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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,135 records · Page 63
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Integrated optics technology study

The materials and processes available for the fabrication of single mode integrated electrooptical components are described. Issues included in the study are: (1) host material and orientation, (2) waveguide formation, (3) optical loss mechanisms, (4) wavelength selection, (5) polarization effects and control, (6) laser to integrated optics coupling,(7) fiber optic waveguides to integrated optics coupling, (8) souces, (9) detectors. The best materials, technology and processes for fabrication of integrated optical components for communications and fiber gyro applications are recommended.

Chen, B.↗
NASA NTRS1982

Integrated optics technology study

The status and near term potential of materials and processes available for the fabrication of single mode integrated electro-optical components are discussed. Issues discussed are host material and orientation, waveguide formation, optical loss mechanisms, wavelength selection, polarization effects and control, laser to integrated optics coupling fiber optic waveguides to integrated optics coupling, sources, and detectors. Recommendations of the best materials, technology, and processes for fabrication of integrated optical components for communications and fiber gyro applications are given.

Chen, B.↗
NASA NTRS1981

Realizable feed-element patterns for multibeam reflector antenna analysis

The radiation pattern of a feed element is approximately described by a simple function (cos theta) to the q power. For a given element spacing of the feed array, simple formulas for estimating the practical value of q when the element is an open-ended rectangular waveguide, an open-ended circular waveguide, a pyramidal horn, or a cigar antenna are given.

Rahmat-Samii, Y.↗
NASA NTRS1983

Transducer Joint for Kidney-Stone Ultrasonics

Ultrasonic therapy for kidney stones improved by new way of connecting wire-probe ultrasonic waveguide to transducer. Improved mounting allows joint to last long enough for effective treatment. Sheath and rubber dampers constrain lateral vibration of wire waveguide. Combination of V-shaped mounting groove, sheath, and rubber dampers increases life expectancy of wire 15 times or more.

Angulo, E. D.↗
NASA NTRS1982

Design, fabrication and evaluation of chalcogenide glass Luneburg lenses for LiNbO3 integrated optical devices

Optical waveguide Luneburg lenses of arsenic trisulfide glass are described. The lenses are formed by thermal evaporation of As2S3 through suitably placed masks onto the surface of LiNbO3:Ti indiffused waveguides. The lenses are designed for input apertures up to 1 cm and for speeds of f/5 or better. They are designed to focus the TM sub 0 guided mode of a beam of wavelength, external to the guide, of 633 nm. The refractive index of the As2S3 films and the changes induced in the refractive index by exposure to short wavelength light were measured. Some correlation between film thickness and optical properties was noted. The short wavelength photosensitivity was used to shorten the lens focal length from the as deposited value. Lenses of rectangular shape, as viewed from above the guide, as well as conventional circular Luneburg lenses, were made. Measurements made on the lenses include thickness profile, general optical quality, focal length, quality of focal spot, and effect of ultraviolet irradiation on optical properties.

Wood, V. E.↗
NASA NTRS1983

Guidance and control of MIR TDL radiation via flexible hollow metallic rectangular pipes and fibers for possible LHS and other optical system compaction and integration

Flexible hollow metallic rectangular pipes and infrared fibers are proposed as alternate media for collection, guidance and manipulation of mid-infrared tunable diode laser (TDL) radiation. Certain features of such media are found to be useful for control of TDL far field patterns, polarization and possibly intensity fluctuations. Such improvement in dimension compatibility may eventually lead to laser heterodyne spectroscopy (LHS) and optical communication system compaction and integration. Infrared optical fiber and the compound parabolic coupling of light into a hollow pipe waveguide are discussed as well as the design of the waveguide.

