The standard expression for the excited state acceptor concentration in codoped solid-state materials is modified to include the possibility of non-radiative acceptor de-excitation. The chromium and thulium time-dependent emission in yttrium aluminum garnet (YAG) is then studied; evidence is given for the identification of the tendency for localized correlated chromium-thulium pairs in the crystalline material.

We have used a copper vapor laser amplifier of 80 mm tube diameter to amplify a 10 watt laser beam to a 100 watt level. The output beam was found to be elliptically polarized, and the eccentricity and the direction varied over the beam cross-section. Assuming that the polarization changed due to the temperature gradient in the laser amplifier windows, we have compared spatially resolved calculations to spatially averaged measurements. Our calculations show that the described behavior stems from the high tube temperature of the copper vapor laser which may exceed 1600 degree(s)C. As a result, the windows were heated by IR radiation, causing a cylindrically symmetric temperature distribution. The temperature gradient causes a mechanical stress, and a circularly symmetric birefringence. Acting on the vertical polarization, this birefringence leads to the spatially dependent depolarization. We have analyzed the average polarization and studied two ways to increase it. The vertical to horizontal ratio was about 4:1 for 12 mm windows, 9:1 for 6 mm windows and 19:1 for 6 mm shaded windows. The experimental results were in good agreement with the calculations.

The angular field of view (FOV) of a Brillouin amplifier is shown to be dependent upon the spectral bandwidth of the interacting beams. Theory and experiment reveal that for single longitudinal mode pulses of 8.5 nsec duration interacting in CS₂ the FOV is equal to +/- 18 degree(s) in a counterpropagating geometry. Proper design of the amplifier is required however, in order to take advantage of the full FOV afforded by the Brillouin interaction.

Shot-to-shot stability of organic liquid based phase conjugate mirrors was studied experimentally and theoretically in order to define stable operating regimes when incorporated into pulsed laser systems. Reflectivity over five orders of magnitude was measured and the standard deviations were analyzed. A general dependence between standard deviation and reflectivity was found to occur. Good stability (+/- 2%) was achieved at reflectivities of 80% when the input laser energy was 5 to 10 times greater than threshold.

We examine how two nonlinear optical signals generated by a multimode laser will interfere. This interference is shown to be analogous to linear interference with partially coherent light. Consequently, we demonstrate an interferometric method for determining the temporal and spatial coherence of a laser, which features no moving parts and does not require precise ultrashort mechanical translations.

An azo dye, methyl red (MR), was introduced into glass films and bulks and into polymer films. The glasses were either pure silicate or composed of a silicate network with the addition of long chain organic molecules. Some glasses were composites of silicate and methyl methacrylate (MMA) or poly(vinyl acetate) (PVAc). The polymer films, which consisted of PVAc or poly(vinyl alcohol) (PVA), were deposited on glass plates. The induced transparency of the samples was measured by a pump and probe method, using the 488 nm line of an argon- ion laser for both the pump and probe beams. The nonlinear effect was observed with the neutral and basic forms of MR (orange and yellow, respectively). The magnitude of the effect decreased with increasing density of the host as follows: polymer matrices, composite glass, sol-gel glass. These results, as well as measurements of the excited state spectra, are consistent with the hypothesis that the observed nonlinearities are the result of a trans-cis isomerization of MR, for optical excitation in the milliwatt range.

Introducing an intracavity polarizer into a Fabry-Perot, birefringent, Nd-doped fiber laser, produces a fundamental change in the laser spectrum. The change is a consequence of the wavelength dependent loss which is inflicted by the polarizer. In two set-ups described, tuning and a comb-like spectrum are easily produced.

Fiber-optic ring structures with multiple recirculations are reviewed and their applications for the accurate measurement of a variety of physical measurants are analyzed. The methods are based on the fact that minute changes in the round trip time around the loop, are amplified after many recirculations, thereby making them measurable quantities. Some new possibilities of measurements are proposed. Analog self-oscillations and optical pulse multiple propagation are considered. Influences of length of fiber, parameters of optical radiation and pulse form on characteristics of such devices are observed.

