We have developed an in-situ single wavelength ellipsometer applicable to a vacuum sputter to monitor ellipsometric parameters during thin film deposition. The translation and tilting stages in the polarizer and analyzer make it easy to adjust optical axis and the angle of incidence. To calibrate inherent offset in the azimuth axis of the polarizer and analyzer, regression and residual calibration procedures are conducted. This work also includes the measurement results of the silver target deposition on the alloy, made of chrome and nickel, and silicon wafers. The manufactured ellipsometer will be used to investigate optical properties of the thin film and substrate in the vacuum state with various temperature ranges.

We present the real time polarimeter with a micro retarder array consisting of subwavelength gratings with different directions. A 2x2 form-birefringent micro retarder array was fabricated with an electron-beam lithography method and a reactive ion etching technique. Each retarder was a TiO₂ grating with 300-nm period on a silica substrate, and the phase retardance was 0.31 (pi) for 633-nm wavelength light. Using the fabricated retarder array, the real time polarimeter was made. The micro retarder array and a linear polarizer film were stacked up on a 2x2 photo-detector array. Four Stokes parameters were computed at a real time rate from outputs of the detector array. We could measure temporal change in polarization states of light by simple experiments.

This paper describes a method and device for measurement of two-dimensional retardance and dispersion with high-order and azimuthal direction. The system consists of a white light source, crossed polarizers and a detector for spectroscopic polarized light. A spectroscopic interferogram shows sinusoidal to wave number change, and its period changes slightly because of dispersion of birefringence. Fourier transform method is used to analyze the birefringence from the spectroscopic interferogram. One hundred and twenty-eight sets of images are used for birefringence analysis. Some results of 2D birefringence distribution with dispersion are shown for the demonstration.

This study deals with a method for multiplying and extracting continuous isochromatics from color photoelastic fringes obtained in plane polariscopes with a tricolor light source. In the method, isochromatics are taken using a color CCD camera in dark-and light-field plane polariscopes. The four color images, which contain both isochromatic and isoclinics, for the dark and light fields are used to obtain only color isochromatics. The color isochromatic images are separated into R, G and B images. The number of fringes is trebled when the three color images with extracted fringes of 0.5, 1.5, 2.5,... order are superimposed. In order to investigate the effectiveness of the multiplication and extraction, this method was applied to color photoelastic fringes obtained in an epoxy resin plate under 4-point bending.

The difference of optical scattering intensity distributions in the directions along and across the fiber can be used to ascertain wood fiber orientation. However, it is difficult to measure the fiber orientation of wood with rough surfaces, due to the overwhelming of the difference by the scattering from the uneven surface. It has been experimentally found that under polarization detection the peak positions in optical scattering intensity distribution versus fiber orientation appear periodic, and with Fourier analysis this periodization could be used to precisely deduce fiber orientations of rough-sawn softwood and porous hardwood samples under investigation. A sensor consisting of one polarized laser and sixteen photodiode/polarization- analyzer assemblies has been proposed to measure fiber orientation.

We propose a new method for measuring a position of an endpoint of a metal cylinder in which a sinusoidal intensity distribution vibrating sinusoidally is used. The position of the endpoint is measured as a phase of a sinusoidally phase- modulated signal which is generated from a light diffracted from the endpoint. In order to extend the measurement range and measure a diameter of a metal cylinder two sinusoidal intensity distributions with two different periods of P₁equals100 micrometers and P₂equals98 micrometers are used. Cylinder diameters are exactly determined from the measurements for two endpoints of a cylinder using the two periods. Experimental results make it clear that the measurement error is less than 0.3 micrometers for a cylinder metal of 3885.2 micrometers diameter.

A contact probe mount with few nanometer repositioning capability for laser interferometric calibration of step- gauges and length bars has been attempted. Design is based on the autocollimetric capabilities of 0.01 sec. of arc capabilities to work out the deviation of the inductive probe which has to be moved up and downward for the positioning of the different facets of the gauge under calibration. A provisional mount has been arranged to study the repeatability and reproducibility of the design of the probe mount. The probe deviations thus observed can be used as correction factors or in improving the mount design to desired level of few nanometer accuracy. The methodology and the experimental setup used for the study is discussed in detail. A repeatability figure of 5 nm obtained with a manual mount conforms the design of the probe mount.

The system we propose uses two separate wavelengths to measure step height. Two laser diodes alternately modulated with a sinusoidal signal separate a like number of overlapping interference images detected by CCD camera, the phase map being obtained by a modulated LD. In this instance, the 1 micrometers step height was accurately detected.

Movement of optical patterns due to a slight lateral shift of wave-front in the nonlinear optical feedback system is investigated experimentally and theoretically. The dependence of the speed of patterns on the lateral shift is demonstrated experimentally and estimated by using the linear stability analysis. A small angle measurement using the nonlinear optical feedback system is discussed.

Moire method is an effective way to measure full field deformation. In this paper, the atomic force microscope scanning moire method and micro-moire interferometry method are proposed to determine the deformation in micro-area. The measurement principle and techniques are discussed. The two methods are applied to measure thermal deformation in a BGA (ball grid array) electronic package component. The shear strain (gamma) _xy at the solder site is determined. The experimental results including the adaptability of these two methods are compared and analyzed. The results show that AFM scanning moire and micro-moire interferometry methods are effective ways to measure the deformation in micro-area with high sensitivity.

Two fiber-optical methods for monitoring of stress processes in building structures under deformation are proposed. First method is based on using single-fiber double-mode interferometer as a sensor. It is shown that the single- fiber double-mode interferometer implanted into structure of a tested concrete unit allows to measure the unit structural deflection, absolute elongation and residual deformations in real time with accuracy not worse than 0.05 micrometers . It is also shown that the developed interferometric method allows to indicate a point of time of unit's crack initiation and also to estimate the crack opening displacement. Second method based on using single-fiber multimode as a sensor and photorefractive crystal allows to long-term monitor for dynamics of crack generation in real time.

A fiber Bragg grating (FBG) vibration sensor is constructed with two FBGs and an incoherent optical source. One FBG is used as a sensing element which intensity-modulates incident narrow-spectrum light, of which peak wavelength coincides with the slope in the FBG reflection spectrum curve. The narrow-spectrum light is produced by the other FBG in combination with amplified spontaneous emission output of an erbium doped fiber amplifier. Direct detection of the intensity-modulated light yields real time observation of the vibration. The developed sensor shows stable output in proportion to the vibration amplitude without using an optical isolator or fusion splicing, which are commonly used for the stabilization of FBG sensors with laser light as an optical source. Thermally stabilized operation of the sensor would be realized by keeping the temperature of both FBGs the same.

This paper describes a new quasi-distributed optical fiber strain sensor which is based on the coherent frequency- modulated continuous-wave (FMCW) reflectometry technique. The sensor comprises a laser diode and an unbalanced two- beam interferometer. Its test arm consists of a number of single-mode fibers, which act as the sensing fibers, with a mirror at the far end and mechanical splices as the connectors, as well as the reflectors. Theoretical analysis shows that the measuring resolution of the strain is inversely proportional to the gauge length of each sensing fiber. The strain variation of each sensing fiber can be measured by demodulating the phase shifts of the beat signals using a heterodyne signal processing system. To calibrate and verify the feasibility and accuracy of this sensing system, tensile and bending tests were carried out and their results were calculated and compared with the readings from strain gauge. Experimental results showed that this system is feasible and it has an excellent accuracy.

A novel differential double Bragg grating sensor for temperature-insensitive strain measurement is presented. The sensor consists of two identical weak measuring and reference gratings separated by some distance. The reference grating is placed inside the silica capillary that made it almost strain insensitive. The basic idea in differential double Bragg grating sensor is to measure the energy of the oscillating term in reflection spectrum of double Bragg grating structure. The normalized energy of the interference term depends on the pitch difference of two gratings and does not change when pitch variations of both gratings are equal with temperature variation. Therefore the normalized energy of the interference term can be used for the temperature-insensitive strain measurement.

