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This is the first quarterly technical progress report for the Intelligent Bandwidth Compression (IBC) program (DAAK70-78-C-0148). The report describes the results of the first three months of a seven-month technical effort to develop techniques and algorithms for achieving a 1,000:1 bandwidth compression in image data transmission rate for RPV applications. The period covered by this report is 1 November 1978 to 31 January 1979. (Author)

The scalar product (SP) formulation evaluates the boundary free energy sigma using the properties of only the two homogeneous phases (without explicitly calculating the boundry profile) that meet at the boundary. The SP method is explored in detail and is now considered ready for further use. The boundary profile can be calculated using the sum method. How to formulate this method using the cluster variation method (CVM) and the natural iteration method (NIM) is presented.

The study of injection-laser mode locking was continued. The lasers were operated in the external cavity configuration using a piece of optical fiber. Pumping injection lasers with short electrical pulses at a frequency corresponding to the round-trip transit frequency of the cavity generated stable optical pulses. A modified GaAs FET structure was designed such that efficient optical coupling to the active region of the device causes a strong optical-microwave interaction in the device for high-speed optical detection, optical injection locking of oscillators and optical-microwave mixing in amplifiers. Liquid phase epitaxial growth was used to grow the necessary GaAs and Ga0.6Al0.4As layers on a semi-insulating substrate. Device fabrication is still in progress. Preliminary results showed that the devices exhibited a reasonable source-drain current versus source-drain voltage characteristic and are quite uniform over the entire wafer. A GaAs Gunn diode was designed and fabricated during the quarter. The diodes will be used to study the interaction between the injection laser's output and the high field Gunn domain in the diode. The ultimate goal is to achieve the efficient high-speed pulsed modulation of injection lasers. Diodes with various lengths were fabricated and tested using a curve tracer. Differential negative resistance was observed in all the diodes tested.

Silicon-germanium alloys in the range of 10 at .% germanium have been prepared and investigated. The object of the program is to prepare intrinsic Si-Ge with high enough absorption at 1.06 micrometers to be suitable for detectors at that wavelength and to investigate whether the changes in energy levels and optical properties of doped Si-Ge offer advantages for monolithic focal plane array applications over the corresponding doped silicon. The first year's work concentrated mostly on growing intrinsic material. After some attempts to prepare crystals by growing a succession of seeds of increasing Ge content, we found that alloys with greater than 10% Ge could be grown by the Czochralski technique directly from 0.5% (or even 0%) Ge seeds if a suitable growth rate was chosen. The necessary slow growth rate to achieve single crystals necessitated long exposures of the melt to contamination from the crucible, but the use of high-purity synthetic quartz crucibles reduced the uptake of electrically active impurties. Measurements on alloys that were not intentionally doped yielded values for the shift in the energy level of boron from the case of a pure silicon host that were in agreement with the literature.

A 37-element beryllium deformable mirror has been built, characterized, and incorporated into a Coherent Optical Adaptive Technology (COAT) system. Individual actuator deformation sensitivities of 0.2 micrometer/150 V have been measured. Mirror resonance data has been obtained indicating usable frequency ranges up to 30 to 40 kHz. Strehl ratios approaching 80% have been measured for system defocus with COAT-off to COAT-on peak irradiance of 10. (Author), See also AD-A035 150.

Under this program, we have successfully developed the ultrasonic impact grinding technique for the fabrication of aspherical geodesic lens depressions. The lens radius is 4 mm and the depth is 1.374 mm. 15% of the lens aperture is allocated for a curved rounding at the edge of the depression. The designed focal length is 10.2 mm for an aberration free aperture of 6.8 mm. The technique of ultrasonic impact grinding is proved to be precise, fast and economic. Reproducible results can be easily obtained. The tool wear problem can be neglected if more than two tools are used for grinding the lens. We have demonstrated that depth variation within 7.5 micrometers for 5 depressions can be obtained using two tools. One of the 5 depressions has the exact designed depth. The consistency of the lens depressions can be further improved if a third tool is used. The grinding process is fast using the 200 W Bullen machine. It takes onlt 45 sec. to grind a 1.4 mm deep, 8 mm diameter depression in LiNbO3 substrate.

