We propose and demonstrate a novel technique for efficient local fixing of photorefractive polymer hologram using a laser beam. In the new technique, a CO₂ laser beam is used to heat the sample and a local hologram can be fixed easily. By using glass and sapphire with particular thickness as the substrates for the photorefractive device, the hologram can be fixed efficiently and at much faster speed. The fixation efficiency can be greater than 80% and the hologram can be fixed in a few seconds. This technique is critical for dynamic holographic 3D display and holographic data storage.

Photorefractive beam fanning is observed in diffusion dominated materials such as barium titanate and photovoltaic materials such as lithium niobate. Beam fanning in barium titanate has been extensively used to generate self-pumped phase conjugation. Beam fanning patterns in lithium niobate have been utilized in characterization of the photorefractive material. Two types of beam fanning have been shown to exist: deterministic beam fanning which results from the shape of the beam, and random beam fanning which originates from scattering of the incident beam from the surface and bulk of the crystal. In this paper, we report on a careful analysis of both kinds of fanning, using a focused Gaussian beam of varying waists and incorporating randomness in amplitude and phase at the surface and through the bulk of the photorefractive material. We show that in photorefractive barium titanate, deterministic beam fanning, characterized by a deflection of the main lobe of the beam in the far field and an additional sideband, may dominate over waist sizes in the tens of microns, whereas random beam fanning, characterized by multiple lobes, dominate over waist sizes larger than tens of microns.

Optical trapping and transportation of microorganisms by the moving interference pattern was demonstrated with low-power (~50mW) HeNe-laser. Novel type of short-pulsed (ns) electrophoresis induced by photogalvanic effect is suggested and tested. We propose to use novel synergetic approach, based on synchronous application of optical trapping and pulsed electrical field for transportation and selective separation of solution components.

Taking into account parameters such as input pulse duration, peak power and dimension and dispersion of the nanofiber etc., using a femtosecond laser as a pump source and a nanofiber as a nonlinear element, we numerically simulated the supercontinuum generation (SCG). The results show that tapering the common fiber to nanometer-scale fiber provides tight field confinement and diameter-dependent dispersion, and narrowing the input pulse width to femtosecond could observe SCG easier. The relation between the spectrum broadening and the diameter of nanofiber is not a direct proportion. According to our simulation the dimension of the nanofiber plays an important role in changing dispersion and then the generation of supercontinuum.

We fabricate two phenanthrenequinone-doped copolymers which can improve the holographic recording characteristics of phenanthrenequinone-doped poly(methyl-methacrylate) (PQ/PMMA) photopolymer. In these materials, the polymer matrix of PQ/PMMA is modified to be copolymers, which composed of either poly(methyl-methacrylate-co -trimethylolpropane-triacrylate) or poly(methyl-methacrylate-co-acrylic acid 2-phenoxyethyl ester), respectively. With the chemical analyses of these materials before and after light exposure, we investigate the physical mechanism of the holographic recording in those copolymer samples. In addition, the holographic characteristics of different samples, including dynamic range and sensitivity, have been measured. These experimental results demonstrate that modification of the monomers is an efficient method to improve the material properties.

Electron paramagnetic resonance (EPR) under the conditions of in situ laser illumination of the sample in the microwave cavity, called photo-EPR is an excellent method to detect photo induced electron transfer in real time. We report Photo- EPR results on the formation of clusters of magnetic ions in 0.67Pb(Mg_1/3Nb_2/3)O₃. 0.33PbTiO₃ (PMN-PT) on illumination with blue laser at room temperature .The Photo EPR signal with g=2.00, agrees with Pb³⁺ formation. The PMN-PT crystals 2-6mm size grown using PbO flux method were clear and transparent: and the upper part of the melt yielded pink colored crystals containing a few hundred PPM of Fe³⁺ as seen by EPR Signal at g=4.3. The large linewidth (~45 Gauss) of the photo-EPR signal and the presence of Fe³⁺ in the sample suggests the possibility of magnetic ion cluster formation on blue laser excitation. When the photo-magnetic centers were produced in magnetic field of 7.5KG, the signal was 30% more than that produced under switch-OFF condition of magnet having a remnant field of only 50G. This critical observation is a clear pointer to the formation of photo-induced magnetic polarons at room temperature, which are essentially clusters of ferromagnetically, coupled Fe³⁺ , Pb³⁺ and trapped electrons. The cluster formation and decay exhibited fast optical response with growth and decay time less than or equal to 100msec. These observations show that PMN-PT having excellent electromechanical properties can also be used for photomagnetic switching and real time holography with fast grating response using Pb²⁺ <--> Pb³⁺ process. PMN-PT would have additional advantage compared to other photo-refractive materials: due to possibility that the grating contrast can be manipulated by external magnetic field.