A new type of Faraday effect optical current transformer has been developed which uses a square Flint (FR) glass block with dielectric-coated total reflection surfaces as the sensing element. Numerical calculation has shown that coating two dielectric layers of 45.59 nm-thick Ta₂O₅ and 448.35 nm-thick SiO₂ films on an FR glass surface gives rise to no-retardation total internal reflection for the 45 degree(s) incident angle light beam at (lambda) equals840 nm and has large tolerances for film thickness, wavelength and incident angle. A fiber-linked current transformer has been constructed and exhibited high performances including high isolation from surrounding currents and mechanical stability.

A novel structure of fiber optic sensor has been developed which is characterized by a short-length, different core- size fiber insertion in a fiber as a transmission network line. Two types of a macrobending sensor and an environment sensitive sensor are demonstrated. The macrobending sensor is expected in the use as multi-points (quasi-distributed) sensor. The environment sensitive sensor has the capability of interrogating with environmental conditions. The detailed structure and sensing principle of these new types of sensors are reported together with an experimental setup example arranged from the practical point of view and its attractive applications.

We present an optical sensor based on excitation of surface plasma waves in optical fiber structure consisting of a side-polished single-mode polarization-maintaining fiber and a metal overlayer. We describe two modes of operation of the sensor in which variations in the refractive index of the sample are determined by measuring changes in the transmitted optical power at a fixed wavelength (amplitude mode) and by measuring changes in the wavelength at which the resonant attenuation of the fiber mode occurs (spectral mode). We demonstrate that this design allows suppressing sensitivity of the sensor to deformation of the fiber yielding an improved stability and resolution.

We present a novel surface plasmon resonance (SPR) sensor based on serial organization of sensing channels and sequential spectral encoding of responses from sensing channels into an optical spectrum. This approach allows probing interfacial processes by surface plasmons of different field profiles which makes it possible to distinguish surface and bulk contributions to SPR sensor response. We illustrate this unique feature of the presented approach in a model biosensing experiment in which the detection of human chorigonadotropin (hCG) is compensated for background refractive index interference.

Low-pressure mercury lamps are commonly used for germicidal applications such as water and wastewater sterilization. The germicidal effect is due to the emission of light at 254 nm, which leads to the destruction of most waterborne bacteria. The Microwave Plasma UV Lamp (MPUVL) is a new technology for generating a high intensity UV light. A Fluorescent Optical Fiber based sensor is presented which is used for monitoring the output of a high power microwave UV light source and its control. This sensor is a fiber which has had its cladding removed and been coated with a phosphor doped polymer.

Different methods used to reduce speckle noise in speckle correlation fringes are only partially successful. Methods based on Fourier transform, such as low pass filtering or spectral subtraction image restoration have proven to be efficient to reduce speckle noise. Fourier Method, however, does not preserve details of the object. Thus errors are introduced when filtered image pattern is used to evaluate the phase distribution. To get rid of this problem, G. H. Kauffmann and G. E. Galizzi have implemented filtering by Daubechies (db) wavelet on computer generated TV holographic fringes. But it is observed that Daubechies wavelets are not much effective at edges in the speckle fringes. Symlet wavelets are linear phase filters and are effective from center to the edges of the speckle fringes. In this paper the experimental results of speckle noise reduction to improve the contrast of the speckle correlation fringes obtained by vibrating loudspeaker diaphragm and bracket of electric motor using filtering by Symlet wavelet is presented. The results show that filtering by Symlet wavelet is quite effective to enhance the contrast of the speckle correlation fringes. A large number of experiments are conducted on surfaces having different roughness. Experimentally it was found that to achieve optimum contrast enhancement of speckle correlation fringes, lower kernel median filter followed by Symlet is required for weakly diffused surfaces and higher kernel median filter followed by Symlet is required for strongly diffused surfaces.

A dynamic process of tensile experiment of austenitic stainless steel was observed by electronic speckle pattern interferometry (ESPI) which enables us to observe entire process of whole field deformation. In plastic deformation state, localized deformation appeared as concentrated correlation fringes in a narrow band, which run over the specimen repeatedly. Correspondingly, a stress curve took zigzag variation. In microscopic surface observation of fractured samples, martensite were found together with crashed grain. Increase of hardness was also confirmed. It means that strain induced martensitic transformation generates in part in heterogeneous structure of the material. These phenomena vary depending on carbon content and tensile speed. Correspondingly, propagating behavior of the band observed by ESPI, e.g. band propagating speed varies. It suggests that ESPI observation makes it possible to diagnose material degradation under in situ condition.

In this paper, a dual-beam in-plane sensitive electronic speckle pattern interferometry (ESPI) is applied to observe the degradation process of aluminum alloy plates under loading conditions. A quantitative phase analysis is performed using an addition-subtraction method.

In the present paper it will be shown how the introduction of a Fourier plane filter can create various types of common path interferometers for measuring changes in surface tilt or curvature of an object surface. This is obtained by placing a holographic optical element in the Fourier plane of a 4-f optical system. The interferometers are analyzed by using the paraxial approximation of the Huygens-Fresnel integral formalism, and the interferometer functions are given by a novel formalism using impulse response functions. Based on this technique, an interferometer for measuring dedicated changes in surface deflection is presented. This interferometer is insensitive to rigid surface rotations and displacements. The interferometer can be embedded in systems based on single point measurement of a time dependent deflection, i.e. vibrometers, as well as in full-field measurements such as electronic speckle interferometers.

The three-dimensional image formation can be managed by digital holography, where the holograms can be recorded by a CCD camera. As a law resolution of a CCD device, just a small angle between the object beam and the reference beam is allowed. This is the reason why the in-line phase- shifting digital holography is used to avoid the mentioned problem (the zero order beam can be neglected, too). In this paper it is proposed to use an arrangement of two reference beams recording the interference patterns of the object beam and the two reference beams by a CCD matrix. The phase distribution of the object wave can be recovered by a simple algorithm avoiding the uncertainty of the phase. The complex amplitude is used to reconstruct the image of the object by a computer applying the Fresnel transformation.

It is well known that the iterative stepwise quantization algorithm is very powerful for the optimization of amplitude digital Fourier transform holograms. We suggest a pre- iterative process to uniform the histogram distribution of the Fourier transform of the input image in order to reduce the reconstruction error of amplitude digital Fourier transform holograms. Simulation results show that the reconstruction error can be reduced much when our pre- iterative process is used in the iterative stepwise quantization algorithm.

Using digital phase shift holographic interferometry (DPSHI), the internal density distribution of water which is sealed in a cylindrical cell has been measured under the condition that one of the cylinder end walls is oscillated by a PZT-actuator, which is driven by high frequency: 20kHz. The density distributions concerned with three different end wall pressures have been visualized and analyzed by DPSHI. Carre algorithm is employed for phase interpolation to reproduce phase maps. The absolute density changes in the cell have been demonstrated. The results have indicated that DPSHI can allow us to measure small density changes in narrow space under high frequency oscillation.

Dynamic fluctuation of fluid surface induced by Benard- Marangoni convection was observed by means of the digital holography technique. A reconstructed phase obtained by the phase-shifting (in-line) method was compared with a result taken by the conventional (off-axis) manner. The complex amplitude of the object wave was first derived by the phase shifting of the reference beam and then subject to the Fresnel transform to obtain that at the object plane. In order to reduce ambient perturbation, a high-speed CCD camera (85 frames/s) was employed for the data acquisition. Surface height distribution and its temperature dependence were clearly quantified by this method.

