. Self-phase modulation is utilized to induce spectral broadening for the all-optical
wavelength converter. A recirculating configuration is designed to obtain the twice spectral broadening. Therefore,
wavelength conversion is achieved. The design and the simulation of PCF are demonstrated. The desired dispersion
properties can be tailored by the parameters of bismuth oxide (Bi2O3) PCF microstructure. The propagation loss at
1550nm is about 0.8dB/m. The simulation results of PCF indicate the relationship of the effective index of the
fundamental mode, the mode effective area and the holes pitch of PCF. The nonlinear coefficient is expected to be
1100W-1km-1 by using bismuth oxide-based glass and reducing the effective core area. The mode-field diameter of PCF
is estimated to be 1.98μm and the predicted small effective core area is 3.3μm2. The design of Bi2O3-based PCF and the
intermediate high numerical aperture fibers between Bi2O3-based PCF and single-mode fibers are considered to reduce
the splicing loss. The obtained results show that the wavelength converter has a potential of wide conversion bandwidth,
high response time, simple configuration and low insertion loss etc.
KEYWORDS: Waveguides, Signal processing, Wavelength division multiplexing, Modulation, Optical amplifiers, Switching, Signal detection, Signal attenuation, Data conversion, L band
In this paper, we proposed a variable operation of a DC-OFS based on double SFG+DFG (Double-SFG+DFG-OFS)
nonlinearity process for the first time. We studied the principle and configuration of three DC-OFS in detail both
theoretically and experimentally. In order to compare with Double-DFG-OFS and Double-SHG+DFG-OFS, we also
used two four-channel-controlling multiple-quasi-phase-matched LiNbO3 wavelength converters and got ten different
outputs spreading across a wavelength range of as broad as 35 nm by changing the combination of two controlling
wavelengths of the two wavelength converters. And one channel signal was converted to shorter and longer wavelength
and the same wavelength by changing the controlling wavelengths. We got higher conversion efficiency compared with
the other two DC-OFSs mentioned above. We used novel M-QPM-LN wavelength converters having a continuously-phase-
modulated domain structure, which can be operated by multiple pump wavelengths with minimum loss of
efficiency. The periods were 14.8μm. The phase of the periodic poling was continuously modulated to satisfy the QPM
condition at four different wavelengths. The frequency spacing of control signal-b is twice as large as the control signal-a.
The operating temperatures were 102.5 and 100.5 C for the first and the second QPM-LN wavelength converters,
respectively.
All-optical wavelength converters (AOWCs) are considered to be important components in future wavelength-division-multiplexed
(WDM) networks. Cross gain modulation schemes in semiconductor optical amplifiers (SOA) are promising
candidates for an all-optical wavelength conversion application due to the simple implementation and effective
conversion. However, the slow gain recovery time of SOA limits the maximum operation speed and causes unwanted
pattern effects. This paper provides a novel scheme for wavelength conversion enables ultra-fast conversion speed. On
the one hand, we utilize a three-wavelength-device (TWD) to reduce the recovery time of the SOA. On the other hand,
we use an optical band pass filter (OBF) which central wavelength is blue shifted with respect to the central wavelength
of the probe beam to increase the frequency response. The combination of a reduction of the SOA recovery time and an
increase of the frequency response enables conversion speed potentially to achieve 160 Gb/s or even faster.
In this paper, we demonstrated for the first time variable 1.5μm wavelength conversion through cascaded second order
nonlinear processes "SHG+DFG" by fan-out grating in lithium niobate waveguide. We fabricated the waveguide by
annealed proton exchange in periodically poled LiNbO3 (PPLN). The device used in this experiment is 4 cm long, has a
QPM period from 14.8μm to 15.2μm, waveguide width of 12μm, proton exchange depth of 0.7μm, and was annealed for
32h at 350°C. After proton exchange in pure benzoic acid using a SiO2 mask, the substrate was annealed in an oxygen
atmosphere. The wavelength of signal light was set at 1551.3 nm. The wavelengths of tunable pump lights we used in
experiment were 1543.2 and 1556.2 nm, and the corresponding grating periods were 14.87 μm and 15.03 μm,
respectively. The temperature was set at 100.5°C to avoid photo refractive damage and to match the QPM peaks to the
pump wavelengths. The conversion efficiency was about 10dB to be expected with the pump power 175mW in a similar
device with a slightly different QPM period and operated at 125°C.