The Global Positioning System (GPS) Guidance Package (GGP) Program developed an affordable, navigation-grade, miniature guidance package based on a tightly coupled, integrated combination of a Miniature GPS Receiver (MGR) and miniature Inertial Navigation System (INS) including associated processors and Adaptable Interface Unit (AIU) functions. The GGP INS used Interferometric Fiber Optic Gyroscopes (IFOGs) and micro-machined silicon accelerometers. Several key challenges were met by the GGP Program. The first key challenge and the focus of this paper is the development of the navigation grade IFOGs. These gyroscopes, with a drift requirement of less than or equal to 0.01 degree per hour, enable pure inertial navigation at or less than 1 nautical mile per hour error growth. Also, IFOGS offered the potential for low cost by avoiding the precision optics assemblies of in-production navigation grade Ring Laser Gyroscopes (RLGs). The success in producing the IFOG was greatly benefited by a companion program: the Flexible IFOG Manufacturability Program. This program involved developing machinery for automated assembly in areas such as integrated optical circuits, fiber couplers, solid state light sources and precision fiber coil winding. The successes of this program resulted in reducing fabrication time, increasing performance, increasing yield and reducing cost. For example IFOG fabrication process time for one system contractor was reduced from eight days to 12 hours by automating the coil winding. This enabled not only the timely production of gyros wound with more than 1000 meters of fiber for GGP but also enabled a lasting manufacturability legacy for future INSs.

The field of fiberoptic gyroscopes, FOGs, was born after a brief publication by Vali and Shorthill in 1976 proposing the use of a multi-turn, single-mode fiber to enhance the sensitivity of a Sagnac interferometer by the number of turns in the fiber coil. It was this simple concept that encouraged many researchers in universities and in industry to get into this field and to develop fiberoptic gyroscopes for a variety of applications, including high precision ones as needed for navigation. The fortuitous developments that led to the 1976 publication are disclosed to show what really went on behind the scenes during the year preceding this publication.

High accuracy polarized fiber optic gyroscopes require sensor coils comprised of relatively expensive polarization maintaining fiber. While this fiber insures minimal polarization cross coupling and thus increased sensitivity, the long required fiber lengths result in sensor coils that are quite expensive. Reduced cost single mode fiber based coils are attractive, but exhibit poor polarization selectivity due to cross coupling that manifests as signal fading and reduced detected signal amplitude. Moreover, random birefringences induced at fiber crossover points impart a nonreciprocity that tends to exacerbate this problem. A crossover-free winding scheme employing a single mode fiber wound in an Archimedean spiral can potentially improve the performance of single mode fiber coils by eliminating these random birefringences, thereby improving coil sensitivity. As well, the bending induced birefringence of these coils can serve to improve polarization maintenance. Geometric and polarimetric analyses of spirally wound coils describing the effects on overall Sagnac area, bending induced birefringence, and polarization mode coupling are examined here. The spatially varying induced birefringence, beat length, and associated mode coupling are modeled and it is found that elimination of the cross coupling due to random crossovers renders the spiral geometry potentially useful for high accuracy inertial guidance systems.

The DoD goals for inertial sensors have included achieving high accuracy performance and small size at a low cost. This goal has always been a challenging endeavor, since small size and high accuracy have often been costly and technically difficult to achieve. In 1998, the Army patented a fiber sensor coil winding concept that would facilitate the opportunity to make the Fiber Optic Gyroscope (FOG) more competitive in cost with relation to the commonly-used Ring Laser Gyro (RLG). Recent advances in FOG sensor coil winding techniques appear to show great promise in the improved performance. The novel Crossover-Free (CF) winding technique eliminates fiber crossovers and allows the use of inexpensive single-mode fiber (SMF). Experiments were conducted with the use of an analog, open-loop testbed, which was characterized with a 1 km quadrupolar SM sensor coil. Various sensor coil configurations were spliced into the FOG testbed and bias drift tests were conducted. Different fiber lengths, coil diameters, and fiber wind configurations were evaluated. The Crossover-Free sensor coils were precision wound by a semi-automated Fiber Placement Machine (FPM) developed by Stanley Associates. The Crossover-Free sensor coils test results are compared to standard precision wound coils. The bias errors caused by the fiber crossovers in standard SM sensor coils are also discussed and compared to the near elimination of the crossovers in the CF design.

Over thirty five years have elapsed since the fiber optic gyro was proposed by Vali and Shorthill. In those decades, fiber gyros have matured. They are competing head to head with existing technologies such as mechanical gyros and RLGs in tactical, navigation and strategic applications and are winning. Northrop Grumman has produced the majority of fiber optic gyros and fiber optic gyro based inertial products in the world. This paper will cover the various Northrop fiber gyro products, the platforms they are used on, as well as production and top level system data.

