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The analysis and design of a GaAlAs Mach-Zehnder electrooptic modulator operating at 820 nm is presented. Optical modulation is achieved through coplanar 50-ohm traveling-wave microwave electrodes with a resulting 3-dB bandwidth-length product of 11.95 GHz cm.
In 1992, NASA will conduct a Space Shuttle-based lidar experiment at the fundamental, first, and second harmonic wavelengths of a Nd:YAG laser. A second, NASA U-2 aircraft-based experiment will measure water vapor vertical profiles in the lower atmosphere. In addition, NASA plans three space-based (polar orbit-platform) observatories, incorporating laser and electrooptics technologies covering the 280-10,000 nm spectrum, which will have long service lives with minimal servicing requirements.
The present conference on the development status of IR electrooptics technologies discusses topics concerning such systems' materials and architectures, their modeling and data processing requirements, and advancements in IR automatic target recognition. Attention is given to active multispectral three-dimensional vision sensor image evaluation, a VHSIC processor-based real-time image tracker, the use of Al-alloy castings as diamond machining substrates for optical surfaces, a two-dimensional recognition range model, calculations of the optical blurring in IR systems, synthetic IR scene generation, and automatic target recognition evaluation.
An asymmetric delta-doped GaAs structure is described which exhibits novel photovoltaic effects and low-intensity nonlinear optics. Of particular interest in this kind of structure is the ability to design the electrooptical and nonlinear optical properties and the material response time over a wide range by appropriate design of the doping profile.
Losses in short-haul broadband fiber-optic links are primarily due to many characteristics of electrooptic devices. In particular, electrical mismatch at the electrical/optical interfaces have been the dominant source of loss. Losses can be significantly reduced and link performance enhanced by reactive matching of the laser and detector modules. The steps in the design of low-loss fiber-optic links are presented, which are on the basis of (1) two-tier deembedding of laser and photodiodes from test fixtures and (2) reactively matching them to a standard 50-ohm system. These concepts are demonstrated by design of a link operating at 0.5 to 1 GHz using reactively matched optical transmitter and receiver modules.
The societal and economic benefits derived from the application of aerospace technology to improved health care are examined, and examples of the space-technology spinoffs are presented. Special attention is given to the applications of aerospace technology from digital image processing, space medicine and biology, microelectronics, optics and electrooptics, and ultrasonic imaging. The role of the NASA Technology Application Team in helping the potential technology users to identify and evaluate the technology transfer opportunities and to apply space technology in the field of medicine is discussed.
In this paper, mission orbit considerations are addressed for using the Space Shuttle as a telescope platform for observing man-made orbital debris. Computer modeling of various electrooptical systems predicts that such a space-borne system will be able to detect particles as small as 1-mm diameter. The research is meant to support the development of debris- collision warning sensors through the acquisition of spatial distribution and spectral characteristics for debris and testing of detector combinations on a shuttle-borne telescopic experiment. The technique can also be applied to low-earth-orbit-debris environment monitoring systems. It is shown how the choice of mission orbit, season of launch, and time of day of launch may be employed to provide extended periods of favorable observing conditions.
Various papers on scene simulation, modeling, and real image tracking using IR imaging are presented. Individual topics addressed include: tactical IR scene generator, dynamic FLIR simulation in flight training research, high-speed dynamic scene simulation in UV to IR spectra, development of an IR sensor calibration facility, IR celestial background scene description, transmission measurement of optical components at cryogenic temperatures, diffraction model for a point-source generator, silhouette-based tracking for tactical IR systems, use of knowledge in electrooptical trackers, detection and classification of target formations in IR image sequences, SMPRAD: simplified three-dimensional cloud radiance model, IR target generator, recent advances in testing of thermal imagers, generic IR system models with dynamic image generation, modeling realistic target acquisition using IR sensors in multiple-observer scenarios, and novel concept of scene generation and comprehensive dynamic sensor test.
The present conference on airborne reconnaissance discusses topics in imagery exploitation, reconsystem modeling and analysis, and reconnaissance optics and electronics configurations. Attention is given to airborne minefield detection, the optimization of an IR linescanner for RPV operations, real-time display of IR linescanner data for RPVs, three-dimensional model-guided site recognition, the AMIDARS high-performance real-time display, and MMW sensor image analysis. Also discussed are reconnaissance concepts for the 3-5 micron spectral window, sensor concept development for hazard detection, a stabilization system for a large aperture camera, three-axis image stabilization with a two-axis mirror, the results of performance tests on the TOW target collimator design, and the replacement of film by electrooptic media in advanced tactical airborne reconnaissance.
