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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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This paper reports the first use of CW room-temperature injection lasers in a scanning facsimile system. The document reader can resolve about 2000 spots in each horizontal line of its raster scan, which is close to the performance attained using an He-Ne gas laser. The results obtained thus suggest that these small, efficient lasers can replace gas lasers in many applications.
High-resolution Brillouin spectra were recorded for light scattered at small angles from liquid CS2. The use of a single-mode He-Ne laser, locked in frequency to a Fabry-Perot interferometer, permitted measurements of line widths of the order of 10 MHz for frequencies in the range 300-1000 MHz. These measurements extend previous Brillouin line-width measurements at higher frequencies into the region where relaxation effects are dominant and connect the optical measurements with lower-frequency acoustical data.
Three detectors sense He-Ne laser beam; one senses reference phase while others, at right angles to first, sense phase offset for each axis. Analog output of axis detectors is multiplied separately by reference output to give X and Y error signals that are then fed to respective X and Y actuators.
The present paper describes an automated system for measuring stellar proper motions on the basis of information contained in photographic plates. In this system, the images on a star plate are digitized by a scanning microdensitometer using light from a He-Ne gas laser, and a special-purpose computer arranges the measurements in computer-compatible form on magnetic tape. The scanning and image-reconstruction processes are briefly outlined, and the image-evaluation techniques are discussed. It is shown that the present system has been especially successful in measuring the proper motions of low-luminosity stars, including 119 stars with less than 1/10,000 of the solar bolometric luminosity. Plans for measurements of high-density Milky Way star plates are noted.
Holographic NDT was used to measure small surface displacements controlled by electric heating by detecting the difference of the interference fringe patterns as viewed through the hologram on a real time basis. A perforated aluminum test plate, with the holes used to position thin metal foils, was used in the experiment. One of the foils was connected to an electric power source and small displacements of the foil were caused and controlled by Ohmic heating. An He-Ne laser was used to perform the holography.
A demonstration of CW parametric upconversion of 3.39-micron IR radiation inside a He-Ne laser's optical cavity is reported. The upconversion was achieved with the aid of a 5145-A argon laser pump and a lithium niobate crystal; the circulating power available inside the pump laser's cavity was used to maximize the efficiency of the upconversion process. Losses associated with the pump blocking filters and with the lithium niobate crystal are discussed. It is concluded that despite the high losses (approximately 12%) associated with the lithium niobate, the highest measured power conversion efficiency of 0.0038 compares favorably with the best CW external conversion efficiency reported to date.
The use of computer generated, reflection holograms in conjunction with high power lasers for precision machining of metals and ceramics was investigated. The Reflection holograms which were developed and made to work at both optical wavelength (He-Ne, 6328 A) and infrared (CO2, 10.6) meet the primary practical requirement of ruggedness and are relatively economical and simple to fabricate. The technology is sufficiently advanced now so that reflection holography could indeed be used as a practical manufacturing device in certain applications requiring low power densities. However, the present holograms are energy inefficient and much of the laser power is lost in the zero order spot and higher diffraction orders. Improvements of laser machining over conventional methods are discussed and addition applications are listed. Possible uses in the electronics industry include drilling holes in printed circuit boards making soldered connections, and resistor trimming.
A single axis rotation sensor, utilizing a 200 m single mode optical fiber in a 30 cm diameter coil has been constructed and tested in the laboratory. A He-Ne laser is the light source for the Sagnac interferometer-mode sensor. The outputs of Si detectors viewing two complementary interference patterns are electronically differenced to obtain a rotation-dependent signal. Linear response over a rotation rate range of about 0.0001 to 0.1 rad/sec was obtained.
The results of a study on the CW nuclear pumped lasing of the He-Ne system are presented. Preliminary experiments measured single pass gain for the 6328.2A laser transition at neutron fluxes up to 1 x 10 to the 14th power neutrons/sq cm sec. Peak gain for a 300 torr (He-3)-Ne (5:1 mixture) was found to be 8.84 dB/meter at a 2 x 10 to the 12th power neutrons/sq cm sec neutron flux. Further experiments measured the gain in the flux region from one million to 2 x 10 to the 12th power neutrons/sq cm sec. In addition, gain vs. probe laser intensity at various neutron fluxes was measured. These measurements resulted in the construction of a laser cavity and the subsequent CW nuclear pumped lasing at 6328.2A in (He-3)-Ne. Experiments were also carried out on the 3.39 micrometer superradiant line in (He-3)-Ne. On three separate occasions, at two different facilities, lasing was observed. Although (He-3)-Ne was found to have the lowest threshold for lasing found so far, it also had the lowest output power on the order of tens of microwatts.
A coaxial dual-channel laser system has been developed for the measurement of extinction coefficients of highly absorbing liquids. An empty wedge-shaped sample cell is first translated laterally through a He-Ne laser beam to measure the differential thickness using interference fringes in reflection. The wedge cell is carefully filled with the oil sample and translated through the coaxially positioned dye laser beam for the differential attenuation or extinction measurement. Optional use of the instrumentation as a single-channel extinction measurement system and also as a refractometer is detailed. The system and calibration techniques were applied to the measurement of two crude oils whose extinction values were required to complete the analysis of airborne laser data gathered over four controlled spills.