Multidither adaptive optics systems are vulnerable to interference caused by the motion of a speckle pattern across the receiver aperture. This program investigated various techniques for reducing or canceling this interference. Several concepts were studied. A very promising one, which we call ASPECT II, was demonstrated with an experimental laboratory COAT system. Computer simulations and experimental data show that with ASPECT-II it is possible to almost completely restore speckle degraded performance of multidither COAT systems. An extensive analysis that explicitly illustrates how speckle effects interfere with COAT operations has been developed. It shows that the primary effect is to amplitude modulate the usual point source intensity distribution reflected from a target glint. With large targets, there is also an additive noise contribution from the receiver spatial intensity variations associated with reflections from the area surrounding the target focal spot. This analysis is also used to explain the operations of the ASPECT-I and ASPECT-II speckle cancelation schemes. Experimental data showing ASPECT cancelation of simulated speckle modulations is presented. The experiments show that the laboratory ASPECT system can cancel single-frequency and broadband modulations within the COAT dither band.

During this contract, we accomplished the following major tasks toward the development of a CCD liquid-crystal light valve. We have demonstrated a fully operational CCD LCLV with a contrast ratio of 50:1 and a spatial resolution of 12 lines across the device. An alternative chip dicing method has been developed that reduces degradation to the substrate by a factor of 100. In addition, a new CCD LCLV packaging technique has been developed that improves the light valve fabrication yield from 30% to 80%. (Author)

This report contains a survey of the properties of Josephson-effect devices and an evaluation of their potential utility in Naval surveillance and communication systems. Emphasis was placed on finding an existing system that could be retrofitted to improve performance. The study focused on receiver front-end characteristics and signal-processing applications. Recommendations were made for the development of a superconductive front-end for millimeter-wave applications or the development of an integrated high-speed signal-processing capability. (Author)

The function of the crossed-field closing switch has been studied over a wide range of variables. It appears that the switch behavior is more complicated than originally expected. Three different modes of conduction have been observed: the conventional crossed-field discharge, a hybrid hollow-cathode discharge, and vacuum arcs. Depending on the amplitude and duration of the current, conduction may typically pass through these modes in the above sequence. The crossed-field closing switch may be triggered magnetically or by grid control into a number of states with varying levels of voltage drop. Conduction may be allowed in the reverse direction or prevented. The present design is limited in response speed and repetition rate by the inductance of the grid and anode leads, the lack of efficient pressure control, and the need for a pulsed magnetic field., See also AD-A065 431.

The results of an extensive experimental study of mode locking in semiconductor lasers with different external-cavity configurations are described. The generation of GaAs laser pulses less than 200 psec wide at approximately-GHz repetition rates was achieved by operating the laser in a 5-cm-long external cavity. The presence of a strong resonance at low frequencies in the laser actually aided the generation of short pulses. A novel external-cavity configuration using a piece of optical fiber is also described. Modulation frequencies as high as 4.26 GHz were obtained for lasers biased only slightly above threshold, and optical pulses as narrow as 200 psec were generated using this technique. A theoretical study of the response of GaAs FETs under optical illumination was presented. For a strong photo-transistor effect to occur in an FET requires that the region of active channel under the gate electrode be illuminated. A modified FET design suitable for this purpose is proposed and analyzed. (Author)

New concepts in wide field-of-view (approx. f/0.5), very narrow band (approx. 0.1 A) optical filters in the blue-green spectral region are sought for submarine receivers in the Navy OPSATCOM laser communication link. This program was an attempt to extend the current state of the art by exploring novel techniques that would lead to improved, useful receiver filters. Of the six general approaches investigated, two were considered principal candidates: the electrooptic iso-index coupled-wave filter, and nearly degenerate four-wave mixing. It was shown that a coupled-wave electrooptic filter exhibits a theoretical 2pi field of view (FOV) and a passband of 0.2 A at 4970 A using a 1-cm sample of AgGaS2. Tunability above and below the resonant wavelength was also shown to be feasible. The four-wave mixing approach also has a 2pi FOV and, with adequate pump power, can exhibit gain. Very narrow optical bandwidths (approx. 0.08 A) and maximum skirt rejection were demonstrated theoretically. The latter approach has the biggest potential payoff but the highest risk, while the coupled-wave EO technique is basically very simple, limited only by materials availability. (Author)

The principal dopant studied under this contract is Si (n-type). Topics covered in this report include (1) encapsulation technology, (2) transferability of Si implantation technology using plasma-deposited 'silicon nitride, encapsulation, and (3) problems associated with performing channeling into (110) crystal axes of a (100)-oriented GaAs wafer. (Author)