In the late 1970s the closed loop fiber optic gyro was invented and demonstrated at McDonnell Douglas Astronautics Company in Huntington Beach, California. This development was followed by a series of derivative inventions that included the Sagnac acoustic sensor, Sagnac distributed sensors and finally a Sagnac secure fiber optic communication system. This paper provides an overview of these developments.

Fiber Optic Gyro (FOG) coils have traditionally been produced by cylindrical winding techniques. Regardless of the type of cylindrical wind, standard or quadrupolar, the resulting coils contain fiber crossovers that degrade performance. In 1998, the U.S. Army patented a fiber coil configuration that essentially eliminated crossovers, was thermally symmetric, and allowed the use of inexpensive single-mode (SM) fiber. The crossover-free fiber optic gyro (CFOG) necessitated a paradigm shift in coil production methodology. The CFOG coil design was analyzed in depth to determine manufacturability. Design enhancements were made to enable automated high speed fabrication, resulting in the Improved Crossover-free Fiber Optic Gyro (ICFOG). A prototype Fiber Placement Machine (FPM) was designed and constructed to produce CFOG coils. The fiber placement concept was verified by producing test articles and complete coils.

Highly accurate, compact, and low cost inertial measurement units (IMUs) are needed for precision guidance in navigation systems. Active and passive polymer materials have been successfully used in fabricating two of the key guided-wave components, the phase modulator and the optical transceiver, for IMUs based on the interferometric fiber optic gyroscope (IFOG) technology. Advanced hybrid waveguide fabrication processes and novel optical integration techniques have been introduced. Backscatter compensated low loss phase modulators with low half-wave drive voltage (V_π) have been fabricated with CLD- and FTC- type high performance electro-optic chromophores. A silicon-bench architecture has been used in fabricating high gain low noise transceivers with high optical power while maintaining the spectral quality and long lifetime. Gyro bias stability of less than 0.02 deg/hr has been demonstrated with these components. A review of the novel concepts introduced, fabrication and integration techniques developed and performance achieved are presented.

Using a simple transmission line analogy and transfer matrices, we model optical propagation through one-dimensional photonic bandgap structures. Our objective is to analyze the frequency response of the reflectivity and transmittance in such devices with varying refractive index change, material thickness, angle of incidence and in the presence of possible defects. Our results should prove useful in providing guidelines for selection of optical materials such as photorefractives in which such bandgap structures can be programmably induced.

Automatic target recognition (ATR) can be accomplished by many methods, including recognition of vibrometric signatures. In many cases, ATR is enhanced by photorefractive amplification, a two-wave mixing effect in which two input beams form a dynamic holographic grating. One of the two beams (the pump) diffracts from that grating into the other (the signal), assuming the characteristics of the signal. When the pump is much stronger than the signal, the diffracted pump becomes a highly amplified signal beam. Traditionally, however, the frequency at which this amplification can be applied is limited to <1/2πτ₀, where τ₀ is the decay time of the grating in the absence of a pump or signal. We demonstrate that the amplification has no such limit in the case of vibrometry, which measures frequency-modulated, rather than amplitude-modulated, signals. This is shown by constant photorefractive amplification at frequencies up to >700 kHz in Cu:KNSBN, which has τ₀ >100 ms (corresponding to a maximum amplification frequency of 1.6 Hz).

In this paper, we provide a technique using a hologram as a diffractive element for finding the absolute shape of an object with large depth discontinuities. The proposed method offers following major advantages: (1) a large depth-of-field in the projection system, (2) very low fringe distortion (even for a large field of view), (3) only one phase measurement needed for operation, (4) easiness for calibration, (5) robust performance to analyze surfaces with lots of discontinuities, especially for automatic phase unwrapping, and (6) a very compact design for the measurement system. The single-shot property also makes it possible for measurements of dynamic objects with large depth discontinuities.

A unique all-fiber tunable filter is based on the combination of a single resonant band long period grating (LPG) and an electro-optic polymer second cladding layer. The single resonant band LPG is fabricated by etching the cladding of a 125 μm thick fiber and using ultraviolet (UV) illumination to write the grating. Once a single resonant band has been achieved, an ITO electrode is sputtered onto the thin silica cladding and then a polymer second cladding layer is applied. The refractive index of the polymer determines the resonant wavelength of the filter. After a second electrode is coated onto the second cladding, the polymer index is tuned by applying an external electric field. Recent modeling and experimentation has shown that a high index ITO inner electrode can increase the tuning range of the filter up to 10 times by inducing cladding mode transitions.