All-optical wavelength converters (AOWCs) that utilize nonlinearities in semiconductor optical amplifiers (SOAs) have
attracted considerable research interest. AOWCs based on cross gain modulation (XGM) have a large dynamic range of
the input optical signal power but a low extinction ratio (ER) and a high chirp, whereas AOWCs based on cross phase
modulation (XPM) provide a low chirp and a high ER but suffer from a relative small input power dynamic range. We
point out that there seems to be some complementarity between XGM and XPM. Based on this, we propose a novel
scheme for cascaded wavelength conversion based on cross gain modulation and cross phase modulation in SOAs thus is
expected to have a high ER and a large input power dynamic range simultaneously. The wavelength conversion
operation includes two stages, that is, XGM in the first stage followed by the stage of XPM. In the XGM stage, we use a
band pass filter to increase the frequency response of the SOA. In the XPM, we use the bidirectional input scheme for
MZI to improve the response of XPM and cancel XGM-induced intensity unbalance to get a relative perfect interference.
A novel high-speed magneto-optic (MO) modulator which consists of an integrated wire grid polarizer (WGP), Bi-YIG
waveguide with cladding layer and conducting micro-strip line is proposed. With the integrated WGP, this MO
modulator is faster, more accurate and more stable because it is not only completely driven by electric signals but also
has no mechanically moving parts. Moreover, it is compact-structured and low-cost. Large Faraday rotation is obtained
with specific arrangement of the directions of the bias magnetic field and the modulation RF magnetic field. Optical
route and optic-electrical detect circuit are also designed and analyzed.
A micro high-speed 1×2 magneto-optic switch, which is used in high-speed all-optical network (AON), is designed and analyzed. The theoretical and experimental analysis of the micro high-speed magneto-optic switch mainly involves the parts of optical route, nanosecond impulser and high-speed magnetic field etc. The study of optical route covers design scheme of polarization optical route in the optical switch, the performance analysis of magneto-optic crystal by using Faraday Effect. The research of nanosecond impulser involves the design, simulation and test of electronic circuit diagram of nanosecond pulse. The analysis of high-speed magnetic field consists of magnetic path design in Faraday rotator and analysis of high-speed magnetic field etc. The nanosecond current pulse transient from nanosecond impulser is used to switch the magnetization of the magneto-optic crystal, which propagates a 1550nm optical beam. The experiment results state that nanosecond impulser can output the current pulse with impulse amplitude 10~60V and impulse width 10~ 100ns. The optical beam can be stably switched and the switching time is less than 1μs currently.
A novel type of 2×2 polarization independent magneto-optic switch with low Insertion Loss, nanosecond order switching time is designed and analyzed. The study of the magneto-optic switch involves two main parts: Faraday rotator assembly and optical route design. In faraday rotator design, magneto-optic crystal comparison and selection, two types of Faraday rotator assembly schemes design and analysis; high speed magnetic field simulation and generation; nanosecond trigger signal generator design, simulation and experiment are involved. Within optical router design, a simple but effective optical router with 2×2 mode is introduced. The nanosecond trigger signal supply to the Faraday rotator assembly is 12ns. The key characteristics, insertion loss, far-end crosstalk, switching time of magneto-optic switch that developed at a wavelength of 1550nm have been tested and root causes analyzed.