Zero path-length difference interferometry is demonstrated using the filter response of unbalanced interferometer to the spontaneous/spontaneous beat noise spectrum of ASE source. The method is applicable to path-length differences ranging from few centimeters to several kilometers.

Velocity vector sensing by using fiber optic low coherent interferometer is proposed and demonstrated. The direction and absolute value of the flow velocity can be measured from a peak position of a correlation between two backscattering lights from probing points on the x-, y-, and z-axis in flow.

Amplitude-division two-beam interferometry performed with temporally incoherent light (such as white light, i.e. the path difference is larger than the coherence length) is used to multiplex signals, and applied to the multiplexing of sensors, and for distance measurements. The detection is based on the use of a receiving interferometer tuned to approximately the same path difference. An alternative way to detect path differences in Low Coherent Intensity, by analyzing the output intensity fluctuations with a radio frequency spectrum analyzer (RFSA) is proposed. This is suitable for very long path differences. Experiments have been performed with different lengths from meter to some kilometer of single-mode optical fiber, in a Mach-Zehnder and Michelson configuration.

The low-coherence interferometric technique is proposed for the in-situ measurement of the refractive index of dispersive samples with high accuracy. A tandem configuration of a Michelson interferometer and a triangular interferometer is used to compensate for the chirping effect which results from the broad spectrum of the light source. Thick samples can be successfully measured with the low- coherence interferometer, therefore the relative accuracy of the refractive index can be improved.

A closed loop phase shifting Fizeau-type interferometer is constructed by using the direct frequency modulation (FM) of a laser diode. The interferometer is servo controlled fully in the phase domain where optical phases are detected by a two-frequency optical heterodyne method. Detailed study on stabilization of the interferometer under feedback control is conducted both experimentally and theoretically. The interferometer showed a good stabilization against the applied vibration up to 200 Hz. The profile measurement of a mirror surface was conducted by the phase shifting analysis algorithm and a good measurement reproducibility of (lambda) /60 in the root mean square value was obtained for 10 times measurements in a period of 20 min.

This paper describes the compulsorily phase locked differential interferometer using orthogonally polarized light source of a modulated LD with high extinction ratio for reducing non-linearity of the interferometer due to polarization cross-talk. The current modulated LD are used as a light source for making the interferometer a compact and for scanning phase of the interferometer. A Wollaston prism of high extinction ratio (50 dB) is used as a beams combiner of the polarizing beams for making the polarization cross-talk very small. In one light source the polarized output beams are on the same propagation axis. In the other light source the polarized output beams have small crossing angle (2.5 mrad approximately equal to 10 mrad) for excluding completely non-linearity of the interferometer due to polarization cross-talk. It is confirmed that the cross- talk components of these developed light sources are very small compared with those of the conventional orthogonally polarized light source using polarizing beam splitters. Using jets of a gas mixture of nitrogen and ethylene, it was demonstrated that the compulsorily phase locked differential interferometer is useful to detect photothermal effect of photothermal velocimeter in turbulent flow.

A self-reference method (SRM) is proposed to realize high precision fringe analysis for phase-shifting interferometry when translation and tilt errors exist in phase shifters. In this method, arbitrary pixel-dependent phase shifts including those caused by tilt are directly estimated from a single interferogram by the Fourier transform method without using any extra reference mirror. The obtained phase shifts are then used to reconstruct the original wave front according to the algorithm of the proposed self-reference method. Computer simulations demonstrate the feasibility of the proposed method. Precision of shifted phases and tilts estimation is also evaluated, and some error sources are analyzed. It is shown that the self-reference 3-step method can give better accuracy than that of the popular 5-step method even when the tilt error exists in the reference surface.

We present a new type of phase-shifting microscope that enables us to quantitatively measure the phase distribution of a transparent microscopic object. In this microscope, a Fresnel's biprism is used to make the object wave and a reference wave to interfere. The biprism is laterally moved by a piezoelectric transducer to produce the phase shift between the two waves required for phase extraction using the phase shifting technique. The diffraction caused by the vertex of the biprism is avoided by placing a thin wire at the center position of an intermediate image plane. The technique described here can be easily applied to an ordinary optical microscope, moreover, this technique can also be applied to an electron holographic interference microscope using an electron biprism. Experimental results for measuring the refractive index distribution of an optical waveguide are presented.

In the present paper we consider an approach to automatically correct aberrations induced by atmosphere in laser communication signals by means of dynamic holograms. The main requirements to a dynamic holographic material are specified. The most appropriate materials and their parameters are listed.

A novel temperature sensor with high sensitivity using a long-period fiber grating has been proposed, fabricated and evaluated. Temperatures are detected by shifts of resonance wavelength of the transmission spectrum. In the experiment, the temperature sensor was able to measure temperatures from 5 degree(s)C through 50 degree(s)C.

In this paper, we analyze and propose a non-uniform transmission based ramp chirp grating which can give maximum negative dispersion profile over broadband wavelength range. Coupled mode theory is used for obtaining quantitative information about the delay spectral dependence of the grating structure. A matrix method is used for analyzing the grating characteristics. For a grating length of 25 m, the grating can give negative dispersion of 266 ps/nm. When the grating is inserted after 16.07 km in line with the existing fiber optic link, the maximum average compensated dispersion lies within +/- 1.0 ps/nm-km over 1530-nm - 1560-nm wavelength range.

A novel wavelength-tunable add/drop multiplexer is designed and proposed to be used as a signal selector in dense wavelength-division multiplexing systems, which is based on four identical long-period gratings assembled on four same structured piezoelectric ceramic fiber stretchers, and their operation of wavelength-selective coupling modes. By contrast to fiber Bragg gratings used in add/drop multiplexer, long-period gratings could be specifically designed to operate in transmission mode.

The transmission characteristics of phase-shifted long- period gratings are simulated theoretically by a combination of couple-mode theory and fundamental-matrix method. It is suggested that a phase-shifted LPG device cascaded with another normal LPG can be used to flatten the gain spectrum of an erbium-doped fiber amplifier with all three gain peaks. The results of simulations have shown that a broadband amplifier with peak-to-peak 0.7 dB gain variation over 36 nm can be practically realized. It proves that such a gain-flattening fiber filter is indeed plausible, and has a potential application in gain-flattening in dense wavelength division multiplexing telecommunication systems.

Quantum confined nanostructures are very important because of their application towards optoelectronic devices. Commercial colored glass filters, which have large semiconductor particles, are being used to manufacture nanocrystals by suitable heat treatments. The progress in this area has been hampered by high size dispersion of these dots in the glass matrix which leads to reduction in higher order susceptibility thereby reducing non-linearity. In the present paper attempt has been made to theoretically model the temperature profiles of a laser irradiated CdS doped Borosilicate sample. Laser being used has a beam diameter of 1.5 mm and energy for 10 nsec pulse is 10 mJ. Two different particle radii of 5 nm and 10 nm have been considered. It is found that larger particles reach higher temperatures for the same pulse characteristics. This is because smaller particles have larger surface to volume ratio and hence dissipates out heat faster to the surrounding. Hence bigger particles will reach dissolution temperature faster than smaller particle and particle beyond a certain size should dissolve in the glass matrix when a sample is heat treated by laser. This could lead to a reduction in size dispersion of the nanocrystals. Also photodarkening effect found in semiconductor doped glasses is a big handicap for practical application of these materials in fast optical switching and non-linear optical devices. Photodarkening effect has been established to be a photochemical effect and it is important to study the temperature profiles around a particle since it will effect the impurity migration.

