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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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Generation of high-power nanosecond pulses from laser diode-pumped Nd:YAG lasers

Simulation results are used to compare the pulse energy levels and pulse energy widths that can be achieved with LD-pumped Nd:YAG lasers for both the pulse-transmission mode (PTM) and pulse-reflection mode (PRM) Q-switching methods for pulse energy levels up to hundreds of microjoules and pulse widths as short as 1 ns. It is shown that high-power pulses with pulse widths as short as 1 ns can be generated with PTM Q-switched in LD-pumped Nd:YAG lasers. With the PRM Q-switching method, pulse widths as short as 2 ns and pulse energy at the level of a few hundred microjoules can also be achieved but require pumping with 8-10-mJ AlGaAs laser diode arrays.

Chan, Kinpui↗
NASA NTRS1988

Diode-pumped laser research

The Laboratory for Oceans is currently working on the development of compact laser diode array (LD) pumped Nd:YAG lasers for use in space-based altimetry and ranging. Laser diode-array pumping technology promises to increase the electrical to optical efficiency of solid state lasers by an order of magnitude with a lifetime increase of nearly three orders of magnitude relative to today's conventional flashlamp-pumped laser systems. The small size, efficiency, and ruggedness make LD-pumped solid state lasers ideal for space based applications. In an in-house RTOP effort, a novel multiple-pass LD-pumped Nd:YAG laser amplifier was designed and tested to increase the 100 microjoule output pulse energy of the Lightwave laser oscillator. Preliminary results have yielded a round trip amplifier gain of about 15 percent using 7 microjoule LD-pump energy. As a parallel activity, funding was recently obtained to investigate the possible use of custom made fiber optic arrays to obtain an efficient optical coupling mechanism between the emitting laser diode-arrays and the target solid state laser material. Fiber optic coupling arrays would allow for the easy manipulation of the spatial emitting pattern of the diode pump sources to match either an end or side pumping laser configuration.

Ramos-Izquierdo, L.↗
NASA NTRS1988

Free-flying experiment to measure the Schawlow-Townes linewidth limit of a 300 THz laser oscillator

Recent advances in laser diode-pumped solid state laser sources permit the design and testing of laser sources with linewidths that approach the Schawlow-Townes limit of 1 Hz/mW of output power. Laser diode pumped solid state ring oscillators have been operated with CW output power levels of 25 mW at electrical efficiencies that exceed 6 percent. These oscillators are expected to operate for lifetimes that approach those of the laser diode sources which is now approaching 20,000 hours. The efficiency and lifetime of these narrow linewidth laser sources will enable space measurements of gravity waves, remote sensing applications (including local range rate and measurements), and laser sources for frequency and time standards. A free-flight experiment, 'SUNLITE', is being designed to measure the linewidth of this all-solid-state laser system.

Byer, R. L.↗
NASA NTRS1988

Fast frequency tuning and phase locking of diode-pumped Nd:YAG ring lasers

A diode-pumped single-mode monolithic Nd:YAG ring-laser oscillator has been built which can be tuned piezoelectrically over several tens of MHz in a few microsecs. Frequency stability over 1 msec is better than 500 Hz. Two lasers have been electronically phase locked for periods of minutes with a phase noise of 29 mrad rms.

Kane, Thomas J.↗
NASA NTRS1988

Advances in solid state laser technology for space and medical applications

Recent developments in laser technology and their potential for medical applications are discussed. Gas discharge lasers, dye lasers, excimer lasers, Nd:YAG lasers, HF and DF lasers, and other commonly used lasers are briefly addressed. Emerging laser technology is examined, including diode-pumped lasers and other solid state lasers.

Byvik, C. E.↗
NASA NTRS1987

Multiple-pass laser-diode-pumped Nd:YAG amplifier - Design

A method for designing a miniature laser-diode-pumped Nd-YAG laser amplifier based on total internal reflection and a multiple-pass slab geometry is described. This new design leads to a simple and practical configuration which allows multiple-pass amplification to be accomplished fairly easily by utilizing an optical arrangement with external mirrors. It is suggested that this type of miniature Nd-YAG amplifier combined with a laser diode-pumped Nd:YAG oscillator could result in an excellent laser-ranging source laser.