The LMPV is a mercury-cathode, triggered, closing switch which employs a small area mercury pool and a cooled (-30 C) condensing surface to maintain the conditions for vacuum arc operation. These conditions result in high-voltage capability, fast recovery and high current operation with negligible cathode wear. Therefore, the LMPV was considered to have potential as a high average power closing switch for modulator applications. An LMPV closing switch (LMPVCS) was built at Hughes Research Laboratories and evaluated at ERADCOM at voltages up to 150 kV, currents up to 8 kA peak and 7.5 A average, pulse lengths up to 50 microseconds, and repetition rates up to 250 Hz. The device failed as a result of excessive anode dissipation caused by a long anode fall time on the order of 5 microseconds. Subsequent experimentation has indicated that the fall time is reduced at increased mercury vapor pressures, however, experiments are required to define the relation between the fall time and voltage hold-off capability. (Author)

Low-temperature epitaxial growth of Si by the solid-phase epitaxy (SPE) process has been studied to determine the effects of contaminants upon the growth process. The major sources of process-induced contaminants in SPE have been reviewed, and methods for eliminating or minimizing these have been developed. We show that under clean conditions an evaporated (amorphous) Si film will crystallize epitaxially on a Si(100) substrate when heated to 525 C, but that the growth is very sensitive to inhibition by atmospheric contaminants. Similarly, SPE growth in the system Si/Pd2Si/Si(A) has been found to proceed very differently under clean conditions as compared to the standard processing used in previous work. This difference is tentatively attributed to affects of contaminants on the Pd2Si interlayer, not on the Si(a) film as was previously believed. (Author)

The feasibility of achieveing optical injection locking of millimeter-wave IMPATT oscillators was investigated by calculating the efficiency of subharmonic optical injection locking of IMPATT oscillators. Calculations were carried out by adding a time-varying reverse saturation current term, which was generated by the incident optical signal, to the IMPATT avalanche equation. The results indicated that a locking range on the order of 100 MHz could be achieved for X-band IMPATT oscillators if modulated optical signal was converted into rf photocurrent efficiently. The injection-locking characteristics of X-band Si IMPATT oscillators were further investigated by measuring the locking range as a function of locking gain. Subharmonic locking was used with a frequency ratio ranging from 3:1 to 8:1. It was observed that a locking range of several megahertz was achievable with an oscillator at 8.11 GHz. It was also noted that even subharmonic locking was preferred over odd subharmonic locking for our oscillators.

The reliability of three types of low-noise GaAs field-effect transistor (FET or MESFET) was investigated. Types A and B incorporate Al Schottky-barrier gates; Type C has a 'gold' gate structure (Ti/Cr/Pt/Au). FETs were tested to determine the ability of their gates to withstand electrical stress. Catastrophic failure occurred at approximately 3 ergs and 0.8 ergs input energy for positive and negative dc pulses, respectively; contrary to other reports, the Au-gate devices were not more robust. With either cw or pulsed rf stress, the Type-A devices failed at between 1 and 3 W. Constant-stress accelerated life tests were performed at temperatures between 200 C and 245 C, using both unbiased and dc-biased samples. The biased gold-gate devices failed relatively early because of electrical degradation of their gates. The Type-B devices, with Au-Ge/Pt Ohmic contacts, failed because of increasing parasitic resistance; they failed faster than the Type-A FETs, with Au-Ge/Ni contacts. The biased Type-A samples failed because of structural changes in the Al gate; a poor SiO2 glassivation layer is suspected to be the cause. (Author)

The objective of this program is two-fold: (a) study of channel waveguide formation in LiNbO3 and LiTaO3 by Ti metal diffusion including Li2O out-diffusion suppression and lateral diffusion suppression; (b) development of three-dimensional channel waveguide horns designed to provide higher end-fire coupling efficiency to large-core single-mode fibers. As a result of 1976 IR and D effort, we have developed a technique to eliminate Li2O out-diffusion waveguide by annealing the crystal in LiNbO3 powder. Under this program, a series of experiments were carried out to study the temperature and time dependence of this powder treatment. Three significant results were obtained. First, it is confirmed that up to 1% molecular weight of Li2O can be brought into the substrate surface layer through the powder treatment. Second, the compensation process (Li2O in-diffusion) may occur at temperatures 750 C or lower. Third, 80% of the compensation process can be obtained in one-half hour when the annealing temperature is 900 C. The fast reaction rate implies that the powder treatment may not be dominated by the diffusion process. Solid-solid surface reaction may play an important role in this process. Single-mode channel waveguides in LiNbO3 for this program were fabricated by diffusing Ti channels into Y-cut LiNb03 wafers.