Up-conversion lasing of a new random medium, which is composed of thulium-ion-doped fluorozirconate glass particles and TiO₂ powders, is demonstrated. In this medium, it is expected that the near-infrared excitation light will deeply penetrate into the random medium to induce multiphoton excitation processes, while the emission in the visible wavelength region will be confined in small volumes by the strong multiple light scattering. When the power of the excitation light was increased, sharp emission peaks appeared and their peak intensities increased relative to the background spontaneous emission. The excitation power dependence clearly shows the lasing threshold.

A multichannel optical spectrum slicer (MOSS) using a rod of birefringence TiO₂ crystal has been developed to provide a series of required spectral components for evaluating as well as examining optical components and devices employed for the DWDM transmission system. The MOSS works as a frequency tunable, multichanneled filter as well as a generator for reference multichanneled frequencies.

The novel photonic encoder and decoder configurations for the optical code division multiplexing (OCDM) are proposed. The angle-multiplexed hologram in the spectral holographic system is used for generating coded waveforms and for correlation of waveforms. The performance analysis from the spectral efficiency point of view is presented.

This paper describes a newly designed multipoint process monitoring system based on an acousto-optic tunable filter. In order to prove the feasibility of the suggested multipoint monitoring system for use in the NIR spectral region, some experiments were carried out in the visible range. The multipoint process monitoring system consists of an AOTF device for wavelength selecting, a CCD imaging sensor, and a specially designed in-line type of optical fiber probe. Unlike an FTS (Fourier Transform Spectrometry) based monitoring system, an AOTF has no moving parts, and it can be rapidly tuned to any wavelength in its operating range within microseconds. Thus, the AOTF is advantageous in terms of faster spectral imaging capability and rigidity required for industrial monitoring environment. Also, Fourier Transform Spectrometry experiments were conducted for comparison with the AOTF based monitoring system. In the current feasibility evaluation, an enhanced optical fiber probe with 3 monitoring points was used. However, the number of monitoring points can be easily expanded to dozens more points as required.

Methods for the physical analysis of large-scale 3D lightwave circuits (LWCs) are reviewed and the crucial points of the ongoing work are made transparent and discussed.

A new technique to improve the accuracy of the infrared radiation thermometry is presented. We combine the real time emissivity compensation with the three-colored technique proposed to suppress the effect of stray lights. We first examined the effectiveness of the three-colored technique and found that the measurement error caused by stray lights is decreased from 150 degree(s)C to 10 degree(s)C for the sample of 650 degree(s)C.

This paper describes a novel refractive index sensor with a guided-mode resonant grating (GMRG) filter. The GMRG filter is a narrowband wavelength reflection filter. The incident light is reflected at a resonance condition of incident angle and wavelength. When the grating filter is covered by a liquid to be tested, the resonant condition depends upon its refractive index. The refractive index of the liquid can be determined from the resonance angle for a known wavelength. Since a full-half width of incident angle for the resonance is very narrow (less than 0.1 degree(s)), a high resolution is expected. We designed the GMRG filters for the refractive index sensor. And the resonance angle of incidence was investigated experimentally for the mixture of water and ethyl alcohol.

Nonlinear optical properties of cover glass/ZnS-SiO₂(130nm)/AgO_x(15nm)/ZnS- SiO₂(40nm) is studied by using a focused continuous-wave (CW) He-Ne laser ((lambda) equals632.8 nm) and a pulse laser ((lambda) equals532 nm, pulse width 0.7 ns, repetition rate 15.79 kHz) with a confocal Z-scan system. The transmission confocal Z-scan shows that the sample undergoes a phase transition at different incident intensities when the light source is changed. High reflectance happens at the focusing on AgOx film. The phase transition of the sample at higher incident laser power is due to silver oxide dissociating by the laser heating process.

The near-field recording mechanism of the super resolution near-field structure, glass/ZnS-SiO₂/AgO_x/ZnS-SiO₂, has been studied experimentally. Near-field optical effects of the glass/ZnS-SiO₂/AgO_x/ZnS-SiO₂ have been observed by a tapping mode tuning-fork near-field scanning optical microscope (TMTF-NSOM) on the transmitting light spot. Laser-excited surface plasmon at the interfaces of AgO_x/ZnS-SiO₂ thin film was detected by this technique. Results showed that the transmitting focused light through the AgO_x type super resolution near-field structure consists of a propagating term and an evanescent one resulted from the localized surface plasmon of the AgO_x thin film. A strong enhancement of the near-field intensity and the dynamic localized enhancement of the transmitting focused light were observed as well.

A photon correlation LDA system for the simultaneous measurement of sub-micrometer particle size and velocity is introduced. Following the results of Monte Carlo simulations it is shown that the FFT of the auto-correlation function of the detected scattered intensity contains the information on particle size. Experimental results on polystiren latex particles of 100 nanometer size are discussed.

This paper describes the development of an optical system that can simultaneously generate an interferogram and a shadowgraph of a refractive index field (in this case, a compressible fluid flow). Such a combination allows one to record both the density and its second derivative OF THE SAME OBJECT AT THE SAME TIME. This can be achieved by splitting the object beam of a holographic interferometer before superimposing it with the reference beam. One half of this beam forms the hologram together with the reference beam, while the other is led into an imaging unit that generates an image of a plane that is located either before or behind the test object (the so-called shadow plane). This arrangement allows one to generate simultaneously two pictures, which provide more reliable quantitative and qualitative data about the investigated flow than each of the visualizations alone.

In this paper we have investigated the utility of Lau phase interferometer with white light source and circular gratings to measure temperature and temperature profile of an axisymmetric flame. In Lau phase interferometer the two gratings are separated by infinite distance. The third grating is placed at a distance Z equals n.p²(lambda) , (where n is an integer, d is the pitch of the grating and (lambda) is the wavelength of the white light source). The sensitivity of the system is determined by the pitch 'p' of the grating and the distance Z between the gratings. If the distance Z between the two gratings is increased to enhance the sensitivity, the accuracy of measurement is reduced because of the reduction in the fringe contrast. In white light Lau phase interferometer the fringe contrast can be improved by optimizing the self-image plane and the pitch of the grating. From the recorded interferogram the angle of deflection ((phi) ) is measured and temperature at a different point of the flame is calculated. The temperature measured using Lau phase interferometer is in good agreement with the temperature measured by thermocouple and dataloger. Details of the theoretical analysis and experimental results are presented.

A method to measure the phase distribution of a light wave by compensating its wavefront distortion with a liquid crystal spatial light phase modulator (LC-SLPM) is improved by utilizing the double path mode of LC-SLPM. The characteristics of the double path LC-SLPM is examined experimentally, and it is verified that this device is effective for adaptive optics use because it is able to modulate the light phase over 2(pi) rad without causing significant amount of intensity modulation.

A new method for joint-transform correlator (JTC) is presented in which complex amplitudes of joint power spectrum (JPS) of two inputs are measured by the six-step phase-shifting interferometry with a wavelength-shifted laser diode (LD). A phase calculation is immune to the changes in LD power. A joint-transform phase correlator JTPC) is demonstrated with a single centered correlation by the numerical Fourier transformation of a measured phase in an on-axis JPS. Multiple-object recognition by a JTPC is performed to eliminate the correlation between input targets. The experimental results with a JTPC are shown, exhibiting sharp correlation peak.

In order to overcome the limitation of the image processing speed of the conventional video camera system, we have designed and constructed a column parallel vision (CPV) system. The CPV system realizes an intelligent and general purpose image processing capability with higher frame rate within 1 millisecond (i.e. 1000 frames/s). The system mainly consists of three parts; a sensing unit, a parallel processing unit and a control unit. The sensing unit has a 128x128 photodiode (PD) array, 128-column parallel amplifier array and A/D converter array to achieve high-speed frame rate and has been integrated in a CMOS chip. The parallel processing unit is composed of fully 128x128 processing elements (PEs) to perform a real-time image processing. The control unit has functions of PD/PE control and interface to the host computer. We have confirmed that the CPV system can process general image processing functions within a few ten microseconds. We have also demonstrated that the system can be worked as a tracking system with high-speed feedback loop and have evaluated the accuracy of the position calculation for the desired target.