Chan, Kinpui↗
NASA NTRS1987

High energy efficient solid state laser sources

Diode-laser-pumped solid-state laser oscillators and nonlinear processes were investigated. A new generation on nonplanar oscillator was fabricated, and it is anticipated that passive linewidths will be pushed to the kilohertz regime. A number of diode-pumped laser transitions were demonstrated in the rod configuration. Second-harmonic conversion efficiencies as high as 15% are routinely obtained in a servo-locked external resonant doubling crystal at 15 mW cw input power levels at 1064 nm.

Byer, Robert L.↗
NASA NTRS1973

High data rate optical transceiver terminal

The objectives of this study were: (1) to design a 400 Mbps optical transceiver terminal to operate from a high-altitude balloon-borne platform in order to permit the quantitative evaluation of a space-qualifiable optical communications system design, (2) to design an atmospheric propagation experiment to operate in conjunction with the terminal to measure the degrading effects of the atmosphere on the links, and (3) to design typical optical communications experiments for space-borne laboratories in the 1980-1990 time frame. As a result of the study, a transceiver package has been configured for demonstration flights during late 1974. The transceiver contains a 400 Mbps transmitter, a 400 Mbps receiver, and acquisition and tracking receivers. The transmitter is a Nd:YAG, 200 Mhz, mode-locked, CW, diode-pumped laser operating at 1.06 um requiring 50 mW for 6 db margin. It will be designed to implement Pulse Quaternary Modulation (PQM). The 400 Mbps receiver utilizes a Dynamic Crossed-Field Photomultiplier (DCFP) detector. The acquisition receiver is a Quadrant Photomultiplier Tube (QPMT) and receives a 400 Mbps signal chopped at 0.1 Mhz.

Clarke, E. S.↗
NASA NTRS1989

Prototype laser-diode-pumped solid state laser transmitters

Monolithic, diode-pumped Nd:YAG ring lasers can provide diffraction-limited, single-frequency, narrow-linewidth, tunable output which is adequate for use as a local oscillator in a coherent communication system. A laser was built which had a linewidth of about 2 kHz, a power of 5 milliwatts, and which was tunable over a range of 30 MHz in a few microseconds. This laser was phase-locked to a second, similar laser. This demonstrates that the powerful technique of heterodyne detection is possible with a diode-pumped laser used as the local oscillator. Laser diode pumping of monolithic Nd:YAG rings can lead to output powers of hundreds of milliwatts from a single laser. A laser was built with a single-mode output of 310 mW. Several lasers can be chained together to sum their power, while maintaining diffraction-limited, single frequency operation. This technique was demonstrated with two lasers, with a total output of 340 mW, and is expected to be practical for up to about ten lasers. Thus with lasers of 310 mW, output of up to 3 W is possible. The chaining technique, if properly engineered, results in redundancy. The technique of resonant external modulation and doubling is designed to efficiently convert the continuous wave, infrared output of our lasers into low duty-cycle pulsed green output. This technique was verified through both computer modeling and experimentation. Further work would be necessary to develop a deliverable system using this technique.

Kane, Thomas J.↗
NASA NTRS1989

Frequency fluctuations of a diode-pumped Nd:YAG ring laser

The spectral density of the frequency fluctuations of a diode-pumped single-mode monolithic Nd:YAG ring laser was measured by locking a Fabry-Perot resonator to the laser frequency. The fluctuations approach the limit due to spontaneous emission (the Schawlow-Townes limit) at frequencies above 80 kHz. The inherent frequency stability of these lasers makes them attractive as a potential light source for gravitational-wave interferometers.

Fritschel, Peter↗
NASA NTRS1985

Tunable solid state lasers for remote sensing; Proceedings of the Conference, Stanford University, CA, October 1-3, 1984

Papers are presented on solid-state lasers for remote sensing, diode-pumped Nd:YAG lasers, and tunable solid-state-laser systems. Topics discussed include titanium-sapphire tunable laser systems, the performance of slab geometry, and the development of slab lasers. Consideration is given to garnet host solid-state lasers, the growth of lasers and nonlinear materials, and nonlinear frequency conversion and tunable sources.