Mach-Zehnder interferometers (MZIs) are used in many optical applications, such as measurement of the coherence length of a laser, thermal dynamic flow, flatness of plane optical plates, thickness of thin films, etc. In this type of interferometer, light passing through a sample region in one direction recombines with a second leg without traversing the sample twice. In telecommunication, MZIs are used for demodulating differential phase-shift-keyed (DPSK) signals. DSPK has attracted increased attention in fiber optic transmission in recent years because of its 3-dB optical signal to noise ratio improvement over standard intensity modulated transmission, as well as for its high tolerance to nonlinear effects and coherent crosstalk. In a standard fiber MZI, two wideband fiber couplers are spliced together with one arm providing a one-bit delay to convert the phase difference into an intensity modulation. In our alternate type of MZI, the two-mode interferometer, the time delay is obtained through the difference between the propagation constants of two modes instead of through a physical path length difference. We present here a novel single multimode fiber modal interferometer for DPSK demodulation. In this design, a second mode is excited by splicing a standard fiber to a multimode fiber length such that two modes beat together before recombining in a second splice. A numerical analysis and an experimental verification of the multimode fiber parameters to maximize the extinction ratio and minimize the length of the interferometer are presented. We investigate coupling, insertion losses, temperature sensitivity and polarization effects of using modes with and without radial symmetry. The design is extremely low-cost, easily manufactured and is intrinsically less temperature sensitive than standard MZI. Although balanced detection is lost, DPSK may still be advantageous because of its high tolerance to nonlinear effects and coherent crosstalk.

This paper discusses some ways to use acousto-optic devices for controlling optical beams in high-power laser systems. As a medium of interaction, TeO₂ crystals grown using a specially developed technology are suggested. Some examples of the use of the developed acousto-optic devices in high-power laser systems are presented.

A detailed investigation of surface acoustic wave (SAW) propagating in x-cut y propagation lithium niobate (LiNbO₃) for integrated acousto-optic tunable filters (IAOTF) is reported in this paper. With getting curves of velocities, the walk-off angular (the angular between the power-flux vector and the propagation direction) can be obtained by the cubic spline interpolation method. The electromechanical coupling constant curve is given. Now, an optimal configuration of IAOTF has been designed, in which the direction of interdigital transducer should be inclined about 4.18°.

In this paper, diffractive optics analysis methods for plasmonics circuits with dielectric substrate and surface plasmon resonance phenomena occurring in metal/polymer structures are presented. For plasmonics circuit analysis, the nonperiodic rigorous coupled wave analysis method with perfect matched layer is developed. Based on the nonperiodic coupled wave analysis framework, the identification method of eigen-surface plasmon modes that can exit on metallic strip structure with arbitrary shaped cross-section are presented. The three-dimensional plasmon wave propagation on plasmonic circuits is analyzed with field distribution visualization. The rigorous coupled wave analysis for surface plasmon resonance phenomena is also presented. Surface plasmon resonance phenomena induced by various optical sources are analyzed with field distribution visualization.

Micro-structured Er³⁺ - Tm³⁺ co-doped tellurite fiber with three rings of holes was fabricated using a soft glass drawing tower by a stack-and-draw technique. Amplified spontaneous emission (ASE) around 1550nm band were observed when pumped with both, 980nm and 790nm, lasers.

Besides the well-known LiNbO₃, ferroelectric strontium barium niobate (SBN) crystals are attractive for electrooptic modulation applications because of their high electrooptic coefficients and low half wave voltage. Their EO properties, typically obtained under low frequency electric field driving conditions, contain both primary and secondary contributions arising from electromechanical coupling. Single crystal fibers (Sr,Ba)Nb₂O₆ and LiNbO₃ grown by laser heated pedestal growth method are investigated to explore the frequency dependence of electrooptic property both for mechanically stress-free crystals (low frequency) and at microwave driving frequency of 10GHz. An optical pulse can be up-tuned/down-tuned, squeezed/ expended in the range of GHz using a single piece of SBN crystal fiber under a moderate microwave field, controlled by the relative position of optical pulse traversing the crystal fiber to the microwave field. The effective microwave-photonic interactions demonstrated in ferroelectric SBN crystals provide a potential solution for the bandwidth definitions and wavelength tuning applications. The experimental configuration and the analysis are also of general significance in electrooptic property studies at microwave frequencies.

The Opto-electronic Technology Lab of Chongqing University (OTLCU) has been working on bridge structural health monitoring using fiber optic sensors in the past decade. A remote sensing network based on the Extrinsic Fabry-Perot Interferometer (EFPI) fiber sensor was developed and implemented on several large bridges in Chongqing, China. In this paper, a brief review of the OTLCU's research progress in this field was presented. Contrastive experiments between the EFPI strain sensor and the electrical strain patch (ESP) were introduced. Both internal embedding and surface mounting of the EFPI were studied. The design of the sensing network and two implementation examples were discussed, and some representative monitoring results were given.