The basic problem associated with aspheric testing without the use of null optics is to obtain increased measurement range while maintaining the required measurement accuracy. Typically, the introduction of a custom-designed and fabricated null corrector has allowed the problem of aspheric testing to be reduced to that of spherical testing. Shack-Hartmann wavefront sensors have been used for adaptive optics, but have seen little application in optical metrology. We will discuss the use of a Shack-Hartmann wavefront sensor as a means of directly testing wavefronts with large aspheric departures. The Shack-Hartmann sensor provides interesting tradeoffs between measurement range, accuracy and spatial resolution. We will discuss the advantages and disadvantages of the Shack-Hartmann wavefront sensor over more conventional metrology tests. The implementation of a Shack-Hartmann wavefront sensor for aspheric testing will be shown.

A novel Fourier-transform imaging spectrometer based on Savart polariscope is presented. The novelty of this work comes from slitless in this instrument, which means high throughput. The effect on the interferogram due to the pixel size is analyzed. The principle and the system configuration are described. Several preliminary experimental results are shown.

In the given paper principles of organization of neural-like system consisting of a matrix of photoelectric cells are represented. The practical realization of this system allows to obtain a parallel processing of an optical information for environmental physical field monitoring . A computer model of the feed-forward neural network with the hidden layer is developed to reconstruct physical field investigated by the fiber optic measuring system. The Gaussian distributions of some physical quantity are selected as learning patterns. Neural network is learned by error back-propagation using the conjugate gradient and coordinate descent minimization of deviation. Learned neural network reconstructs the two-dimensional scalar physical field with distribution having one or two Gaussian peaks.

We are first to demonstrate the underwater lidar imaging (UWLI) in such a 3 m short water tank with highly turbid water successfully, and show the range-gated phenomenon in water much more clearly based on our newly designed serial targets. The target set comprises a series of three bar test targets (five in total), which are set at intervals of 22.5 cm roughly along the laser illumination direction since the light speed in water is 22.5 cm/ns. We synchronize precisely (approximately 0.5 ns) the UWLI system to range-gate on the targets which we want to capture their images, and to range- gate out the targets which we do not want their images. The attenuation coefficients in water are 1.0/m and 2.3/m (extremely turbid). Compared with non-gated case, the most distinct difference between the gated images and non-gated images in turbid water is that the nearer the target is located, the clearer its image is on the non-gated photos, but for the gated case the situation will be inverted completely when the delay time is adjusted suitably; that is, the image of the farther target could be much clearer than the image of the nearer target even in very turbid water.

In this paper, fiber optic spectroscopy is developed to detect and quantify recombinant green (EGFP) and red (DsRED) fluorescent proteins in vitro and in vivo. The bacterial expression vectors carrying the coding regions of EGFP and DsRED were introduced into Escherichia coli host cells and fluorescent proteins were produced following induction with IPTG. Soluble EGFP and DsRED proteins were isolated from lysed bacterial cells and serially diluted for quantitative analysis by fiber optic spectroscopy. Fluorescence at the appropriate emission wavelengths could be detected up to 64X dilution for EGFP and 40X dilution for DsRED. To determine the capability of spectroscopy detection in vivo, transgenic potato hairy roots expressing EGFP and DsRED were regenerated. This was achieved by cloning the EGFP and DsRED genes into the plant binary vector, pTMV35S, to create the recombinant vectors pGLOWGreen and pGLOWRed. These latter binary vectors were introduced into Agrobacterium rhizogenes strain A4T. Infection of potato cells with transformed agrobacteria was used to insert the fluorescent protein genes into the potato genome. Genetically modified potato cells were then regenerated into hairy roots. A panel of transformed hairy roots expressing varying levels of fluorescent proteins was selected by fluorescence microscopy. We are now assessing the capability of spectroscopic detection system for in vivo quantification of green and red fluorescence levels in transformed roots.

We present a dual-channel surface plasmon resonance (SPR) biosensor and demonstrate its applicability to detection of foodborne pathogens such as Staphylococcal enterotoxin B (SEB). Experimental results indicate that the SPR biosensor can detect SEB at very low concentrations: 5 ng/ml in pure samples directly, 0.5 ng/ml in both pure samples and in milk using a sandwich assay.

In a previous paper, we described the use of fiber optic spectrophotometry as a non-destructive and sensitive method to detect early symptoms of plant nutrient deficiency. We report further developments of our work on Brassica chinensis var parachinensis (Bailey) showing reproducibility of our data collected at a different seasonal period. Plants at the mid-log growth phase were subjected to nutrient stress by transferring them to nitrate- and calcium- deficient nutrient solution in a standing aerated hydroponic system. After tracking changes in leaf reflectance by FOSpectr for nine days, the plants were returned to complete nutrient solution and their recovery was monitored for a further nine days. The responses of nutrient stressed plants were compared with those grown under complete nutrient solution over the 18-day trial period. We also compared the sensitivity of FOSpectr detection against plant growth measurements vis-a-vis average leaf number and leaf width and show that the former method gave an indication of nutrient stress much earlier than the latter. In addition, this work indicated that while normal and nutrient-stressed plants could not be distinguished within the first 7 days by tracking plant growth indicators, stressed plants did show a clear decline in average leaf number and leaf width in later stages of growth even after the plants were returned to complete nutrient solution. The results further reinforce the need for early detection of nutrient stress, as late remedial action could not reverse the loss in plant growth in later stages of plant development.

By employing an optoelectronic phase shifter as a delay-time controller to replace the conventional opto-mechanic delay line, a delay-line-free high-speed electro-optic sampling (EOS) System is proposed as a novel and unique module which overcomes the drawbacks of conventional electro-optic sampling system, such as the measuring distortion caused by misalignment of probe beam and difficulty in sampling of free-running high-speed transients. Versatile configurations of PLL circuits suitable for modifying as an ODTC in the EOS system are interpreted and the performance of the ODTC such as maximum tuning range, linearity, speed, and resolution are determined. The waveform sampling of the free-running sinusoidal microwave signal, the digital signal output from a frequency divider (or prescaler), and the electrical pulse generated by the comb generator are demonstrated.

Planar switching matrices of parallel waveguides (WGs) have reduced loss due to the absence of tapering but require some confinement of wave propagation reported from Kerr nonlinearities (NL). Parallel switching matrices are fed by the multiple splitting of the input WGs, an appropriate network model is the parallel version of the Spanke-Benes (PSB) network and the reduction of the number of stages (NSs) below N (for N i/o) is analyzed. However, in the parallel case, regarding WGs and SB networks, the location of switches can no longer be fixed but must be a moving location (ML). From the several parallel paths through the PSB network the shortest path is chosen either at the end by path selection switches (PS-SWs) or at the beginning of the switching matrix, respectively. It turns out that the reduction of NS of the switching matrix and in turn the saving of the number of switches (NSWs) is compensated by the number of PS-SWs at the end or at the beginning of the matrix. The replacement of the PS-SWs by combiners at the output (i) restores the energy balance but (ii) causes phase mismatch (iii) provides redundant paths (iv) restricts the overall NS to the NS of the SB network for each copy but (v) improves the nonblocking (NB) characteristic. The routing of the switching matrices and their optical implementation is also briefly discussed.

A series of structurally varied organic molecular switches have been prepared and their switching behavior examined. For thermally active compounds, the switching rates have been extracted from variable temperature NMR experiments and simulation studies. Additionally, chromophores have been incorporated for optical activation of thermally stable switches. Supramolecular architectures for constructing optoelectronic devices are also described.