Planar TELDs have been designed, fabricated, and tested. Computer models have been developed for designing and predicting the characteristics of TELDs as a function of device geometry, material parameters, and bias conditions. TELDs have been fabricated on ion-implanted LPE and VPE GaAs. Devices with as high as 24% current drop back in the I-V characteristics have been measured, and frequency dividers that divide the input signal by any integer from two through nine have been realized. (Author)

The Rocket Model (RM) Satellite Positive Ion Beam System (SPIBS) instrument was built to be one experiment in an Astrobee F Rocket scientific payload. The purpose of the rocket experiment was to obtain electrostatic charging data in the altitude range of 100 to 300 km. SPIBS provides a controllable means of ejecting a positive xenon ion beam or a neutralized ion beam at ion energies of 1 or 2 keV. Rocket flight test results showed that surface potentials of several hundred volts were achieved by ion ejection and that charging varied as a function of altitude. Although the RM-SPIBS was built for its own distinct purpose, an equally important function of the rocket flight was the evaluation of the SPIBS design. The SPIBS primary development effort was in fact carried out under the main program. The RM-SPIBS instrument was built to a quality level similar to the SPIBS engineering model (EM) instrument.

The design and fabrication of a GaAs FET microwave oscillator was described. The optical injection locking property of this oscillator was studied. It was also found that the frequency jitter of the oscillator output could be reduced through optical illumination. A novel scheme of microwave mixing in a GaAs FET amplifier was demonstrated, where the local oscillator signal was introduced through optical injection. A new approach of obtaining optical injection locking of oscillators was developed where a FET amplifier was connected to the oscillator to be locked and the modulated laser beam was used to illuminate the amplifier instead of the oscillator directly. The merits and disadvantages of this technique was discussed. The direct amplitude modulation speed of a single mode GaA1As injection laser was found to be at least 6 GHz. The output power versus input current characteristics of the same laser was determined to be better than -40 dB in second harmonic distortion. (Author)

The Satellite Positive Ion Beam Systems (SPIBS) program was initiated by the Air Force Geophysics Laboratory (AFGL) Aeronomy Division with the long-range objective of operating an ion-ejection instrument on the Air Force SCATHA (Spacecraft Charging at High Altitude) satellite. This report describes the development details for breadboard, engineering, and flifght models of the SPIBS instrument. A fourth model, a rocket model SPIBS, was built for use in a rocket charging experiment. This report provides a description of all phases of the SPIBS instrument development process and the key technical difficulties and successes. Corroborative results obtained by AFGL personnel using the delivered instruments are referred to as appropriate to support the most significant conclusions.

An experimental program was conducted to study and improve the achievable holographic index modulation in dichromated gelatin suitable for producing high-quality holographic optical elements. Emphasis was placed on gaining a working knowledge of the chemical and physical processes involved in dichromated gelatin image production. The largest improvement in index modulation was achieved with the application of dicarboxylic acid salts. Index modulation could be increased by up to 150% per unit of light exposure over conventional processing methods by taking advantage of unipointly attached reduced chromium complexes. We confirmed the usefulness of the sol temperature as a measure of bulk cross-linking in gelatin. With polycarboxylic acids, index modulations of 0.16 were obtained in reflection holograms.

Optical illumination of solid-state microwave devices is a promising method of controlling high-power microwave signals at high speed. Microwave generation, switching, and oscillator injection locking by optical means have been demonstrated. This program, a study of the physics of semiconductor devices under optical illumination, has the specific goals of achieving optical injection locking of oscillators, demonstrating millimeter-wave modulation of injection lasers through mode locking, reducing AM and FM noise in solid-state oscillators by optical illumination, and developing new optical and microwave devices with optimal optical-microwave interaction characteristics. A feasibility study of optically injection locking a millimeter-wave IMPATT oscillator is described. The role of the IMPATT diode's nonlinearity in determining the overall efficiency of the optical injection locking process is discussed. Possible methods of obtaining suitable optical sources for subharmonic optical injection locking of millimeter-wave IMPATT oscillators are suggested. The experimental results of optical injection locking of X-band Si IMPATT oscillators are summarized. A Si IMPATT oscillator of frequency approximately 8.75 GHz was phase locked to a signal generator tuned to approximately 2.9 GHz.