An all-fiber magneto-optic switch is designed in this paper, which makes use of Faraday Effect, fiber-type polarizing beam splitter/combiner (PBS/PBC), magneto-optic crystal fiber, nanosecond impulser and high-speed magnetic field control technology. The design scheme uses magneto-optic crystal fiber instead of bulky magneto-optic crystal. The optical route design includes linear layout of magneto-optic crystal fiber, the optical route design of polarized light in fiber PBS/PBC, magnetic route design and analysis of linear solenoid, etc. A solenoid which is driven by nanosecond current and can generate high-speed magnetic field is designed and manufactured. The result analysis shows that pulse signal can be greatly strengthened by impressed-bias static magnetic field which is perpendicular to transmission direction of light beam. Static magnetic field insures the intensity of induced magnetization where the light passes come back to original value, so that it can offer high-extent magnetization equality. The intensity of magnetic field can be improved to two orders when the length ratio of magneto-optic crystal fiber to solenoid is increased eight times. When the diameter of magneto-optic crystal and solenoid is decreased from three millimeters to one millimeter, the intensity of magnetic field can be improved to one order. The all fiber magneto-optic switch is slim in structure, flexible, easy to high-density integration and expansion, so there are many integration methods to design all-fiber magneto-optic switch array, which is characterized of smaller bulk, higher magnetic field usage, lower consumption and driving voltage, etc.
A novel micro high-speed 2x2 magneto-optic switch and its optical route, which is used in high-speed all-optical communication network, is designed and analyzed in this paper. The study of micro high-speed magneto-optic switch mainly involves the optical route and high-speed control technique design. The optical route design covers optical route design of polarization in optical switch, the performance analysis and material selection of magneto-optic crystal and magnetic path design in Faraday rotator. The research of high-speed control technique involves the study of nanosecond pulse generator, high-speed magnetic field and its control technique etc. High-speed current transients from nanosecond pulse generator are used to switch the magnetization of the magneto-optic crystal, which propagates a 1550nm optical beam. The optical route design schemes and electronic circuits of high-speed control technique are both simulated on computer and test by the experiments respectively. The experiment results state that the nanosecond pulse generator can output the pulse with rising edge time 3~35ns, voltage amplitude 10~90V and pulse width 10~100ns. Under the control of CPU singlechip, the optical beam can be stably switched and the switching time is less than 1μs currently.
In this paper, the contaminants on the substrate surfaces are cleaned using Q-switched pulse laser irradiation, which with pulse duration typically about 20ns and wavelength typically in the 1064nm or 532nm. A new mechanism for laser cleaning is proposed, which based on opto-acoustic effect that breakdown of the air above the target is obtained by a laser beam, and a laser-induced shock wave is produced to remove the various pollutants on the solid substrate surfaces. This method is much more effective than traditional conservative cleaning techniques including the continuous wave laser cleaning, there are many advantages for this new laser cleaning technology, such as the dry treatment, non-contact, non-damage to the substrate, no environmental pollution, and energy-economic, and so on. We make the theoretical analysis for this physical model of cleaning contaminant in detail and provided some experimental results and photographs.
It has been proved that gain volume scaling can be successfully applied to achieve high output power and a compact design. The waveguide material is metallic and diffusion-cooled, thus heat removal is more efficient. It is easy for the annular system consisting of two coaxial tubes to keep in shape and maintain mechanical stability. Annular gain media offer large gain volume with short axial dimensions. The resonator structure, principles of gain volume scaling and characteristics of the output power are presented in this paper. The outer diameter of annular waveguide walls is 20mm; an output power of 75W at wavelength 10.6µm has been obtained from a guide gap of 2.25mm and a gain length of 150mm. The annularly shaped output beam can be used directly for making holes. Moreover, according to its axisymmetrical structure and the law of refraction, by using two small prisms of the exact same material, it is possible to transform the annular beam into a solid beam by careful selection of the incident angle. Further, the diameter of the annular beam varies once the space between two prisms is changed.
A novel structure of micro-laser device is presented in this paper. Nd:YVO4 crystal is used as laser active medium, which thickness is 2mm. The array LD at wave-length 809nm is used as a pump source. The optical isolator plays a role in the eliminating back reflection in this system. The output power of 1.44W at 1064nm has been obtained for pumping power of 3W. The total optical to optical conversion efficiency and slope efficiency are 48% and 51.8%, respectively. And power stability <2% has been observed.
In this paper, an advanced high-power mini-waveguide CO2 laser for the industry is presented. The device is all made of metal materials. The two large annular electrodes are transversely excited by RF power. And the technique of diffusion cooling is used.
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