An improved electrooptical system has been developed to sense wind tunnel model position. The original system using 25.6 mm, 1024-element linear photodiode arrays (PDAs) is being successfully used at a NASA wind tunnel but has a limited range. A new two-channel system using 61.44 mm, 4096-element PDAs has been developed to double the range of vertical and pitch measurement and increase the resolution by 60 percent. The PDAs are illuminated by expanding the beam of a single low power helium neon laser into a collimated sheet of light. An object placed in front of the two parallel PDAs produces a shadow on the array apertures which determines the object's position or size. The system has an overall precision of 12.7 microns and + or - 0.015 degrees in linear and angular measurements.
A laser-material database and laser-modeling software system for designing lasers for laser-based Light Detection And Ranging (LIDAR) systems are presented. The software system consists of three basic sections: the database, laser models, and interface software. The database contains the physical parameters of laser, optical, and nonlinear materials required by laser models. The models include efficiency calculations, electrooptical component models, resonator, amplifier, and oscillator models, and miscellaneous models. The interface software provides a user-friendly interface between the user and his personal data files, the database, and models. The structure of the software system is essentially in place, while future plans call for upgrading the computer hardware and software in order to support a multiuser multitask environment.
Theoretical and applications aspects of optoelectronic control for microwave devices are examined in an introduction for graduate engineering students and practicing engineers. The basic features of optical MMICs are reviewed, and chapters are devoted to laser diodes, electrooptic modulators, photodetectors, microwave fiber-optic links, optoelectronic switching and gating, optoelectronic microwave signal generation, an optoelectronic switch matrix, optoelectronic switching and modulation of oscillators, and optoelectronic injection-locking and tuning of oscillators. Extensive diagrams, drawings, and graphs are provided.
An electric field induced-guide/antiguide optical intensity modulator which has a very wide optical bandwidth from 1 to 1.55/micron which is the largest ever reported before for an intensity modulator. A TE mode ON/OFF ratio larger than 21 dB at 1.15 micron, and a propagation loss about 1 dB at 1.3 micron has been measured. The electrooptic effects, along with carrier effects have been exploited to increase the refractive index under the guide and adjacent antiguide electrodes by applying reverse biases to them.
Nap-of-the-earth flight mode is extremely demanding on the rotorcraft pilots. This fact has motivated the research in automating various components of low altitude rotorcraft flight operations. Concurrent with the development of guidance laws, efforts are under way to develop systems for locating the terrain and the obstacles using inputs from passive electrooptical sensors such as TV cameras and infrared imagers. A passive obstable location algorithm that uses image sequences from cameras undergoing translational and rotational motion is developed. The algorithm is in a general form and can operate in multicamera imaging environments. Performance results using an image sequence from an airborne camera are given.
The results of lidar measurements carried out on laboratory scale models of clouds are presented. Measurements on laboratory scale models are important since one has the knowledge of the relevant parameters of the diffusing medium, such as: scattering and absorption coefficients, phase function, homogeneity, shape, etc. Knowledge of these parameters enables one to use the results to test the reliability of theoretical and numerical investigations. To obtain a laboratory scaled model of a lidar system sounding a cloud, it is necessary to scale down all the geometrical quantities by the same factor to reduce distances of the order of kilometers to the order of meters, keeping the size and the optical depth of the diffusers unchanged. If a time resolution of the order of nanoseconds is necessary for a lidar sounding actual clouds, the corresponding time resolution for the laboratory model should be of the order of picoseconds. It is possible to obtain this resolution by using picosecond laser systems and fast electrooptical detectors like the streak camera. The results of the laboratory measurements showed that the multiple scattering effect strongly depends on the size of the diffusers, as well as on the concentration. The experimental results were compared with the numerical results of a Monte Carlo code. A generally good agreement was obtained.
This paper describes the Space Station Furnace Facility (SSFF) program. The SSFF is a new development intended to provide an advanced facility for materials research in the microgravity environment of the Space Station. The SSFF will be designed for research in metals, oxides, glasses, and alloy solidification and crystal growth of electronic and electrooptical materials. The facility will be designed to process multiple samples in one or more furnaces in an automated mode. The SSFF will be built around a general facility core which will provide common support functions not provided by the Space Station, subsystems which could best be centralized, and common subsystems which could be distributed with each experiment module. The SSFF will be capable of operation in both the manned and unmanned mode and is scheduled for early deployment aboard the Space Station.
A method for determining the detector electrooptical transfer function (DEOTF) at different discrete frequencies simultaneously is presented. It involves simulation of the detector with a waveform of unknown frequency composition, such as a square wave or impulse function. The DEOTF is calculated as the ratio of the discrete Fourier transform of the detector output to the transform of the input waveform. This technique was successfully applied to Golay cell and bolometer detectors and can be used for other linear detector systems.
The first experimental observation of a change in the director azimuthal angle due to applied shear stress is reported in a sample configuration involving a liquid-crystal-coated top surface exposed directly to gas flow. The electrooptic response caused by the shear stress is large, fast, and reversible. These findings are relevant to the use of liquid crystals in boundary layer investigations on wind tunnel models.