Byer, R. L.↗
NASA NTRS1985

Nd:YAG end pumped by semiconductor laser arrays for free space optical communications

Preliminary experimental results are reported for a diode-pumped Nd:YAG laser employing a tightly focused end-pump geometry. The resonator configuration is planoconcave, with the pumped end of the Nd:YAG rod being coated for high reflection at 1.06 microns. This geometry rectifies nearly all the inefficiencies plaguing side-pumped schemes. This laser is further considered as a candidate for optical communication over the deep space channel.

Sipes, D. L., Jr.↗
NASA NTRS1986

Diode-pumped continuous-wave Nd:glass laser

The paper reports on diode-laser pumping of monolithic Nd:glass laser oscillators. End pumping with a single-stripe diode laser, a threshold of 2.2 mW, and a slope efficiency of 42 percent were observed on a 2-mm-long oscillator with a mode radius of 35 microns. The oscillator generated 2.5 mW of single-ended output power in many axial modes.

Kozlovsky, W. J.↗
NASA NTRS1988

Modulation techniques for deep-space pulse-position modulation (PPM) optical communication

The extremely energy-efficient pulse-position modulation (PPM) format is being actively developed as a basis for optical communications with deep-space probes. Attention is presently given to different modulation schemes for the efficient production of laser pulses over a broad range of repetition rates. Both Q-switching and cavity dumping modulation methods are available for the envisioned diode-pumped Nd:YAG laser source. Numerical calculation results are presented for cavity-dumping.

Rayman, Marc D.↗
NASA NTRS1988

Diode laser-pumped solid-state lasers

Recently, interest in diode laser-pumped solid-state lasers has increased due to their advantages over flashlamp-pumped solid-state lasers. A historical overview is presented of semiconductor diode-pumped solid-state lasers beginning with work in the early 1960s and continuing through recent work on wavelength extension of these devices by laser operation on new transitions. Modeling of these devices by rate equations to obtain expressions for threshold, slope efficiency, and figures of merit is also given.

Fan, Tso Yee↗
NASA NTRS1988

Lunar observer laser altimeter

Understanding the global topography of the Moon is especially important for answering questions concerning lunar origin and evolution. Many outstanding problems in lunar science can be addressed with high resolution topographic data. The severe power, mass, size, and data-rate limitations imposed by the Lunar Geoscience Observer (LGO) and other Observer-class missions are major challenges for all instruments capable of measuring topography. A radar altimeter that meets these strict requirements could obtain a global prespective of lunar topography with a few kilometers spatial resolution and 10 m vertical resolution from a lunar orbit of 100 km. A prototype model is being constructed of the Lunar Observer Laser Altimeter (LOLA) capable of continuously measuring the range to the lunar surface with sub-meter vertical resolution within a 30 to 300 m diameter surface footprint. This same instrument is also designed to provide a direct measure of the surface height distribution in the footprint by waveform analysis of the backscattered laser pulse. Both these measurements are to be made in a continuous, nadir profile across the lunar surface from a 100 km orbit. The wavelength of the altimeter is 1064 nm. A short-pulse (2 nsec), diode-pumped Nd:YAG laser combined with a 25 cm diameter telescope, silicon avalanche photodiode detector, ranging electronics, and instrument computer was designed to make these measurements and meet all the requirements of the LGO mission.

Bufton, J. L.↗
NASA NTRS1989

Laser altimetry measurements from aircraft and spacecraft

The techniques involved in the design and application of laser altimeter instruments are reviewed, including a description of the instrument subsystems required for the range and waveform measurements. Laser pulse transmitters based on the relatively novel technology of diode-pumped solid-state lasers are considered. Various factors affecting laser altimeter instrument performance are discussed. These include the receiver signal-to-noise ratio, atmospheric propagation, and altimeter platform effects. Some examples of laser altimeter data are presented to illustrate the variety of possible instrument applications.

Bufton, Jack L.↗
NASA NTRS1985

Conducting a wind sensing study

Signal-to-noise requirements, and how signal-to-noise determines wind velocity measurement accuracy were studied. A Nd:YAG-based system was found to be competitive with a CO2-based system. Hardware was developed for a coherent Nd:YAG LIDAR system, and is being integrated into a functioning system. A diode-pumped monolithic rod laser to be used as a reference oscillator, a high-power, single-mode ring laser, for use as a master oscillator, and a high-gain, multipass amplifier were constructed.

Byer, R. L.↗