Yu, C.↗
NASA NTRS1983

Rectangular Luneburg-type lenses for integrated optics

Compact Luneburg-type lenses of rectangular outline as viewed from above have been made by thermal evaporation of As2S3 glass onto single-mode LiNbO3:Ti waveguides through suitably shaped masks and subsequent exposure of the glass to ultraviolet light. The best lenses had speeds of f/5.5 at an aperture of 10 mm and focal spots at reduced aperture about 1.2 times the diffraction-limited size. These lenses have a field of view of at least 25 degrees inside the waveguide.

Wood, V. E.↗
NASA NTRS1983

Ladder supported ring bar circuit

An improved slow wave circuit especially useful in backward wave oscillators includes a slow wave circuit in a waveguide. The slow wave circuit is comprised of rings disposed between and attached to respective stubs. The stubs are attached to opposing sidewalls of the waveguide. To the end that opposed, interacting magnetic fields will be established to provide a very high coupling impedance for the slow wave structure, axially orientated bars are connected between rings in alternate spaces and adjacent to the attachment points of stubs. Similarly, axial bars are connected between rings in the spaces which do not include bars and at points adjacent to the attachment of bars.

Kosmahl, H. G.↗
NASA NTRS1983

30/20 GHz spacecraft GaAs FET solid state transmitter for trunking and customer-premise-service application

Sixteen 30 dB 0.5 W amplifier modules were combined to satisfy the requirement for a graceful degradation. If one module fails, the output power drops by only 0.43 dB. Also, by incorporating all the gain stages within the combiner the overall combining efficiency is maximized. A 16 way waveguide divider combiner was developed to minimize the insertion loss associated with such a large corporate feed structure. Tests showed that the 16 way insertion loss was less than 0.5 dB. To minimize loss, a direct transition from waveguide to microstrip, using a finline on duroid substrate, was developed. The FETs fabricated on MBE grown material, demonstrated superior performances. For example, a 600 micrometer device was capable of 320 mW output power with 5 dB gain and 26.6% efficiency at 21 GHz. The 16 module amplifier gave 8.95 W saturated output power with 30 dB gain. The overall efficiency was 9%. The 3 dB bandwidth was 2.5 GHz. At 17.7 GHz the amplifier had 5 W output power and at 20.2 GHz it still had 4.4 W.

Saunier, P.↗
NASA NTRS1983

Multifrequency synthetic aperture radar antenna comparison study

Three multifrequency, dual polarization SAR antenna designs are reviewed. The SAR antenna design specifications were for a "straw man' SAR which would approximate the requirements for projected shuttle-based SAR's. Therefore, the physical dimensions were constrained to be compatible with the space shuttle. The electrical specifications were similar to those of SIR-A and SIR-B with the addition of dual polarization and the addition of C and X band operation. Early in the antenna design considerations, three candidate technologies emerged as having promise. They were: (1) microstrip patch planar array antennas, (2) slotted waveguide planar array antennas, and (3) open-ended waveguide planar array antennas.

Blevins, B. A.↗
NASA NTRS1984

Coupling coefficient of gain-guided lasers

An analytical model is presented for the coupling coefficient for two gain-guided coupled waveguides, e.g., semiconductor laser arrays. A common parabolic gain distribution is assumed for the lasers, and the effective dielectric constant distribution is approximated in terms of the bulk refraction index, wavelength, power filling factor, and the antiguiding factor. The fundamental mode is then formulated and used in an integral for the coupling coefficient. The dependence of the coefficient of various waveguide parameters is described.

Katz, J.↗
NASA NTRS1984

Theory of high-harmonic rectangular gyrotron for TE(mn) modes

In this paper, the linearized relativistic Vlasov equation is solved and a dispersion relation is calculated for the interaction between a relativistic electron beam and the electromagnetic fields of a rectangular waveguide supporting TE(mn) modes. The dispersion relation is simplified to the special case of a frame of reference moving with the electrons and the resulting coupling coefficient epsilon(mn)super l is calculated for various TE(mn) modes. The dependence of epsilon(mn)super l on the parity of the harmonic number l and various mn modes of the waveguide are discussed.