In this paper, different structures of high-speed infrared (IR) sensors based on amorphous silicon germanium and amorphous silicon hetero-structures have been successfully developed on crystalline silicon substrates. Experimental results of these developed structures exhibit a superior device performance to that of a traditional pin amorphous photo-sensor prepared on a glass substrate, especially significant improvements in the rise time from 465 (microsecond(s) ) to 195 (microsecond(s) ), and the dark current from 50 ((mu) A) to 3.3 ((mu) A) for 5 (V) reverse bias.

In this paper, to suppress dark current of high temperature (beta) -SiC/Si optoelectronic device with a porous substrate has been studied. A pin structure was used to demonstrate the applicability. Experimental results show a twelve-fold improvement in optical gain at 200 degree(s)C operating temperature for the sample prepared on the porous silicon substrate as compared to the sample prepared on the silicon substrate, respectively. The improvement is attributed to the suppression of dark current by the high resistivity and flexibility of the porous substrate. A (beta) -SiC/Si optoelectronic device was fabricated both on porous silicon substrate and conventional silicon substrate, respectively. Experimental results show the optical current ratio can be improved up to 400% at room temperature and 3000% at 200 degree(s)C operating temperature, respectively, with the porous silicon substrate.

Impulse response of a metal-semiconductor-metal photodiode to a short laser pulse is computed and discussed in terms of the distribution of photogenerated carriers and electric fields. We show that the heterobarrier structure in the light absorbing region greatly enhances the response speed of InP/GaInAs MSM detector.

In this paper, a new electro-chromic device (ECD) is developed by tungsten oxide (WO₃) thin film integrated with a-Si_1-xGe_x:H pin photodetector. With the addition of the palladium (Pd) film to ionize hydrogen gas, the WO₃ thin film will react with hydrogen ion and transfer from transparency to blue color. This color change will degrade the absorption of light with wavelength larger than blue color. First, we determine the most suitable condition (by increasing the partial oxygen pressure) to produce a-WO_x films, thus offering a good electro- chromic performance for opto-switching applications. Then, the photo current generated by a-Si_1-xGe_x:H pin photodetector will be lowered down, thus detecting the existing of hydrogen gas. Especially, the WO₃-pin hydrogen sensor also shows highly selectivity with hydrogen gas to separate from CO and C₂H₅OH gases.

The paper presents novel concepts of batch fabrication of micro-ball lens array technology integrated on the silicon based wafer by low temperature wafer bonding by which can improve appropriate distance of optical fiber coupling. The silicon based coupling platform consists of the self-parking framework, micro-ball lens array, and precision platform for optical fiber coupling purpose. The structure of optical platform is able to improve distance of between fiber and micro-ball lens and increase coupling efficiency. The micro- ball lens array is batch fabricated by polymeric material and melting photoresist through low temperature wafer bonding. Then batch assembly onto each other flat-topped mesa that adjoins to the v-groove. The corner compensation offers a method to fabricate self-parking framework and flat-topped mesa in the intersection of two v-grooves. This fabrication process not only provides accurate coupling distance between fibers and micro-ball lens but also reduces micro-assembly cost.

Analytical theory of plane electromagnetic wave reflection from a layer or half-space of a particulate photonic crystal is introduced. The photonic (artificial) crystal is formed by small complex-shaped dielectric or metallic inclusions arranged in the nodes of a regular three-dimensional lattice with parallelepipedal elementary cell of general kind. The background medium is assumed to be an isotropic dielectric. The dipole model and the local field approach are used for description of electromagnetic interaction between inclusions. Frequency dependent polarizabilities are used for description of inclusions polarization. The interaction between adjacent layers is considered using the Floquet representation including evanescent modes. Using an analytical theory of dispersion for the crystals under consideration it becomes possible to make predictions for dipole moments distribution deep inside the layer. Additional corrections for distribution in the surface layers and amplitudes of predicted modes have been found numerically from a linear system of equation. This method needs much less computational time comparing with the same method without prediction of distribution and can be applied for calculation of reflection coefficient for much thicker layers or for a half space.

Many researchers have investigated the interaction of femtosecond laser pulses with a wide variety of materials. The structural modifications both on the surface and inside the bulk of transparent materials have been demonstrated. When femtosecond laser pulses are focused into glasses with a high numerical aperture objective, voids are formed. We report first observation that a bubble, which is called void moves under irradiation of femtosecond laser pulses inside silica glass and calcium fluoride. In situ observation reveals that the void moves towards incident direction of laser pulses as long as 5 micron by successive laser pulses without any mechanical translations.

Refractive-index change is induced by a self-trapped filament of ultrashort laser pulses in a wide variety of glasses. We investigated the dependence of refractive-index change on polarization state of incident ultrashort laser pulses in silica glass. We fabricated birefringent structures and estimated the refractive-index change.

Ceramic is an important material for electrical engineering fields because it has high creep, chemical, and temperature resistances. MEMS technology sometimes needs transparency and chemical resistance, so glass is often used. As the system size becomes smaller and smaller, however, it is impossible to machine such materials by conventional methods because they are hard and brittle. Some unconventional methods are suitable for non-conducting ceramic materials regardless of their properties of hardness, toughness, and brittleness. Electrochemical discharge machining (ECDM) is one of the unconventional methods for ceramic materials. However, ECDM usually requires tools fabricated by other machining. As the machining size becomes smaller, the coordinate system of the tool tip can be easily changed when we fix or replace the tools. This paper proposes a new machining system; the system has two fabrication modes. It makes a tungsten tool by electrochemical process (ECP), and then, ceramic materials are machined by ECDM with this tool. These two machining systems can be easily transformed from only one system by the regulation of the concentration of the electrolyte and the electric power controller. We illustrate and analyze some experimental results of the machining of tungsten tools and ceramic holes which have various geometric shapes.

A tapping mode atomic force microscopy (AFM)/scanning tunneling microscopy (STM) system using a non-optical tuning fork force sensing method has been developed for the scanning probe lithography. In comparisons with the nanolithography done by AFM with the conductive cantilever tip, our method has the following advantages. (1) It has longer tapered length STM tip and smaller half cone angle to perform the nanometer scale patterning with high aspect ratio. (2) Its low cost tungsten or Pt/Ir STM tip can be easily fabricated and attached to our AFM force sensing tuning fork. (3) It can be easily adapted to large-scale parallel processing because of the all-electric force sensing methods. Nanostructures with high aspect ratios and large depths have been successfully performed on the silicon surface by using our AFM/STM nanopatterning system followed by the differential etching process. Lines with different widths and matrices of dots with various diameters were demonstrated for potential applications.

We present a grating array illuminator that serves at two different wavelengths. The grating was designed by simulated annealing method and drawn in photoresist by direct laser lithography that we have developed on optical disk mastering technology. Upon grating reconstruction with two chosen wavelengths, 1064 and 532 nm, from Nd:YAG lasers, two arrays of 9 split beams with the same pitch were reconstructed. The illuminator performance was found rather sensitive to profile errors, which was supported by computer analysis.

A model for power distribution from a series of radiative taps on multimode optical fibers is presented. This model can be used for designing and packaging tapped fiber based optical devices and subsystems: distributed sensors, delay lines, signal processors, add-drop multiplexers, and array illuminators. Case studies on analyzing a distributed fiber optic pressure sensor and designing an array illuminator with an equal amount of power from each tap are discussed.

The conventional iterative Fourier transform algorithm proposed by Fienup which reconstructs the phase from the modulus is improved. Stagnation from which the conventional algorithm often suffers does not occur in the improved algorithm.