In acousto-optics there exists a trade off between the maximum modulation frequency and the maximum incident beam power that can be modulated. A projected increase in power- bandwidth product will lead to a significant increase in transmission distance for long distance atmospheric optical communications. This paper describes our investigation of certain anomalies of the acousto-optic interaction in the region of theoretical upper limit of modulation frequency and of the beam power that can be modulated. The current investigation has shown that under certain conditions the efficiency of AOM performance and its bandwidth could be considerably increased. We further investigated unique properties of multi-order Bragg diffraction structure which can be observed at high modulation frequencies. This paper discusses work in progress which could lead to the development of acousto-optic modulators capable of modulating up to one half watt of optical power at frequencies of up to 100 MHz.

The present review describes all-optical devices based on appropriate organic materials that will operate on the intensity induced changes in the complex index of refraction, i.e., the absorptive and dispersive properties of the medium due to intensity induced population changes. Theory predicts that optical bistability can be observed in such materials, as well as realizing molecular SLMs. A kinetic analysis of a general multilevel nonlinear organic absorber is performed. The analysis is used to derive an expression for the complex nonlinear- molecular index of refraction. The properties of a molecular SLM based on this absorber are discussed as well as a similar device based on a photochromic material. In addition, the transient behavior of a triplet SLM at short time excitation is examined. Optical bistability based on the same nonlinear optical properties is also studied. The calculations are supported by a series of experiments in which novel materials based on intense triplet-triplet absorption are measured. These materials serve as the nonlinear media for prototype molecular SLMs, transient wave-guide switching and optical bistable elements.

Measurement of the time-response of the excited-state concentration of manganese has confirmed our previous hypothesis of fast energy transfer between manganese and neodymium in fluoride glasses.

The rare earth ion doped yttrium aluminum garnet crystals or YAG are widely used as lasing materials and for other quantum electronic device applications. Robbins et al. and Gibbons et al. showed that at least one type of defect is responsible for the wide 300 nm luminescence band observed in photoluminescence and cathodoluminescence. These defects, which are inherent to pure YAG, influence the excitation energy transfer to the rare earth ions, the luminescence kinetics, etc. This ensures the importance of detailed information about the structure of these defects. To explain the temperature dependence of the luminescence kinetics and the stationary luminescence spectra, Robbins et al. proposed the existence of at least three types of the centers. They explained the temperature dependence of the luminescence decay times to be a result of the consequent ionization of these centers. The aim of the present work is to prove that the experimental results of Robbins et al. can be explained in the framework of the model incorporating centers of one type only. These are electrons bound by the oxygen vacancy.

The success in lasing of Cr⁴⁺:forsterite in the near IR had motivated a search for new crystalline hosts for Cr⁴⁺. Silicates and garnets containing distorted tetrahedral crystalline sites are suitable for accommodating tetravalent chromium ions. In the present paper we compare the structural and spectral characteristics of Cr⁴⁺ doped YAG, Mg₂SiO₄, Ca₂Ga₂SiO₇, Ca₂Al₂SiO₇ and Y₂SiO₃ crystals, as well as their growth conditions. The applications of these materials as tunable solid state lasers and passive Q-switches for pulsed Nd lasers are discussed.

Real-time recording of mid-infrared laser radiation in photochromic spiropyran-MMA copolymer materials is investigated. The laser radiation, derived from a CO₂ laser, bleached pre-colored merocyanine, thereby converting it back to spiropyran. The exposure sensitivity at 50 percent of the initial merocyanine optical density was about 0.1 J/mm² at 10.6 micrometers laser wavelength and 0.2 J/mm² at 10.5 micrometers . The difference of sensitivity at the two laser wavelengths points to differences in thermal energy dissipation mechanisms. The characteristics and examples of imagery, recorded in these photochromics, are presented. A resolution equal or better than 40 lines/mm was achieved.

A necessary part of digital image processing is segmentation of the images into a set of objects which exist on some background. We are interested in a class of objects whose distinguishing characteristic is their color. Such objects occur in many applications, such as microscopy, printing, production line monitoring, etc. In this work, a general method of rapid color-based segmentation is presented. The only hardware requirement is that look up tables (LUT) be available. Most image processing hardware contains either LUTs or processors capable of rapidly performing table lookup. The method presented allows simultaneous application of constraints on both hue and saturation. In addition, it allows for use of different color transformations. As such, it constitutes a general approach to analysis of images consisting of three spectral components. Because of the speed of LUT operations, this approach is suitable for many applications which are time sensitive. The major drawback of using LUTs is that the gray level resolution per color is limited by the size of the LUT. This method was implemented on a Matrox MVP-AT image processor, which is capable of processing 12 bit images (4 bits/color). In many cases, this resolution is adequate, as can be seen from examples which are presented.