It is very critical to develop sensor that can operate in high temperature and chemically harsh environments. Sapphire (Al₂O₃) material, which possesses a melting point of 2050°C and a wide transmission wavelength region as high as ~3.5μm, has been demonstrated to be an ideal candidate for high temperature fiber-based environmental sensing applications. Under harsh environment, the performance of conventional blackbody radiation based sapphire fiber high temperature sensor could be easily affected due to the lack of cladding. In this paper, a fiber-optic temperature sensor with a single-crystal sapphire fiber as the light guide and a high temperature ceramic coating as the sensing element as well as the protection layer was presented. The radiance emitted from the ceramic coating is used to measure the temperature, and it is transmitted to optical receiver through the sapphire fiber. This ceramic coating greatly improved the stability and dynamical range of pyrometer. Preliminary experimental results demonstrated that the sensor is very promising for measuring ultra-high temperature up to 1900°C in the harsh environment.

Integrated Gasification Combined Cycle (IGCC) power plants have great potential for future clean-coal power generation. Today, the quality of coal is measured by sampling coal using various offline methods, and the syn-gas composition is determined by taking samples downstream of the gasifier and measured by gas chromatograph (GC). Laser induced plasma technology has demonstrated high sensitivity for elementary detection. The capability of free space transmission and focusing of laser beam makes laser induced plasma a unique technology for online compositional analysis in coal gasification environment and optimization control.

Dynamic response characteristics of silica fiber long-period grating with a modified cladding, composed of ∼10-100 nm nanoparticle palladium oxides thin film material prepared by a magnetron sputtering technique, have been investigated at several elevated temperatures with a 2%H2/98%N₂ mixing gas concentration. The fiber cladding modified grating, without cladding chemical etching process, demonstrates 540 pm per 1% H₂ sensitivity, a better than 1sec response times at 160^oC, respectively. The thermal responses of the prototype have demonstrated increased dynamic wavelength shift while reducing response time simultaneously. The observed thermal dependence of the prototype could be attributed to a combined effect of thermal dependent hydrogen atoms diffusion rate and hydrogen atoms solubility.

Using the two-dimensional coupled-wave theory, the diffraction characteristics of volume holographic gratings (VHGs) with finite size planar are studied for the ultrashort pulsed beam (UPB) readout. Numerical simulations are show for the special case of the overlapping VHGs reconstructed by a Gaussian-shaped UPB in temporal domain. The effects of the material dispersion and the finite size of the grating on the intensity distributions of the diffracted and transmitted pulsed beams, and the total diffraction efficiency are given. Our study also shows the differences between the diffraction characteristics of the finite size planar VHG for the UPB readout and those for the CW readout. And, comparison of the diffraction characteristics between the finite size VHGs and the one dimensional VHGs under the UPB readout is given.

An oscillatory characteristic of diffraction is observed during holographic recording period in an oxidized LiNbO₃:Cr:Cu crystal with 514 nm green light as the recording light and 390 nm UV light as the sensitizing light. The optimal switching time from the recording step to the fixing step for high diffraction of a fixed hologram is studied. It is shown that switching after the first diffraction maximum leads to higher fixed diffraction efficiency. The theoretical explanation is presented according to time-space dynamic theory of the nonvolatile holographic recording in doubly-doped LiNbO₃ crystals.

In this paper, the theory model in which both the two-center material equations and two-dimensional two-wave coupled equations were solved jointly based on two-center holographic recording method is presented to analysis the dynamic formation of the crossed-beam photorefractive gratings in two doped LiNbO₃ crystals. The influence of the light intensity on the basic holographic properties of the crossed-beam photorefractive gratings in LiNbO₃:Fe:Mn crystals is explored. The numerical simulation results are presented. The investigation yields quantitative predictions of the expected behavior of the dynamics of these gratings, which can be useful for the design of finite boundary photorefractive holographic optical elements.

LiNbO₃:Fe:Ru crystal is the effective recording media with high recording sensitivity for two-center recording, and the physical mechanism for the high recording sensitivity is investigated theoretically and experimentally. The results show that the energy level of Ru perhaps is closer to that of Fe than that of Mn in LiNbO₃ crystal, the electrons in Ru center can be excited more effectively into the conduction band in the same sensitizing conditions, which can induce the improvement of the recording sensitivity. The recording sensitivity 0.044cm/J in LiNbO₃:Fe:Ru crystal, which is ten times larger than that obtained in LiNbO₃:Fe:Mn reported early. However, the elevation of energy level of deep center will induce that the electron excitation from deep center by the recording light become more effective, and the persistence decreases with the recording sensitivity increase, the grating in Ru center can be erased by red light obviously. In practical application people must take a trade off between the recording sensitivity and persistence.