This program investigated input-output coupling techniques capable of providing full duplex operation on a single strand, multimode fiber waveguide; used the optical time domain reflectometer (OTDR) to determine fiber attenuation characteristics; investigated the steady-state mode-mixing phenomena of a 4-km length of graded-index fiber; improved the OTDR; and developed low-insertion-loss bi-directional access couplers for multimode fiber waveguides.

This report summarizes research results from a program directed toward developing scene-analysis technology to deal with the problems of scene-analysis organization, control, and low-level feature extraction. The work on organization and control has concentrated on the use of a production system framework. To understand the limitations of production systems in building scene-analysis systems, both a high-level and low-level vision system were implemented. The performance of these systems is described in terms of ease of modification, ease of programming, and ability to embed appropriate domain-dependent knowledge. Several low-level feature-extraction techniques have also been developed concurrently on this program. These include an evaluation of edge operators, use of texture statistics, a glancing operator based on texture properties, and a representation for range motion. A summary is included that places these results in perspective with current work in scene analysis. (Author)

The development of a technique for the determination of the geometrical characteristics of a taper pulled in a fiber is described in this report. This technique uses the deflection of a light beam due to the taper. The insertion loss of a taper has been experimentally investigated as a function of the modal index of the fiber both with the taper immersed in air and a high index fluid (diiodomethane). The results of these experiments show that the higher order modes are more easily out-coupled by the taper than the lower order modes.

One-micron-thick films of InP were epitaxially deposited onto single-crystal InP substrates at about 400 deg C by the planar reactive deposition technique. Scanning electron microscope measurements show that smooth surfaces are obtained on (100) substrates, and shingled surfaces are obtained on (III) substrates. Mass spectrographic analysis indicates that the purity of these films is about 10 parts per million atomic. Electrical evaluation of these films deposited on semi-insulating substrates shows that at room temperature the films are n-type with electron concentrations as low as 10 to the 16th power/cu cm and mobilities as high as 1350 sq cm/V sec. (Author)

The purpose of this contract was to further the development of the Hughes Rotating Gravity Gradiometer (RGG). The scope of effort was limited to studies and performance tests and demonstrations in the laboratory environment. Two RGG sensors were involved. The first, RGG-1, was built in 1974 and 1975 under the prior contracts. The second, RGG-2, was designed and built during the course of this contract. The initial scope of work included various tasks to test and modify RGG-1, with the goal of determining configuration changes to be incorporated in RGG-2. Specifically, the performance results obtained with RGG-2 demonstrate that: the design goals have been met for thermal and electronics noise; the sensor output noise goals have nearly been met for the vertical spin axis orientation; considerable optimism is warranted that the sensor output noise goals can be met for the horizontal spin axis orientation; and continued development is both necessary and warranted. In summary, the availability of a platform and the performance success of RGG-2 permit immediate consideration of a follow-on program which would test and demonstrate all the components of a gravity gradiometer system. It is the recommendation of this report that the Hughes RGG sensor be integrated with a platform at the earliest possible time, and tested in the laboratory environment. It is also the recommendation of this report that the RGG-1 sensor be retrofitted up to the RGG-2 configuration to permit simultaneous development and test efforts., Continuation of contract F19628-72-C-0222 and Contract 19628-75-C-0201.

Wafer processing techniques have been developed to allow fabricating an n-MOS clamp-sample-and-hold (CSH) circuit suitable for detecting outputs from charge couple device shift registers operating at 25 MHz. The techniques developed include methods to define circa 1 micrometers device features using electron beam lithography as well as the methods of wafer processing to make functional MOSFET devices at these dimensions. In addition, the CSH circuit was designed and thoroughly simulated with computer models. The development work required determining techniques to etch fine structures in thin films of silicon nitride and polycrystalline silicon. Data were also obtained of the amount of underoxidation when a silicon wafer is oxidized using silicon nitride masking features. Methods were also developed to provide 400 A gate oxides, shallow n(+)p junctions, and reliable contacts to these junctions without metallization spiking. Several diagnostic chips were designed and fabricated. Experience with these provided a list of design rules for the fabrication, in general, of circuits using the high resolution nitride masked oxidation process. It also provided a list of device performance parameters. (Author)