Optical processors for neural networks are primarily fast matrix-vector multiplication machines that can potentially compete with serial computers owing to their parallelism and their ability to facilitate densely connected networks. However, in most proposed systems the multiplication supports only two quadrants and is thus unable to provide bipolar neuron outputs for increasing network capabilities and learning rate. We propose and demonstrate an opto-electronic four quadrant matrix-vector multiplier that can be used for feedforward neural networks recall and learning. Experimental results obtained with common commercial components demonstrate a novel, useful, and reliable approach for four quadrant matrix-vector multiplication in general and for feedforward neural network training and recall in particular.

Optical pattern recognition techniques based on the optical joint transform correlator (JTC) scheme are attractive due to their simplicity. Recent improvements in spatial light modulators (SLM) increased the popularity of the JTC, providing means for real time operation. Using a binary SLM for the display of the Fourier spectrum, first requires binarization of the joint power spectrum distribution. Although hard-clipping is the simplest and most common binarization method used, we suggest to apply error-diffusion as an improved binarization technique. The performance of a binary JTC, whose input image is considered to contain additive zero-mean white Gaussian noise, is investigated. Various ways for nonlinearly modifying the joint power spectrum prior to the binarization step, which is based on either error-diffusion or hard-clipping techniques, are discussed. These nonlinear modifications aim at increasing the contrast of the interference fringes at the joint power spectrum plane, leading to better definition of the correlation signal. Mathematical analysis, computer simulations and experimental results are presented.

Utilization of 8 - 10 micrometers spectral band symmetrical, and 3 - 5 micrometers band asymmetrical GaAs/GaAlAs multiple quantum well (MQW) structure for a multiple color detector is discussed. A theoretical comparison between the predicted performance of a GaAs-MQW based focal plane array (FPA) operating in the 8 - 10 micrometers band, and state of the art narrow band gap (MCT, InSb) operating in the 3.2 - 4.2 micrometers band is given. We show that because operating in the 8 - 10 micrometers band even with 0.2 quantum efficiency the noise equivalent delta temperature is better than the theoretical limit at 3.2 - 4.2 micrometers IR FPA.

Free-space optical interconnects are exploited to solve general purpose computing tasks which remap structured sets of information. These tasks -- viz. load balance, monitoring, fault tolerance, shadowing -- can all be based upon elementary message patching operations. It is shown that usual assumptions in optical computing -- the redundancy of numbers, as in dual rail representation -- suffice to perform recoding, thus patching, in elegant ways. Smart recoding schemes, may be even less redundant than dual-rail. For monitoring of large-scale computer systems, small numbers of smallitors are added/removed as needed in between processor clusters. Smallitors Snatch-&-Patch messages, by intercepting and partially deflecting optical information. Smallitors are small in size and in complexity. Once one is given enough bandwidth, the next critical limiting resource is latency. This is a prime reason behind the on-the-fly patching approach in free-space optics. Smallitors strive to minimize latency, by turning on additional bits in parallel, thereby recoding the transmitted ones. Recoding schemes and their optical implementation, are discussed within concrete computing tasks. Observations from actual prototypes are also considered.

The infrared optical constants (index of refraction and extinction coefficient) and reflectance of bulk-doped n-silicon are calculated for electron concentrations up to 10²¹ cm^-3. These calculations are based on generalized Drude-Lorentz form of dynamic dielectric function and current relaxation approach. A nonmonotonic behavior of IR absorption versus electron concentration is found. A connection between the theoretical results and available experimental data is discussed.

A method for designing a large scale holographic interconnects system is presented. The building-block of the interconnects system is composed of two identical holographic optical elements (HOEs), which are recorded on the same plate. To achieve both high diffraction efficiencies and diffraction limited performances, the holographic elements are recorded with predistorted wavefronts which are taken recursively from interim holograms. To provide optical interconnections for a large number of source-detector pairs on the same board, a method for recording simultaneously a large number of building blocks on the same recording plate, is presented. With this method, the HOEs are recorded by reconstructing simultaneously the `parents' holograms, which are pre-prepared on an intermediate plate, and using the output beams to record the final elements. A special recording geometry is suggested in order to prevent cross-talk between the various HOEs, and to assure high diffraction efficiencies and low aberrations for all the interconnects.