The Laguerre-Gaussian (LG) beam is an optical beam with a phase singularity that propagates along its axis. We have previously reported the fabrication of blazed transmission phase holograms to generate beams with phase singularities. A common problem encountered in the generation of a phase singularity with high charge is that the singularity tends to split into m individual charge 1 singularities, where m is the charge of the original singularity. We have found through numerical simulation that astigmatic aberration can cause a higher-charge phase singularity to split. We have also found that strong astigmatic aberrations make the resulting beam close to a Hermite-Gaussian beam rather than an LG beam. Experimental investigation of these phenomena agree with the numerical simulation.

The bluish appearance of veins in the skin tissue was experimentally investigated by in vivo and in vitro measurements. The color of skin surface including veins inside was evaluated by spectrophotometry and color analysis in the CIEXYZ and CIELAB colorimetric systems. The bluish appearance was successfully interpreted by the dominant wavelength and the color difference. Results for in vitro experiments showed that the degree of bluish appearance depends on the depth and diameter of blood vessels.

The purpose of this study is to investigate spatial coherence of superluminescent diode (SLD). In order to measure the spatial coherence, we use an interferometer with double slit. The relation between visibility of the fringe and the diffraction length are reported. Furthermore, difference in spatial coherence between SLD and LED is discussed.

This study concerns the automatic high precision beam collimation system using the Talbot interferometry. When the collimation beam is obtained placed point-source of light in focal position of the collimation lens, the defocus value is calculated from a moire fringe width in the Talbot interferometry using only two grating. With the advance of collimation, the moire fringe cannot be confirmed. Using the movement of moire fringe when one of grating shifts, the expanded moire fringe width is measured high precisely from the phase difference of intensity change of two detecting points, using peak position of the cross-correlation coefficient. With the result of the defocus value, the collimator lens is positioned by motor controller.

A surface profiler incorporating a feedback controller that eliminates external disturbances is proposed and demonstrated. Its overall performance is dependent upon the frequency response of the feedback loop. The frequency of modulating signal strongly influences response of the feedback controller. When using an integrating bucket method, however, the CCD camera must be operated at the NTSC-approved modulating frequency. Our technique uses electronic shutter equipped CCD camera. The shutter function enables us to apply high-speed sinusoidal phase modulation to the conventional integrating bucket method under the NTSC standards.

This study suggests an optical fault-tolerant system using all-optical sensing and feedback circuits with photorefractive crystals. The first example is a fault- tolerant system in which the system independently detects a cutoff of the optical transmission line and converts its routing to the backup line. Next, while practical application of holographic optical memory is currently being developed, under proposing system, the memory system automatically detects the loss of information (dropout) in optical memory, and reloads and eventually restores the corresponding data from the backup memory.

The analysis of measurement errors of distance up to a mirror surface by laser triangulation is given. We consider the two types of sensors: with output plane, orthogonal to the optical axis, and with tilted one (corresponding to the Scheimpflug principle). The conditions of Scheimpflug principle applicability for mirror surface testing are determined. We have shown that at the certain ratio between parameters of optical system of the sensor and the probing light beam, the sensor with orthogonal plane of photoregistration can provide smaller level of measurement errors, than sensor with tilted plane, despite the presence of defocusing.

Photorefractive polymers doped azo-dye with electric field poling and photoinduced poling whose wavelength is 633 nm using four-wave mixing and two-beam coupling experiment at 780 nm are investigated. An increase of diffraction efficiency by the effect of photoinduced poling through photoisomerization in photorefractive polymers is demonstrated. And the diffraction efficiency depends on the intensity of photoinduced poling beam, and it has peak value.

The polarization state of light-gated phase conjugate beam in a methyl-orange doped polyvinyl alcohol film was investigated for various polarization configurations of pump and probe beams. Circularly polarized light emitted by an argon-ion laser at 515 nm was used as a gating beam for uniformly exciting randomly oriented methyl-orange dyes, and a krypton-ion laser light at 647 nm was used for degenerate four-wave mixing process. Experimental results agreed well with theoretical results, which obtained by assuming that the methyl-orange doped polyvinyl alcohol file is optically isotropic. From the comparison between experimental and theoretical results, we obtained the tensor of nonlinear optical susceptibility (chi) ₁₂₂₁equals0 at a wavelength of 647 nm in the presence of the gating light.

Previously we developed the filter bank method that enables to extract from a defocused image the information on the amount of defocus. In this paper, we apply this method to a defocused image with extremely low intensity detectable only with a photon counting camera. Experimental results show that the information of the defocus amount can be extracted from such a blurred photon image and simultaneously the original object is successfully restored.

The generation theory of interference fringes patterns considering the aberration of the focusing lens is proposed in a position-sensing grating interferometer for a specular object. The proposed theory is based on the assumption that the deformation of the wavefront passing the interferometer is limited by the symmetry of the interferometer and that the wavefront can be expressed by Zernike polynomials. The simulation and experimental results are presented. The interference fringes pattern of the form of a barrel and a spool were obtained by the simulation. The experimental results agreed well with the simulation results.

A photoacoustic and photothermal deflection imaging apparatus was fabricated using linear-motor-driven slide stages as the scanning tool. It achieved both high resolution scanning (0.1 micrometers step), fast scan (40 mm/sec) and random access. In gas microphone photoacoustic microscope (PAM) operation, the reduction of acoustic noise about 30 dB compared that with pulse-motor-driven pulse stages was achieved. Photothermal defection microscope (PTM) using a high-resolution position sensitive device realized both comparable resolution of thermal image as that of PAM and the open-air environment for nondestructive inspection of solid specimen in common operating software as PAM. Applications of the PAM and PTM to nondestructive evaluation of both surface and undersurface defects of the solid specimens including semiconductor microdevices and a simulated subsurface defect are also demonstrated. Achieved resolution of the thermal images of an integrated circuit fabricated on a silicon substrate obtained using both PAM and PTM was up to 8-12 micrometers .

The SHG interference microscope was applied to the observation of the ferroelectric 180 degree(s) domain structure along the axial direction in a y-cut MgO:LiNbO₃. Using four different SHG interference images with phase difference of 0, (pi) , +(pi) /2, and -(pi) /2, the special functions of the SHG intensities were calculated in the so- called (eta) -plane, from which the 3D domain structure was successfully obtained.

The imaging of the simulated surface-subsurface combined defect using photoacoustic microscope has been demonstrated. Simulated surface and subsurface defects are fabricated independently such that the former was drilled on a pure aluminum plate whereas the latter was machined with end mill. Specimen with subsurface defect alone was also carried out. The photoacoustic image obtained clearly showed the location and the size of both subsurface defect and the surface-subsurface combined defect. The photoacoustic method is useful for detection of the combined defect which is difficult to detect with present NDE techniques.

The miniature fiber optic Fabry-Perot pressure sensor with a silicon diaphragm was developed for medical applications. The configuration of this sensor was a 1-mm long fiber optic Fabry-Perot interferometer bonded to an 80 micrometers -thick diaphragm. The length of the sensor was about 1.5 mm and the area of the diaphragm was 1 mm x 1 mm. The phase shift of the interferometric sensor was proportional to the applied pressure. The relationship between the applied pressure and the phase change was nonlinear.

A fringe pattern correlator (FPC) for three-dimensional (3D) object recognition is developed using a spatial frequency multiplex color grating (SFMCG) to avoid phase ambiguity problem. The SFMCG consists of multiple color gratings with different carrier frequency. When the SFMCG is projected onto a 3D object, a color deformed grating pattern modulated by 3D shapes is obtained. Using color decomposition techniques, multiple monochromatic deformed grating patterns can be extracted from the color deformed grating pattern. Because the FPC in different sensitivity is easily executed using these monochromatic deformed grating patterns, exact 3D object recognition can be performed.