The photorefractive volume holographic cylindrical lens taking on the wavelength conversion and the wave-front conversion synchronously was designed. Based on coupled wave theory, the wave-front conversion by local photorefractive volume holograms between cylindrical and plane waves which recoded at 632.8 nm and reconstructed at 800 nm is studied. The off-Bragg parameter at arbitrary point of the hologram in the reconstruction process is analyzed. The dependences of diffraction efficiency on the focal length of recording cylindrical wave and on the geometric size of the gratings on the hologram are discussed in detail. The amplitude distribution of the diffracted beam at the output boundary is also analyzed. Furthermore, the effect of selectivity of different on-Bragg reference point for recording hologram on the diffraction efficiency of the grating is discussed.

The physical response of photorefractive materials under inhomogeneous illumination is well described by using material equations. Usual solutions to material equations are based on the assumption that the light modulation is small enough to linearize the equations. However, large light modulation, the presence of applied electric field and short time pulses are always required in many applications. A few analytical approaches and numerical solutions are developed for large light modulation. But certain simplifications are applied to the set of material equations and large computational effort is required. In this paper we present a numerical approach based on method of lines for simulating the photorefractive kinetics at high light modulation with an applied electric field. No approximations are made during the simulation and less effort is required during computation. We use different values of light modulation and applied electric field to present the numerical results. Time-space distribution of the carrier density and the space charge field, field amplitude evolution are obtained. Compared to the results under the small light modulation approximation, this method helps to understand the dynamics of photorefractive grating formation at high light modulation. A comparison is also made between the coupling coefficient obtained by this numerical method and that by analytical expressions.

The volume holograms recorded by use of 90-degree geometry with reference and signal beams entering orthogonal crystal faces, have been widely used in fields such as waveguide couplers, holographic lenses, high-density holographic data storage. They posses the peculiar advantageous of small volume, ease of integrating and cascading. In fabrication of volume holograms are capable of converting various wavefronts into each other with high efficiency. But most of the researches were based on on-axis holographic optical elements such as cylindrical lens or spherical lens but not 90-degree geometry. In this paper, we investigate the properties of holographic lenses capable of converting plane waves into spherical waves in a perpendicular direction. Our research submits an analytical integral solution for the wavefront conversion problem in 90-degree geometry. The results can be of great practical importance in the design of volume holographic optical elements.

The domain inversion and electrochromism in congruent RuO₂:LiNbO₃ crystals are investigated at room temperature, and the relations between them are proposed. During electric poling process, the electrochromism accompanies the ferroelectric domain inversion simultaneously, and is localized to the same region with domain inversion. As domain inversion, the electrochromism is completely reversible when the domain is inverted from the reverse direction. The properties, coincidence and localization, between domain inversion and electrochromism are proved solidly by the digital holographic interferometry, the real-time measurement of optical transmittance change and poling current, and the micrographic analysis after being etched in hydrofluoric acid. The influences of annealing conditions on electrochromism are also discussed. We provide the reasonable assumptions and analyses that the charge redistribution within the crystal caused by domain inversion is the source for electrochemically oxidation and reduction of Ru ion, and the intervalence electron transference between Ru⁴⁺ and Ru³⁺ plays a key role in the spectrum shift within different spectral range by the change of the photon absorption.

Double-functional (optical and electrical) interferometer was realized using holographic recording of dynamic gratings in the semiconductor crystal of CdTe:V. Two mechanisms of holographic phase grating recording is considered: electro-optic effect (relatively slow, in microsecond) and free-carrier gratings {Drude-Lorentz nonlinearity, fast response in nanoseconds). Both, electrical and optical signals from electro-optic gratings were strong enough to make direct registration on oscilloscope (without preamplifiers) using infrared (IR) CW (λ = 1064 nm) diode pumped 100 mW laser. Step-like phase modulation mimics the pulsed ultrasound modulation, used in biomedical acoustophotonic imaging. Theoretical approach is in agreement with experimental results.

A rigorous mathematical modeling of the total internal reflection holography based on the pseudo-Fourier modal analysis theory is proposed. The analytical three-dimensional Fourier transform representation of general three-dimensional holograms developed by the total internal reflection holography is described. The generalized three-dimensional pseudo- Fourier modal analysis method is presented for solving the Maxwell equations. A few numerical examples of the total internal reflection holography obtained with the proposed method are provided.

In this paper, a projected fringe profilometry using a supercontinuum light source generated by launching femto second laser pulses into a highly nonlinear photonic crystal fiber is presented. The proposed profilometry for micro-scale measurements has the following major advantages: (1) large-depth-of-field in the projection system, (2) ease of calibration, and (3) little speckle noise.

In this contribution, we propose a design algorithm to create three-dimensional objects by using CGH technique with the Iterative Fourier Transform Algorithm (IFTA) for designing computer generated phase holograms. One example of the designed phase hologram is simulated, and computer simulated reconstruction are presented. In addition, we measure the phase and amplitude modulated characteristic of reflective LCSLM by Michelson Interferometer. By using this commercial device, designed CGHs can be dynamically displayed and the real-time reconstruction of 3D images can be optically achieved by a Fourier transform lens. We also will demonstrate experimentally the optical reconstruction for real-time 3D images.