A method for designing and recording a holographic achromat, composed of two holographic optical elements (HOEs), is presented. The method is demonstrated with a doublet recorded at 488 nm for application at a central frequency of 820 nm. A near-diffraction-limited focus and high diffraction efficiency are achieved over a comparatively wide spectral range.

A method for designing and recording Fourier transform holographic lenses, in the presence of a recording-readout wavelength shift, using a substrate-mode holographic doublet, is presented. The system is composed of two holographic optical elements (HOEs) which were recorded on the same plate. The first one couples the various spatial frequencies of the input into plane waves which are trapped inside the plate by total internal reflection. The second HOE focuses the collimated waves into the Fourier plane. Since the chromatic dispersion of the first hologram can be corrected by the dispersion of the second hologram, this system is much less sensitive to source wavelength shifts. The method is illustrated with a compact system, recorded at 458 nm and reconstructed at 633 nm. Near diffraction limited performance and a comparatively low chromatic sensitivity over a wide field of view has been obtained.

The process, chemistry, and characterization of the silylation and dry-development of acid catalyzed resist is described. The resist is sensitive to deep-UV, x ray, and e-beam exposure and its sensitivity can be tailored by the relative concentration of its components. The resist is positive or negative for dry or wet development, respectively. Two silylation agents were studied: Hexamethyldisilazane (HMDS) and N,N-Dimethylaminotrimethylsilane (DMATMS). The silylation was characterized by Fourier-transform-infrared (FTIR) transmission spectroscopy and Rutherford-backscattering spectrometry (RBS). FTIR revealed the total number of OH and SiO bonds, while RBS revealed the composition profile in various regions of the resist. The silylation by HMDS was not well controlled and was characterized by a large incubation period followed by fast penetration. The DMATMS silylation process, however, was well controlled and reproducible. The penetration of the silicon atoms monotonically increased with time until it reached saturation. Films patterned by deep-UV (254 nm) exposure were silylated with DMATMS and were etched by an oxygen plasma in a magnetron ion etcher (MIE). The etch rate of the oxygen plasma was characterized for the unexposed, silylated regions, as well as for the exposed, unsilylated regions. The optimized dry-development process is described and SEM cross sections of lines as narrow as 0.4 micrometers wide are presented.

It is shown that the photosensitivity of photoresists based on chalcogenide glasses can be increased drastically (1000 times and more) using excitation by pulsed radiation of excimer laser. A model is developed that explains the increase in sensitivity. The main advantages of chalcogenide photoresists are discussed and conclusions are drawn on the prospects of these resists for submicron photolithography.

Microlenses can be made by refractive and diffractive optics. A tailored distribution of light creates, in exposed photoresist, a three dimensional pattern, which is then reproduced by ion beam etching in the substrate, resulting in the desired microlens. The first technique uses a Fraunhofer diffraction pattern of a hole in the focal plane of a lens. The second technique uses diffractive optics, i.e. a Dammann grating, to generate a uniform array of equally spaced beams. The theoretical background of a Dammann grating and the experimental results are presented.

This paper presents our experiments towards improved CD control over 4000A' poly steps using a single layer resist. The techniques used for reduction of CD variation were a special develop process to enhance surface inhibition effect, the use of dye additive and increase of resist thickness. As resist thickness varies over the poly steps it goes through various minima and maxima of the swing curve. This phenomenon causes the line width to vary and forms a challenge to modern lithography as shrinking design rules are more and more demanding, and CD variation due to topography can cause the device to fail. We have looked at the effect of dye additive, a special develop process and choice of thickness on CD control, focus and exposure latitude. The recommended process is chosen based on those parameters and presents the best achievable results with single layer resist. The geometries we investigated were 0.5 and 0.6 Micron showing that an acceptable process window for those geometries is achievable under a production environment.