The objective of this program was to develop a high-data-rate-low-power modulator for doubled Nd:YAG applications with Gigabit/sec data rate capability, 3 W drive power and capable to handle 0.5 W cw power (3.3 W peak) using integrated optics techniques. An approach to the development of this modulator has been defined. Most notable is the demonstration of optical power handling capabilities of Ti diffused LiTaO3 waveguides of 300 mW with no damage and no power saturation. Prism coupling efficiency of 55% input and 80% output have been achieved. The waveguide losses at 5145 A have been measured to be 5 dB/cm. Single mode and multimode waveguides have been found by the in-diffusion process. The nature of the optical waveguide damage at room temperature and at elevated temperatures (approx 150 C) has been studied. The high optical power densities sustained by these structures were accommodated by high temperature operation of the waveguide structures. Preliminary experiments on Bragg deflection have also been carried out. (Author)

The exploratory development program described in this report had as its basic objective the provision of antireflection thin films or thin film systems for single crystal and polycrystalline alkaline earth fluoride laser window materials. The films must be of sufficiently high optical quality and uniformity to satisfy the constraints imposed by use as coating materials in high-power infrared DF and CO laser systems operating in the 2 to 6 micrometer region. In addition, they must have sufficient ruggedness to survive the environmental conditions expected in such an operation. Since the performance of the deposited film systems, and therefore of the finished coated window, is critically dependent on substrate quality, an important part of this program was the development of adequate substrate polishing, cleaning, and handling procedures. Because windows approaching 1/2 m in diameter may be required in the future, both the substrate preparation and the thin film deposition techniques were established with a sufficiently high degree of reproducibility and quality control so that the technology could be and was successfully scaled-up and transferred to an operating division after a short developmental period.

This report summarizes a three-year investigation into the absorption losses in thin film coatings and surfaces of highly transparent materials at 3.8 microns. The primary emphasis during the first two years was on the minimization of thin film coating losses with the result that it is now possible to achieve film absorptions at DF laser wavelengths of nearly 0.01%/surface. In addition, attenuated total reflection studies performed in cooperation with the Naval Research Laboratory yielded information on the nature and cause of surface absorption in highly transparent coatings and bulk materials. The majority of this report is devoted to additional studies on surface absorption and methods that might be used to harden the surfaces of transparent materials. Surface absorption was measured in KCl and CaF2 that had been selectively contaminated by either H2O, D2O, C2H5OH, CH3OH, or NH4OH. Although increases in surface absorption of as much as 100% resulted for hydrocarbon contamination, a smaller increase than expected resulted for H2O and D2O contamination. The surface hardening experiments involved measuring delayed failure in coated (Al2O3) and uncoated SrF2 and CaF2 substrates. No definitive conclusions could be drawn regarding these results because the starting static loads were too high. All the tests were not completed.

Theoretical and experimental studies of direct-current modulation of semiconductor injection lasers were carried out. The small-signal modulation frequency response of a single-mode laser was measured and found to agree well with the calculation result. Direct modulation of a single-mode laser up to 6 GHz was achieved. Experiments on optical injection locking of a transistor oscillator were carried out. Injection locking was achieved not only at fundamental frequencies but also at various subharmonics with less tolerance in frequency deviation. It is also possible to perform simultaneous switching and phase locking in these oscillators. We have also succeeded in phase locking a GaAs FET oscillator at 7 GHz with an injected optical signal modulated at 3.5 GHz. A novel scheme of carrying out microwave mixing in GaAs FET amplifiers was demonstrated in which one of the signals is fed into the input port of the amplifier while the local oscillator signal is introduced through optical injection and the mixed signal is taken from the output port of the amplifier. Experimental results on the optical switching of GaAs IMPATT diode oscillators is presented. The IMPATT microwave output power can be either enhanced or reduced depending on the bias condition and the microwave cavity tuning.

In the last few years, several low optical absorption 10.6 micrometer AR coatings for KCl have been developed at Hughes Research Laboratories (HRL) and at other laboratories. The objective of this program was the development of 9.27 micrometer AR coatings which have a film absorption loss of less than 0.01% and a reflection of less than 0.1% per surface. The achievement of the program objective will permit the development of a 9.27 micrometer AR coating for a 32.5 cm diameter polycrystalline KCl window. Because previous studies had shown that castings deposited under ultra-high vacuum (UHV) conditions had lower absorption losses than did coatings deposited in conventional vacuum systems, the present study was limited to UHV-deposited films. Mass spectrometer analysis had shown that impurities were evolved occasionally during the evaporation of film materials. As a consequence, residual gas analysis (RGA) was performed to ensure that impurities were not present in the system. Also if impurities were located in the film materials, either they were removed by reactive atmosphere processing (RAP) or techniques were developed to prepare clean material.