In order to relate the measured fringe shift of an interferometer to the density of a medium, the relation between density and refractive index, which is expressed by the specific refractivity, must be known. In the present paper, the specific refractivities of the wind tunnel test gases CF4 and C2F6 are determined in order to verify estimations based on the atomic refractivities of carbon and fluorine. A Twyman-Green two-beam interferometer with a 633-nm He-Ne laser light source was used to measure the specific refractivity as a function of fringe shift as the density of the gas was changed. Values of 0.122 and 0.131 cu cm/g were obtained for CF4 and C2F6 respectively at a temperature of 300 K, which are within 1% of the values computed from the atomic refractivities.
A novel pulsed dual-beam thermal lens technique for the determination of thermal diffusivity of liquids and solids was developed. In this technique a transient thermal lens is formed in the test specimen by using a dye laser pulse as a heating source and the thermal lens decay is monitored by means of a CW He-Ne laser. The technique is fast and contactless and avoids some of the major difficulties of conventional methods. Thermal diffusivities for water and a polycarbonate plastic were measured and found to be in agreement with literature values. Considerable simplification and minimization of certain errors was achieved by use of a reference material.
A laboratory model of a 16 channel integrated optical data preprocessor was fabricated and tested in response to a need for a device to evaluate the outputs of a set of remote sensors. It does this by accepting the outputs of these sensors, in parallel, as the components of a multidimensional vector descriptive of the data and comparing this vector to one or more reference vectors which are used to classify the data set. The comparison is performed by taking the difference between the signal and reference vectors. The preprocessor is wholly integrated upon the surface of a LiNbO3 single crystal with the exceptions of the source and the detector. He-Ne laser light is coupled in and out of the waveguide by prism couplers. The integrated optical circuit consists of a titanium infused waveguide pattern, electrode structures and grating beam splitters. The waveguide and electrode patterns, by virtue of their complexity, make the vector subtraction device the most complex integrated optical structure fabricated to date.
The SL-3 flight on the Space Shuttle will carry a 25 mW He-Ne laser holographic recorder for recording the solution growth of triglycine sulfate (TGS) crystals under low-zero gravity conditions. Three hundred holograms (two orthogonal views) will be taken (on SO-253 film) of each growth experiment. Processing and analysis (i.e., reconstructed imagery, holographic schlieren, reverse reference beam microscopy, and stored beam interferometry) of the holographic records will be done at NASA/MSFC. Other uses of the recorder on the Shuttle have been proposed.
In connection with several experiments proposed for flight on the Space Shuttle, which involve the use of gas lasers, the behavior of a He-Ne laser in a low-gravity environment has been studied theoretically and experimentally in a series of flight tests using a low-gravity-simulation aircraft. No fluctuation in laser output above the noise level of the meter (1 part in 1000 for 1 hr) was observed during the low-gravity portion of the flight tests. The laser output gradually increased by 1.4% during a 1.5-hr test; at no time were rapid variations observed in the laser output. A maximum laser instability of 1 part in 100 was observed during forty low-gravity parabolic maneuvers. The beam remained Gaussian throughout the tests and no lobe patterns were observed.
A 25 mW He-Ne laser holographic recorder for recording the solution growth of triglycine sulfate crystals under low-zero gravity conditions is described. A systems engineering and design analysis, and mechanical and electrical design analyses of the equipmentation are presented. The equipment, fabricated for the Sl-3 flight on the space shuttle, was designed to take 300 holograms (two orthogonal views) on 50-235 film of each growth experiment. Specifications and capabilities for support module mechanical assemblies are lso presented.
Existing techniques were surveyed, an experimental procedure was developed, a laboratory test model was fabricated, limited data were recovered for proof of principle, and the relationship between particle size distribution and amplitude measurements was illustrated in an effort to develop a low cost, simplified optical technique for measuring particle size distributions and velocities in fluidized bed combustors and gasifiers. A He-Ne laser illuminated Rochi Rulings (range 10 to 500 lines per inch). Various samples of known particle size distributions were passed through the fringe pattern produced by the rulings. A photomultiplier tube converted light from the fringe volume to an electrical signal which was recorded using an oscilloscope and camera. The signal amplitudes were correlated against the known particle size distributions. The correlation holds true for various samples.
An instrument has been designed for the measurement of stratospheric trace species which utilizes tunable infrared diode lasers as sources for sensitive in situ absorption spectroscopy in selected wavelength regions. This instrument, the Balloon-Borne Laser In Situ Sensor (BLISS), is a high-resolution absorption spectrometer designed to provide measurements of the concentrations of stratospheric species and their diurnal variations. The instrument employs second-harmonic detection of the absorption of tunable diode laser (TDL) radiation (3-30 microns) in a 1 km path length defined by a retroreflector lowered 0.5 km below the BLISS gondola. Retroreflector tracking under microprocessor control is obtained using a He-Ne laser and coaligned TV camera with CID imaging. Simultaneous measurements of molecular species in the 20-40 km altitude range will be performed using four TDLs, with the predicted minimum-detectable mixing ratio at 30 km being typically less than or equal to 0.1 ppbv.