Low-melting glass ceramics were developed to form coatings that protect circuits on alumina substrates from corrosion. The influence of (beta) -eucryptite and nitrides on its thermal expansion and crystallization were studied. The coatings, formed from powdered glass at firing temperatures from 430 degree(s) to 480 degree(s)C, have thermal expansion coefficient in the range (95 -85) X 10^-7 degree(s)C. High resistance to thermal shock of coatings is due to the presence of crystal phases: 2PbO.ZnO.B₂O₃ and (beta) - eucryptite. At the surface of the coatings can be seen `islands' of nitrides hydrophobic thin film.

Various oxide films were prepared by oxygen ion-assisted deposition. The ion source (Mark II Gridless Ion source, manufactured by Commonwealth Scientific Corp.) uses the End-Hall configuration and generates high-current, low-energy beams of ions. Films of TiO₂, SiO₂, Al₂O₃, Y₂O₃ were deposited on substrates in temperatures ranging from ambient to 200 degree(s)C. The films had a high index of refraction, were hard and adhered strongly to the substrates, as compared to conventionally deposited oxide films. Multilayers of TiO₂/SiO₂ were prepared giving hard and environmentally stable coatings.

Laser technology enables a specimen surface to be melted and alloyed without the substrate itself being heated, whereby a surface with special attributes is obtained while the properties of the substrate are unchanged. The surface of Armco iron, AISI 1045, and AISI 1095 steels were laser alloyed with TiC powder, using a CO₂ laser of 2.5 kW maximum power. Optimal laser and powder feed parameters were established. Particles of TiC were injected into the molten surface layer, forming a composite material, steel + TiC. The microstructures were investigated metallographically. Some of the particles had partially melted during their passage through the laser beam and had re-solidified, forming small and fine dendrites. Surface hardness increased, mainly due to the presence of these undissolved TiC particles. A new mathematical model describing the alloying process, based on the equation of heat conductance, to the alloying process is presented.

Surface treatment by lasers has not become established in industry. In part, this is due to conservative attitudes of users, an unwillingness to adopt new techniques as well as for same applications technical reservations as the side effects of laser treatments are insufficiently understood or documented. There are, nevertheless, a steadily increasing number of applications of lasers in surface engineering. In this paper the possibilities of surface treatment are reviewed and some examples of industrial applications given. Three types of laser are available: CO₂, Nd:YAG, and Excimer laser. In this paper we restrict the discussion to CO₂ lasers.

The experimental processing of rocks shows the possibility and advantage of laser cutting especially for complicated shapes in plates to 25 - 30 mm thick. High productivity and good quality of cut surface make this technology competitive with traditional mechanical methods. Engraving with laser radiation is rapid and allows formation of clear images and pictures on rock surfaces. It enables the formation of decorative patterns of varying depth for volume images. Experimental results encourage the establishment of an industrial laser center for rock surface processing. The new generation of medium and high power rf excited diffusive cooled lasers are particularly suitable for this purpose.

The UCL-700 (ultra compact laser) is capable of delivering up to 800 watts of cw 10.6 micrometers radiation, suitable for industrial applications such as cutting, drilling, welding and heat treatments. The laser cavity is 50 cm long by a 6 cm diameter and the complete laser head weighs less than 30 Kg. The laser's structure and operating principles are presented and some performance results are shown. Power upscaling developments together with known experimental data show that with a few modifications power extraction from the cavity can be more than doubled.

A novel industrial CO₂ laser is presented, based on a proprietary combination of rf excitation, conductive cooling and a specially fitted resonator, conforming with size and shape of the discharge. This design results in the most compact laser-head of the kilowatt-class that is available on the market. The current model, ICCL 1000, generates about 1200 watts, in a high quality beam suitable for metal-cutting applications.

A possible scheme for performing vibrational phase and amplitude mapping using pulsed interferometry is presented. Both the case of electronic speckle pattern interferometry (ESPI) and of conventional holographic recording (HI) are treated. The proposed methods utilize the possibility of performing optical phase shifting, and the number of required interferograms are kept at a minimum.

We describe a novel acousto-optical method for measuring the size of bubbles in an ambient fluid. The method employs optical means to determine the acoustic resonant frequency of the bubbles, and hence infer their sizes. This method obviates the need for strict optical calibration, which characterizes presently available methods for bubble-sizing. It is simple and inexpensive, produces accurate results, and may be used for determining the sizes of moving or stationary bubbles.