An important issue in developing applications for photopolymers in holography is the effect of diffraction efficiency on recording properties although acrylamide derivative monomers had been widely used in polyvinylalcohol-based film. Now it is possible to create these samples with a fine particle sizes choice than was previously available. We exploit these recent advances in photopolymer processing to systematically evaluate how the diffraction efficiency of a photopolymer depends on its surface silica particle size. In this paper illustrate that sample diffraction efficiencies higher than 85 % can be reached and the effective thickness used to record the hologram is around 1.0 mm.

In this work, an investigation of the tuning characteristics of electrically tunable long-period gratings (LPGs) is presented. A precise four-layer model is used to quantitatively analyze the tuning potential of the gratings and experimental data is provided to support the analysis. The four-layer model includes a silica core layer with an inscribed LPG, a thin silica cladding layer (~40 μm), an ultra-thin (~ 50 nm) high refractive index indium-tin dioxide (ITO) inner electrode layer, and a tunable electro-optic polymer layer. It has been found that the inner electrode layer, made of high refractive index ITO, can be modeled as a high index overlay and causes the forward propagating modes in the thin silica cladding to reorganize as the ambient refractive index changes. This reorganization effect can lead to a significant increase (10 plus fold) in the tuning range of LPG tunable filters. Moreover, the required specifications of the tunable polymer layer are quantitatively analyzed. Finally, the required characteristics of the electro-optic polymer are realized by using a nano-composite of zinc sulfide and ferroelectric relaxor poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) terpolymer.

In this paper, we review currently available fiber-optic gyroscope (FOG) technologies and major noise factors limiting the performance of FOGs. We investigate possible solutions to noise factors including Rayleigh backscattering, Kerr effect, Faraday, and Shupe effects. Based on these solutions, we present the possible design of an interferometric FOGs employing microstructured fibers. A supercontinuum source can minimize Rayleigh backscattering and Kerr effect by reducing the coherence length of FOGs. Also, by using a photonic bandgap fiber with hollow core, Kerr, Faraday and Shupe effects can be minimized.

In this paper, we theoretically and experimentally demonstrate that the major drawbacks of current beam scanning systems can be drastically reduced. First, the scanning speed of several MHz level has been achieved using an optical phased array. Since the increased scanning speed causes the lower scanning resolution due to the less number of pulses per pixel, multiplexing techniques to increase the repetition rate of a beam scanner have been demonstrated. The fiber multiplexing techniques have been demonstrated in serial and parallel configurations, which can be selected for different requirements and applications.

Fiber optic extrinsic Fabry-Perot interferometric (EFPI) sensors are widely used in dynamic pressure measurements because of their inherent advantages including small size, light weight, high sensitivity, high frequency response, electrical passivity, electromagnetic interference immunity (EMI), and single-point measurement. However, small fluctuations of background pressure could shift the operating point of the sensor in an unpredictable way, which introduces a nonlinear response in dynamic pressure measurements. In this paper, we present a novel open structure only 125 μm in diameter to eliminate the operating point dependence on background pressure fluctuations. The essential element is a piece of hollow fiber, which connects a standard telecommunication fiber and another hollow fiber with a smaller inside diameter to form a Fabry-Perot cavity. The structure is open to the environment by a small hole, which allows gas exchange between the sensor cavity and the ambient atmosphere. On the other hand, the sensor is capable of responding to acoustic pressure because of the slow gas exchange through the small hole. In addition, this all fused silica structure features high temperature stability, good linearity, and high repeatability.

In this paper, a new speckle based hologram multiplexing recording technique is proposed and tested. In this method, a multi-mode LiNbO₃ single crystal fiber is employed to generate speckle patterns which are used as reference beams in hologram recording process. The speckle pattern generation can be precisely controlled by external E-field. Theoretically, this technique can generate thousands of decorrelated reference beams at given practical constraints. Its storage capacity can be scaled up as material properties are improved, making it well adapted to new material development. A theoretical analysis and numerical simulation of speckle pattern generation are also presented in this paper.

We report a new kind of single incident beam holography. In this method, we use only one beam instead of two beams to make gratings inside photorefractive cerium doped barium titanate. The configuration of the method is based on an anisotropic self-diffraction scheme. The reflection of self-phase conjugate beam at the surface of incidence plays the role of the second beam. By using the reflection of the self-phase conjugate beam, the difficulty of alignment between two focused writing beams has been eliminated. The autocorrelation images in non-Bragg orders have been monitored in order to verify the effectiveness of this method for writing holograms.