Ferendeci, A. M.↗
NASA NTRS1984

Rate equations analysis of phase-locked semiconductor laser arrays under steady state conditions

Rate equations analysis of phase-locked semiconductor laser arrays has been carried out. It was found that for given (laser) current densities, the photon density distribution in the array elements is that particular one which maximizes the total photon density. The results of this analysis were then combined with the waveguide properties of the laser array waveguide, yielding a basic model of phase-locked diode laser arrays. This model explains the effects of the variation of the current combination through the array elements on its mode structure that were observed recently.

Katz, J.↗
NASA NTRS1985

Hybrid Fiber-Optic/CCD Chip

Low noise and linearity of charge-coupled devices (CCD's) combined with optical waveguide components in hybrid, integrated chip package. Concept used to measure laser flux in fiber-gyro application using sensing fibers that range from several to several tens of kilometers in length. Potential applications include optical delay measurement and linear detector of light flux emanating from fiber-optic waveguides.

Goss, W. C.↗
NASA NTRS1984

Advanced infrared laser modulator development

A parametric study was conducted to develop an electrooptic waveguide modulator for generating continuous tunable sideband power from an infrared CO2 laser. Parameters included were the waveguide configurations, microstrip dimensions device impedance, and effective dielectric constants. An optimum infrared laser modulator was established and was fabricated. This modulator represents the state-of-the-art integrated optical device, which has a three-dimensional topology to accommodate three lambda/4 step transformers for microwave impedance matching at both the input and output terminals. A flat frequency response of the device over 20 HGz or = 3 dB) was achieved. Maximum single sideband to carrier power greater than 1.2% for 20 W microwave input power at optical carrier wavelength of 10.6 microns was obtained.

Cheo, P. K.↗
NASA NTRS1983

Integrated optics for fiber gyro's

Expected advantages of incorporating integrated optical waveguide components into fiber gyroscopes are summarized. The structural-simplicity benefits which can be achieved through the use of solid-state lasers, and integrated and fiber optics are examined; angular rate noise and random walk drift for the current technology in the 0.84-micron wavelength region are reported as 0.00001 deg/sec and 0.0002 deg/hr to the 1/2, respectively. The state-of-the-art in the pertinent materials research is reviewed; lithium niobate, suggested to be used as a waveguide substrate material, is noted to have a complex chemistry that is not yet fully understood. However, most of the optical and electrooptical components of a fiber gyro are conceptually understood and have been demonstrated.

Goss, W.↗
NASA NTRS1986

Buried-Dielectric-Microstrip Network

Problem of obtaining very-broadband frequency response resolved with buried-dielectric-microstrip matching network incorporated into infraredwaveguide structure. Waveguide modulator structure represents state-of-the-art of integrated optical devices: Has three-dimensional shape to accommodate three quarter-wavelength-transformers for microwave impendance matching at both input and output terminals. Microwave network, along with microstrip line designed with aid of computer, integrated with optical waveguide and used to tune line-selectable CO2 laser that provides total tuning range of 30 GHz in two sidebands.

Cheo, P. K.↗
NASA NTRS1985

Asymptotic high frequency analysis of the electromagnetic backscattering from an inlet model consisting of piecewise linearly tapered sections

Electromagnetic backscattering from an open ended three dimensional inlet model is analyzed and computed patterns are compared with results of experimental measurements. The model is comprised of two sections. The first section consists of a linearly tapered waveguide with a rectangular opening at one end and the other end is connected to the second section which is a uniform rectangular waveguide with a planar perfectly conducting termination. The model is electrically large so that many propagating modes are excited. The method of analysis contains conventional aperture integration and modal techniques combined with high frequency techniques, which employ concepts such as modal rays, geometrical theory of diffraction and equivalent currents. For the cases considered, it is shown that only a few of the many propagating modes contribute appreciably to the backscattered field. These modes are selected according to their modal ray angle directions.

Altintas, A.↗