A high irradiance short pulsed Nd:glass operated in TEM₀₀ mode was used to generate shock waves in different materials to study their behavior at dynamic stress condition. Dynamic fracture at hypervelocity impact regime was observed as a result of reflected shock waves as tensile waves from the back surface of the samples. Damage development from incipient spallation to complete sample perforation were obtained for planar and hemispherical shock waves. Maximum elongation at fracture at ultra high strain rate was measured for several metals. Shock wave attenuation and dynamic strength were evaluated for metals and composites. A linear dependence was obtained for the pressure decay as a function of target thickness for planar shock wave. The experimental results of threshold for spall and spall width at this energy were compared with numerical simulations. The laser pulses were also used to generate hemispherical shock waves in targets (focal spot smaller than target thickness). A linear experimental relationship was obtained between laser energy for threshold spall conditions and the cubic target thickness. This relation is equivalent with the propagation of a strong point explosion where the internal energy per unit volume of the shocked materials is constant. The shock wave was modeled by an expanding pressure front, which creates micro-damage in the laser impacted layer and extrudes a bulge at the far surface. The calculated bulge size compares well with that observed by us for metal-adhesive-metal sandwiches. The micro-defects joining into macro-damage or fracture can be described by percolation theory.

We present a new type of intensity-modulated sensor based on a coated lightguide. Using a physical model of the coated lightguide the output light intensity was computed as a function of the reflection and transmission complex coefficients at the substrate-film and film-ambient interface. Based on these theoretical results an experimental setup for measuring various parameters of a liquid was constructed. The results demonstrate the dependence of the output signals on the characteristics of the substrate-film-ambient system. In particular the output signal increases for some incidence angles as the refractive index of the ambient medium increases.

The micro-optic Fabry-Perot interferometer as a spectral transducer for fiber optic sensors is described. Signal processing includes the simultaneous detection of several resonances of the FPI response function in the spectral domain and the recovery of interference order for the exploited resonance. The application of this approach in displacement pressure and temperature sensors is demonstrated. The absolute accuracy of displacement sensing less than 1 nm was obtained. The dynamic range of the devices based on the proposed principles can be as large as 50 dB.

Infrared (IR) fiber optic radiometry of thermal surfaces offers several advantages over refractive optics radiometry. It does not need a direct line of sight to the measured thermal surface and combines high capability of monitoring small areas with high efficiency. These advantages of IR fibers are important in the control of nonuniform temperature and emissivity distributions, in which the parameters of closely situated points differ considerably and a high spatial resolution is necessary. The theoretical and experimental aspects of such radiometry are discussed in this report. Theoretical and experimental radiometric output functions of the sensor during scanning of an area with a nonuniform temperature and emissivity distributions were obtained and their dependence on the spacial location of the fiber and type of distribution were analyzed. The results suggest that IR fiberoptic radiometry will be useful in industrial, medical and domestic applications.

A method for establishing a cost-effective computerized radiometer/photometer was developed. The system utilizes standard equipment. Luminances of small areas as well as large areas can be conveniently measured. The radiophotometer is especially suitable for automatic monitoring of luminances of light sources with fixed spectrum.

The linear birefringence exhibited by the wound fiber in a Faraday rotation current sensor is shown to be responsible for a significant dependence of the output signal on the location of the conductor within the fiber loop, and for non-zero outputs for conductors outside the loop. Numerical calculations show a signal variation of up to approximately equals 10% as the conductor is moved around the circumference of the loop.

A Lyot depolarizer is used in a bit-rate-limiter of the Mach-Zehnder type in order to reduce the phase induced intensity noise, which otherwise, sets a floor on the bit error ratio. Results show an improvement of 3 dB, at the expense of longer arms and a more complicated design.