Intensity correlations of speckle patterns formed by multiple scattered light from a powder bed are investigated experimentally. Decorrelation of the speckle patterns is measured by changing the angle and the area of laser beam illumination. The proportional relationship between the transport mean free path and the average particle diameter is obtained when the powder samples of the same type are used in the angular correlation measurements. It is also found that the particle size affects the speckle decorrelation due to the translation of the illuminating area on the powder surface. This result exhibits a contrast to a single scattering diffuse object for which the degree of speckle correlation is independent of the characteristics of the diffuser.

We have constructed a simple small-sized lock-in light detection system using a gated Si avalanche photodiode (APD). The gate mode operation of the APD was achieved by a transistor-transistor-logic (TTL) signal superimposed on a direct current (dc) bias not exceeding the breakdown voltage of the APD. The attainable gain was thirty times larger than that obtained by the normal dc-biased APD. The APD is operated at a frequency of 2f (equals 20 kHz) and its output signal is fed into a compact laboratory-made lock-in amplifier that works in synchrony with the gated APD at a frequency f (equals 10 kHz). The system is useful for detecting a weak signal light superimposed on a large background.

We report experimental results in which Mie particles were optically propelled in an evanescent field generated in a multimode channeled waveguide. Polystyrene latex spheres 4 micrometers in diameter were trapped laterally in the high intensity region of an evanescent field and were driven along the waveguide channel in an evanescent field of either fundamental or higher guided modes. In addition, when the multiple guided modes are excited simultaneously, the distribution of the meandering light's intensity is generated in the waveguide due to the coupling of the modes. The small particles are laterally trapped even in this meandering beat pattern and driven in a meandering fashion along the waveguide channels.

We present a novel interferometer fiber optic sensor (IFOS) system for DC signal measurement based on the PGC (phase generated carrier) demodulation scheme. In addition to the principle of the demodulation, the compensation techniques for improving the measurement precision constrained by the laser nonlinearity in frequency modulation (FM) operation and the experimental results are described. And now, we've made a prototype water level sensor and been trying the field tests, so we show the first results compared with those of the float-typed reference sensor.

Modulated principles of various intensity-based sensors and their industrial applications are presented in this paper. We also presented a novel fiber optic sensor with a special construction like a spoke and the sensor was composed of a single mode emitting fiber as well as eight multimode receiving fibers. This special construction can compensate the light fluctuation and reflectivity variation of the measured surface. What's more, with the novel arrangement of the receiving fibers, it can also improve the slope impact in case of the sensor is used to measure the value of spatial height of a surface. Thus, it can be used to measure a complex surface contour with a fairly good resolution and sensitivity. The preliminary experiments were made to verify the practicability and reliability. The estimated local and vertical resolutions can reach 8 micrometers and 0.1 micrometers , respectively. This sensor system was applied to measure a MJ thread and small shoulder height. The conclusion is made that the developed sensor is suitable for complex surface shape measurement with higher speed, higher accuracy, and can be very good used in industrial application.

We propose a phase-modulation fluorometer that is applicable to a very weak fluorescence intensity level. In order to counter the single-photon event situation, we have introduced a combination of a time-to-amplitude converter (TAC) and a pulse height analyzer (PHA) to the phase- modulation fluorometer, the combination of which is usually used in the single-photon correlation method to measure fluorescence decay waveforms by pulsed excitation. In the proposed fluorometer, a sinusoidal response waveform that is shifted in phase over the reference one is obtained statistically as a histogram in the PHA memory and then the fluorescence lifetime can be calculated by the same procedure as the conventional analog phase-modulation method. The excitation light source used was a current- modulated ultraviolet light-emitting diode (UV LED), whose center wavelength was 370 nm and its spectral bandwidth was 10 nm. Fluorescence lifetimes of 17.6 ns and 5.7 ns obtained for 10 ppb quinine sulfate in 0.1 N H₂SO₄ and for 10 ppb rhodamine 6G in ethanol, respectively, agreed well with those reported in the literature.

In this study, we synthesize a new iridium complex by introducing sterically bulky spacers into the framework of fac tris(2-phenylpyridine) iridium [Ir(ppy)₃]. The main purpose is to reduce concentration quenching in Ir(ppy)₃. The new complex exhibits a high (0.71) photoluminescence (PL) quantum yield in solution. The devices fabricated with the new Ir complex as an emitting dopant confirm that concentration quenching is almost negligible even at relatively high doping concentrations. For example, at a current density of 100 mA/cm², the current efficiency for the devices with 7 and 26 wt% dopants are 8.9 and 10.2 cd/A respectively. These characteristics can be explained by a better energy transfer between the host and dopants upon introducing the sterically hindered spacers into the phosphorescent dyes.

In this study, we examine the switching time of photonic memory devices, which we calculate for several switching schemes. Using the numerical results, we find that the switching scheme in which the switching is mediated by applying a small dc field to the device is the fastest one.

A shape-free coupling hole type laser is proposed to extract and transmit various output patterns by using the coupling hole mirror having an arbitrarily shaped hole. This configuration is demonstrated by combining a slow axial flow CO₂ laser with two types of coupling mirrors having two holes or a ring-shaped hole. Two different coupling hole mirrors are fabricated by evaporating gold film on the ZnSe substrate onto which the masks for the coupling hole are attached. The lasing output is successfully obtained along with the pattern transmission characteristics.

Wavelength division multiplexing (WDM) systems can offer large capacity of the optical fiber communication. However, it requires the wavelength selective add-drop filters. A novel tunable wavelength filter, consisting of fiber grating and movable diaphragm, is proposed and fabricated by using a surface micro-machining technology. By moving the diaphragm at near the side polished fiber, the effective refractive index of the fiber core is controlled. This modulation of effective refractive index of the fiber core enables to control the wavelength of the fiber Bragg grating.

We analyze the polarization state in the enhanced backscattering of light under the double-scattering approximation. The asymptotic expansion of the enhanced backscattering of light is derived for simplicity. The spatial polarization anisotropy of the enhanced backscattering are numerically demonstrated. It is shown theoretically that the decreasing behavior of intensity distribution depends on the fractal dimension of aggregated particles.

Mordant Pure Yellow azodye in a matrix of gelatin is proposed as a media for stable polarization recording. Relatively high values of birefringence are measured (over (Delta) nequals0.02). Polarization diffraction gratings are recorded with two circularly polarized waves and diffraction efficiency of 67% is achieved at 633 nm. Protected from the humidity, the recording is stable. Long term radiation by 633 nm probe beam is harmless as well. Unusual behavior is observed when acting on the recorded grating alternatively with one of the recording beams. The left circularly polarized beam erases the grating sharply, while the right circularly polarized beam, before erasure, first increases the diffraction efficiency.

This paper reviews the recent progress of application of interactions between optical near-fields and nanoscale materials. Photochemical vapor deposition of nanometeric Zn and Al are realized by using a UV optical near-field. Deposition of nanoscale ZnO is also shown. Utilizing the very advanced potential of this technology, the concept of nano-photonic IC is proposed. The optical switching operation of a single InGaAs quantum dot is shown to be able to be used for nano-photonic devices. Nano-photonic switching operation utilizing optical near-field interaction is also proposed and related spectroscopy of CuCl quantum dots are demonstrated. High-density storage and read-out by optical near-field is also demonstrated. Atom manipulation by the optical near-field is reviewed briefly.

Photonic crystal fiber (PCF) is a single-material all-silica structure. Initially proposed by the author in 1991, the first working example was reported at the Optical Fiber Communications Conference in 1996. In place of the conventional core and cladding, an array of microscopic air holes runs along the entire length of the fiber. Depending on the design, light can be trapped by two distinct mechanisms: a modified form of total internal reflection (at a filled-in hole) or by a photonic bandgap (e.g., at an enlarged hole). These unconventional fibers have led to a series of breakthroughs that is radically enhancing the performance of optical fibers. The disruptive implications of the new technology are just beginning to be worked out.