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We have developed a new Acousto-Optic Tunable Filter (AOTF) for implementation as a spectrally selective element for hyperspectral imaging applications in the NIR (.8 - 1.7 micron) and MWIR (2.5 - 4.5 micron) ranges of the optical spectrum. The new AOTF has high spectral resolution (about 3/cm) and requires relatively low RF drive power. It has a broad acceptance angle and increased diffraction efficiency for enhanced optical throughput. In combination with a 2-D IR focal plane array the new AOTF allows for real time hyperspectral imaging of both self-emitting sources, such as astronomical objects or rocket exhaust plumes, and externally illuminated absorbing/reflecting specimens., See Also ADM201041. IRIS Proceedings (1998) on CD-ROM. Prepared in cooperation with Air Force Research Lab. Hanscom, AFB, MA.

This work was aimed at optimization of the photorefractivity in the II-VI semiconductors CdTe, ZnTe and Cd(x-1)Zn(x)Te for real-time optical signal processing applications at near infrared wavelengths. During this work, several crystals of ZnTe, CdTe and Cd(x-1)Zn(x)Te were grown. Crystal growth of ZnTe and CdTe was carried out using low supersaturation nucleation and "contactless" growth by Vertical Physical Vapor Transport (PVT) in closed ampoules and the CdTe and Cd(x-1)Zn(x)Te crystals were grown using the vertical Bridgman technique. The quality of the crystals grown during this work was evaluated based on optical, electrical and structural characterization. Infrared microscopy was used to examine the internal crystalline structure of the samples. Most of the crystals grown during this work exhibited photorefractivity and photoconductivity. The resistivity of the vanadium doped crystals under dark conditions was found to be between 10 (exp 8) to (exp 10) ohms cm. The resistivity decreased significantly in the presence of illumination indicating that the crystals were highly photoconductive. The photorefractive properties of the crystals grown during this project were characterized by two beam coupling. All of the measurements revealed a strong photorefractive nonlinear effect.

During this project, we have developed and produced application quality photorefractive Cd(1-x)Mn(x)Te:V crystals with compositions x= 0.15, 0.45, and 0.60. These crystals are useful for applications in the wavelength range of 0.7 to 1.3mm. These crystals were obtained through the following material processing steps: (1) extensive purification of the starting elements (cadmium, manganese and tellurium) and purification if the compound (Cd(1-x)Mn(x)Te); (2) crystal growth from the melt under controlled conditions of heat and mass transfers; and (3) in situ annealing of the crystals after growth. The optimal temperature profile required to produce a favorable growth interface and minimal stress for crystals grown by the Bridgman- Stockbarger method was determined. From computational models, the temperature distribution within the solid and melt in the growth ampoule was calculated and used to construct an improved experimental system for growth of high quality Cd(1-x)Mn(x)Te:V single crystals.

In Phase II of this SBIR program Brimrose has researched, designed, and built a miniature solid-state biosensor module based on an acousto-optic tunable filter (AOTF) and embedded into an optical immunodetection system. It offers the combined advantages of compact size, lightweight, low operating power, long life time, ruggedness without moving parts, high speed with random wavelength access capability and zero tuning hysteresis. In addition, Brimrose has conducted in depth investigations, both theoretical and experimental, of Integrated-Optic AOTF (IOAOTF) structures for biosensor applications. The final comparative analysis of performance characteristics of both integrated-optic and bulk AOTFs had revealed significant advantages of the bulk one both in throughput and spectral tuning range. This resulted in the selection of the bulk type AOTF as the spectral selective element of the optical biosensor module embedded into the immunosensor system. Applications for this product include: general fluorescence spectroscopy; biochemical engineering and biotechnology; remote sensing; industry process and quality control; monitoring of analyte concentrations in experimental animals and in cell cultures; and water monitoring of environmental pollutants and contaminants.

We have developed and produced vanadium doped cadmium telluride (CdTe:V) crystals that exhibit the necessary properties for optical power limiting at near infrared wavelengths. The CdTe : V crystals that we have produced exhibit the field shielding effect, have good transmission of low intensity radiation and display high photoconductivity. We have demonstrated the use of these crystals for EOPL at 1.O6 micrometers. Furthermore, through device modelling and theoretical calculations, we have developed an innovative design to improve the performance of electrooptic power limiters: the two stage EOPL. A two stage EOPL could extend the range of input intensities over which the limiter can operate and improve the dynamic range by three orders of magnitude. We present the theory behind a two stage EOPL, a prototype design of this device, as well as a preliminary evaluation of its performance. A two stage EOPL device represents a new state of the art in EOPL performance. The EOPL material and device developed during this work have potential uses in both military as well as commercial applications. Commercial applications include two dimensional signal processing, increasing the dynamic range of sensors and civilian security systems.

Novel concepts of near-collinear/collinear acousto-optic interactions have been investigated during this SBIR Phase I program. As a result, several new acousto-optic tunable filters have been built and tested. The program is highlighted by: (1) Design, fabrication and experimental demonstration of a novel TeO2 near-collinear acousto-optic tunable filter has been designed, fabricated and tested. The device exhibits a 1.29 nm spectral resolution and a 160 mw RF drive power at 1523 nm. (2) Design, fabrication and experimental demonstration of a novel polarization insensitive TeO2 near-collinear acousto-optic tunable filter. For random input light, an overall insertion loss < 3 dB has been achieved. (3) Design, fabrication and experimental demonstration of a novel collinear acousto-optic tunable filter. The filter exhibits a spectral resolution of 1.12 nm 1523nm with a low insertion loss. (4) The commercial spin-off also has been accomplished at the end of the program. A commercially available fiber pigtailed near-collinear AOTF is shown in the photo. Commercial sales have been generated and new AOTFs have been delivered to customers for applications in optical fiber communications and sensors.

The objective of this study was to produce bulk high Tc superconductor YBa2Cu3O7-x with microwave conductivity at least as good or better than that of copper. The subsequent aim was to fabricate cylindrical wave guide using this material. The ultimate goal of this study is to produce YBa2Cu3O7-x with microwave conductivity exceedingly higher (at least two orders of magnitude better) than that of copper. In principle, this is possible if the microstructure of the superconductor material is carefully controlled. The above-stated goal could be easily achieved if the large single crystals of YBa2Cu3O7-x are available or if the inside surface of a suitable substrate material in the form of hollow cylinder, could be coated with the superconductor material of high quality. The former approach, currently, seems to be far from practical realization.

Factors affecting the stability of energetic materials are not well understood. Knowledge of these factors is essential for the predictability and hence the successful applications of energetic materials as explosives and/or propellants. This in turn involves study of energetic reactions and reaction parameters. The effects of lattice defects, particle size, temperature, radiation and mechanical impact on the initiation and subsequent propagation of solid-state decomposition reaction have been studied by several researchers. However, the identification and understanding of factors governing energetics in these reactions is not achieved as of yet. This problem in our opinion can be understood in terms of the microstructure of these materials. This report focuses on the study of microstructure of energetic materials using novel non- destructive, non-intrusive x-ray diffraction techniques developed at Brimrose.

This research program was to develop a digital and automated x-ray topographic technique for use a rapid quality control tool in characterizing 3' GaAs wafers. The conclusions show that the DARC topography system is a tool capable of providing users with the information needed to characterize production III-V and II-VI semiconductor wafers. jg