A red perylene derivative was impregnated into a composite silica-gel glass, and characterized as a dye laser material. The absorption spectrum in the range 480 - 600 nm belongs to the S₀ - S₁ electronic transition, with a structure reflecting the perylene skeletal vibrations, of typical energy 1100 - 1200 cm^-1. An additional peak between 400 and 460 nm belongs to the S₀ - S₂ transition. The fluorescence exhibits a mirror image relative to the S₀ - S₁ absorption, with a Stokes shift of about 40 nm for the 0 - 0 transition. Laser tunability was obtained in the range 605 - 630 nm using a frequency-doubled Nd:YAG laser for pumping ((lambda) equals 532 nm). This wavelength range is important for medical applications, such as photodynamic therapy of some cancer tumors. Maximum laser efficiency of approximately 2.5% was obtained at 617 nm. Maximum output was approximately 0.36 mJ/pulse at a repetition rate of 10 Hz. Minimum laser threshold obtained was 0.45 mJ/pulse. The medium losses are attributed to an excited-state singlet-singlet absorption, with an upper limit cross-section of approximately 2.5 X 10^-16 cm². The laser output was stable over more than approximately 500,000 pulses, under excitation with the green line of a copper vapor laser (510 nm), of energy density approximately 40 mJ/cm² per pulse. Good prospects exist for a considerable enhancement in laser output efficiency.

The architecture of trabecular tissue in the femoral neck plays an essential role in determining its resistance to mechanical loads. In the present study, we suggest a quantitative technique for analyzing the pattern of bone trabeculae on a conventional radiograph of the femoral neck. The method is based on optical image processing of the radiograph in order to obtain the two- dimensional power spectrum of the trabecular distribution. A one-dimensional analytic model has been developed to describe the light distribution transmitted through a region with a trabecular pattern on the radiograph. This model is able to simulate the changes which appear in the transmittance curve during the process of trabecular resorption. The resulting changes in the power spectrum of the trabecular distribution have been calculated in order to determine accurately the spectral shift which characterizes the change in the trabecular pattern. The light intensity in the Fourier plane of the optical system was analyzed to obtain experimentally the power spectrum of the trabecular pattern. The power spectrums resulting from the model were similar to those obtained by the optical Fourier Transform of the radiographs. The two dimensional power spectrum in the optical Fourier plane was analyzed in different directions. We found that different frequency range contributes to the spectrum in each direction. These results imply that optical Fourier analysis of the trabecular pattern on a conventional bone radiograph is a potential tool to characterize the structural changes occurring in the osteoporotic process.

A photoplethysmography (PPG) device, which filters the dc signal without distorting the pulse shape, was developed. Measurements were performed on the finger, for hand at heart level, below and above it. The PPG signal was highest above heart level, and lowest below heart level. It seems that the compliance and the resistance of the blood vessels influence the PPG curve.

Measurement of uncovered skin surface temperature by measuring the infrared radiation emitted from the skin does not provide useful information about the blood temperature and blood flow. The information obtained from the same measurement for thermally insulated skin is more significant. The skin is insulated by a special device, which permits partial transmission of the infrared radiation through it. Preliminary results show that skin blood flow and under-skin temperature can be assessed from measurements of radiation transmitted through the thermal insulation which was applied to the skin.

Since the advent of soft contact lenses, no solution had been found for accurately and easily testing these lenses. The same systems that had been used for testing dry lenses were applied. This resulted in difficult training of each operator in properly drying the lens, and then quickly testing it before it dried too much causing large power changes. Lenses were not tested in solution because the decreased accuracy caused by the refractive index of the solution was much lower than what was allowable. With the moire deflectometer, a new method has been developed for testing soft lenses in their saline solution, with a much higher accuracy than what is required by the market. In addition, the moire deflectometer allows the quantitative testing of lens quality, and a straight forward method for testing toric lenses. Multi focal lenses can also be analyzed and tested.

Laser microscopic videofluorimetric device has been constructed. Specifically induced spectral characteristics of malignant and healthy tissues fluorescence in the region of 280 - 770 nm have been developed. New experimental results of malignancies identification and their diagnosis have been obtained.

The value of the refractive index of a thin film material in a multilayer coating is dependent both on its ordinate number in the stack and on its neighboring materials. Incorporation of such empirical data in the simulation of optical coatings narrows the gap between designed and actual coatings' performance. It makes feasible some designs which were not practical before.

A new effect concerning the interaction of electromagnetic waves with surfaces is represented. It was observed that when organic molecules, like naphthalene and aniline, were absorbed on a metal surface, enhanced photoemission signals were detected. The signal as a function of the wavelength of the illuminated light reflected the absorption spectrum of the absorbent. This effect was called the surface-enhanced photoionization.