Single crystals of calcium fluoride and strontium fluoride double doped with Na+ and Ce3+ were czochralski grown using RAP (HF) to maximize anion purity. (Author)

Three major issues in the development of a multimode liquid-crystal light valve were addressed in this phase of the continuing research; Liquid-crystal electro-optical effect, Light valve stability and lifetime, and Photoconductor performance. We concluded that the lifetime and stability of the tilted perpendicular alignment cannot be sufficiently improved to produce a practical and useful device for a high-brightness, large screen display system. The problem is that the molecular pre-tilt angle is unstable in the presence of a high-brightness projection light. The tilted perpendicular alignment therefore was abandoned in favor of the 45 deg. twisted nematic alignment using the hybrid field effect mode (HFE mode), by HRL. With respect to color symbology and multimode operation; however, the HFE mode was less suitable, and considerable experimentation with the goal of optimization was performed and is reported here. A phenomenological study was made on liquid-crystal cells operated in the HFE mode. The objectives were to optimize and to determine the range and intensity of colors that can be obtained with an HFE light valve and to acquire a working knowledge of the effect of certain cell parameters (e.g., twist angle, thickness, and the match or mismatch of the polarization plane with front surface alignment).

The principle dopant studied under this contract is Si (n-type). Topics covered in this report include: (1) encapsulation technology; (2) transferability of Si implantation technology using plasma-deposition 'silicon nitride' encapsulation; and (3) problems associated with performing channeling into (110) crystal axes of a (100)-oriented GaAs wafer. (Author)

The theory of Ubitrons (Undulating Beam Interactions) for high power millimeter wave amplification is reviewed and extended. Relativistically correct dc and small-signal theories are developed and applied to a 94-GHz, 50-kW Ubitron amplifier., Includes Errata sheets dated May 77.

Theoretical calculations were carried out to explain the observed results of optical switching of GaAs IMPATT diode oscillators. In the previous experiments it was found that depending on the diode's bias condition, the frequency of oscillation, and the intensity of illumination, the IMPATT microwave output power could be either enhanced or reduced. This problem was treated by carrying out a theoretical calculation of the property of IMPATT diode under optical illumination. It was determined that the most significant contribution of optical illumination in an IMPATT diode is the drastic increase in reverse saturation current Is. Using small signal analysis we obtained an expression for the total impedance of the IMPATT diode under optical illumination. It was found that optical illumination causes the shifting of the negative resistance and reactance versus frequency curves. This in turn causes the oscillation frequency to vary and the output power to drop in general. However, the cavity tuning yields a strongly frequency dependent threshold for the diode. Therefore under certain circumstance optical illumination can actually trigger the IMPATT diode into oscillation also. (Author)

The development of a reflective mode liquid crystal light valve suitable for large screen dynamic color symbology projection display is described. The light valve consists of a sandwich structure of a thin film photoconductor, light blocking layer, broad visible spectrum dielectric mirror and liquid crystal sandwiched between two glass electrodes with transparent conductive electrodes. There are no matrix elements to define resolution because of the insulating characteristics of the dielectric mirror it is necessary to use ac voltages to operate the light valve. The report details the development of the ac light valve with two liquid crystal modes; tilted perpendicular, birefringent field effect and hybrid field effect (HFE). The development of the light valve proceeded in two phases. The first phase concentrated on the tilted perpendicular device. The development of liquid crystals and alignment techniques, CdS photoconductor development, dielectric mirror fabrication, and light valve device physics are detailed here. Also reported are substrate uniformity and cosmetic quality improvements, and a new cell holder design. Finally, the performance of the two tilted perpendicular light valves, delivered to the Naval Electronics Laboratory Center, San Diego, California, is described. The second phase continued the work of the first phase but concentrated on the HFE light valve. The application of the HFE mode to color symbology is described. Finally, at the end of this phase the performance of the HFE color symboloby light valve that was the final device delivery to NELC is detailed.

The Satellite Positive Ion Beam System (SPIBS) instrument is being developed as a charge ejection payload for the Air Force Satellite P78-2 (Satellite Charging At High Altitude). SPIBS will allow controlled ejection of xenon ions as part of the systematic investigation of satellite charging. Ion Beam currents of about 0.3 and 1.0 mA are obtained at a beam voltage of 1 kV; currents of about 0.7, 1.4, and 2.0 mA are obtained at 2 kV. Redundant filament neutralizers are provided to allow full or partial beam neutralization and an independent source of electrons. These neutralizers can be biased at ten levels from -1 kV to +1 kV with respect to satellite ground. This paper describes the engineering model design, and presents ion source, expellant, and power processor test results. (Author), Presented at AIAA International Electric Propulsion Conference, held at Key Biscayne, Florida, 14-17 November 1976.