We propose and describe an optoelectronic system that emulates a minimum digital system; which typically consists of a microprocessor, a memory device, an input device and an output data device, with its corresponding data, control and addressing busses. These devices work following a program which is stored in the memory device, as codified instructions. In our proposal, the memory device is a reconfigurable single-lens holographic memory. The instructions to be stored are coded and decoded as binary pages by software. The software interprets the data and carries out the instructions as a microprocessor does in a minimum digital system. We present preliminary results of the performance of our proposal.

We have developed the design method for planar holographic Bragg reflectors by layer-peeling algorithm. We have modified the layer-peeling algorithm to synthesize planar holographic Bragg reflectors. We use iterative layer-peeling algorithm with fabrication constraints to solve the difficulties of fabricating the negative parts of apodization and shorten the length in planar holographic Bragg reflectors. The novel designs for the passband WDM filter that we have demonstrated is easier to manufacture.

In this work, the recent work on fabricating harsh environment fiber grating by femtosecond laser and applications as multi-parameter sensor is reported. Bragg gratings have been written in single mode (SM), multimode (MM) silica fiber, polarization maintaining (PM) single mode silica fiber, and highly multimode 60-micron thinned sapphire fiber. Silica gratings can survive in temperatures higher than 1000°C. Sapphire fiber grating can even go as high as 2000°C. Multiple parameter integrated fiber sensor that can detect vector bending and ambient temperature simultaneously with a single asymmetric fiber Bragg grating is realized in MM silica fiber and PM silica fiber. Higher order modes of sapphire Bragg grating is filtered out by mode winding to realize single mode operation.

Bismuth Iron Gallium Garnet (BI₃Fe_5-xGa_xO₁₂, BIGG) has been synthesized by pulsed laser deposition method and their comprehensive characterizations are reported. X-ray diffraction analyses have proved that the BIGG films are of good epitaxial quality. Faraday experiments verify the BIGG's high Faraday rotation. BIGG film is more transparent than Bismuth Iron Garnet film especially at wavelengths shorter than 550nm. Figure of merit of BIGG films θ_F/-log (T)are greatly improved than that of original BIG films. High speed pulse response experiments of our BIGG films have reached 5ns.

In this paper, we will present our preliminary results on our development of infrared and terahertz generation by ultrafast laser pulses. The objective of this project is to develop (i) portable and cost effective spatially coherent broadband Infrared (IR) and Terahertz (THz) illuminating light sources. To effectively generate spatially coherent broadband IR and THz sources, we use a novel nonlinear optical technical approach by harnessing the huge nonlinear effect of the specially designed and fabricated photonic crystal fibers (PCF). The major merits of these unique light sources are: (1) broad band (covering a wide range of spectroscopic signatures), (2) spatially coherent (so that beams can be delivered to the far distance like laser beams), (3) compact, portable and small footprint (all fiber design), (4) cost effective (traditional approaches such as cascaded laser systems are complicated and expensive for covering broadband).

A zinc oxide (ZnO) single crystal microtube fabricated by using an encapsulated microwave-heating growth method has been reported. This microtube has a highly symmetrical hexagonal tubular structure, and exhibits strong near-band-edge emission, highly selective UV light response, and excellent electron field emission. In this paper, we study the converse piezoelectric properties of the microtube by using a sensitive modified Michelson laser interferometer. The experimental results demonstrate that this hexagonal hollow structure has very interesting piezoelectric properties compared with bulk ZnO crystals.

Undoped and Mg-doped stoichiometric LiTaO₃ with concentrations of 0.5, 0.7, and 1.0 mol % were grown by the double-crucible Czochralski method, and their photorefractive effect was investigated by measuring light-induced birefringence changes. Periodically poled Mg-doped stoichiometric lithium tantalate (PPMgSLT) were fabricated for QPM optical parametric oscillator, whose properties, including slope efficiency and threshold, were measured to investigate influence of photorefractive effect on optical parametric oscillator. The results showed that a concentration of 1 mol % MgO in the melt was enough to suppress photorefractive effect at tens of MW/cm², and the OPO performance of PPMgSLT doped with 0.5 mol % MgO is only 6 % lower than that of PPMgSLT doped with 1 mol % MgO at room temperature, even though light-induced birefringence existed for the crystal doped with 0.5 mol % MgO.

Based on the coupled wave theory of Kogelnik, variations of the diffracted and transmitted beams with time are theoretically studied when PR hologram is illuminated by femtosecond pulse. We find that the waveforms of the diffracted and transmitted pulses depend on the input pulse duration, grating spacing, crystal thickness and modulation of the refractive index. By changing values of these parameters, the diffracted and transmitted pulse waveforms can be controlled to satisfy our desire. We also find that the diffracted and transmitted pulses have a displacement along the t-axis comparing to that of the input pulse. Conclusions of our study can be used in many areas, such as pulse shaping and signal processing.