Theoretical and experimental studies of direct current modulation of semiconductor injection lasers were carried out. In the small signal approximation we found that the maximum usable frequency of modulation was limited to under 10 GHz. Experimentally we have demonstrated modulation of a single mode laser up to 3.4 GHz and was currently limited by our detection system. Optical injection locking experiments were carried out at low frequencies (2GHz). Injection locking was observed not only at fundamental frequencies but also at various subharmonics with less tolerance in frequency deviation. It is also possible to achieve simultaneous switching and phase locking in these oscillators. (Author)

Research was conducted into the minimization of optical absorption in low-loss window and coating materials for use in high-power DF chemical lasers. Candidate coating materials that were investigated as single-layer, half-wave thick films at 3.8 micron include PbF2, ThF4, ZnSe, Si, MgO, Al2O3, LiF, and NaF on CaF2 substrates. Of these, the fluorides have the lowest absorption losses and the Si and oxide films have the largest. A thorough study of extrinsic absorptions in ThF4 and ZnSe films on CaF2 was performed in conjunction with NRL using attenuated total reflection spectroscopy. ZnSe films showed considerably less OH(-) absorption than did the ThF4 films. (Author)

During the third quarter of this program, the measurement of single mode coupling efficiency for linear tapers of four different taper lengths was continued. For TM wave propagation, the coupling efficiency was much lower than for TE wave propagation. The difference in coupling efficiency was due to the presence of Li2O out-diffusion waveguide modes, which occurred only when the TE mode was excited in Ti-diffused channel guide. The coupling efficiency of a given taper structure depends strongly on the expansion ratio of the channel width (final width to initial channel width). So it is important to know the amount of lateral diffusion which proceeds simultaneously with the downward diffusion. We have studied the Ti concentration profile near the edge of a stripe of 70 microns initial width using electron microprobe technique. The lateral spread of this 70 microns wide channel guide was about 6 micrometers on each side. We concluded that enhanced lateral diffusion was not observed in this study.

The preliminary testing and the design of crossed field closing switches for use at an average power of 0.48 MW are described. This work is directed towards a full power demonstration at 40 kV, 20 kA (10 microsec pulse width) operating at 125 Hz and an average current of 24 A. The key feature of the crossed field closing switch as opposed to other spark gap switches is the randomization of the arc location on a shot-to-shot basis. This desired randomization is observed at the intermediate test levels thus far attempted with an uncooled device. A fully cooled device has been designed and is under construction. (Author), Also available as Rept. no. GIDEP-301.55.00.00-04-01.

This report, together with three previous quarterly reports, presents the design, development, fabrication and evaluation of a wideband optical switch based on the deflection of two dimensionally confined beams by electro-optically controlled phase grating. The waveguide medium is Ti-diffused LiNbO3. An interdigital electrode is placed on the overlapped region of two crossed channel waveguides. When a voltage is applied to the electrode, a Bragg phase grating is formed so that the optical beam in one channel waveguide is deflected into the opposite one. In order to interface the switching device to single mode optical fibers, 4 micrometers wide single mode channel waveguides are employed at the input and output ports. These waveguides are expanded adiabatically through slowly tapered sections into wide multimode channel waveguides (30 micrometers) that intersect in the grating interaction region.

This program represents an effort to develop a thin film optical switch using integrated optics technology. The switching of the direction of propagation of a two-dimensionally confined optical beam between two-channel waveguides is achieved using an electro-optic phase grating. The waveguiding medium is a Ti-diffused LiNbO3 layer. The coupling of single-mode guides to single-mode guides by mode expansion and compression tapers is an integral part of the switch design. (Author)

A triode version of the crossed-field closing switch (CFCS) has been successfully tested at average powers of up to 800 kW (40 kA, 40 kV, 12 microsec pulse width at 80 Hz) for burst durations of 30 sec. Unlike most conventional spark gaps, the arc is initiated from a crossed-field glow discharge and occurs at random locations on a shot-to-shot basis. This uniformly disperses the heat loading and erosion over a relatively large electrode surface area which may then be cooled. (Author)