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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS2019

Failure of Nd:YVO4 Amplifier Crystals

Brittle single crystals are used in NASA applications ranging from lenses to centrally heated laser slabs. Despite standard procedures to design such components, unexpected failures occasionally occur. The ICEsat-2 (Ices, cloud, and elevation satellite) employs Yttrium orthovanadate single crystals in laser amplifiers and oscillators. Although the systems are currently flying and successfully operating, some unexpected crystal fractures occurred just prior to flight. The failures were traced to poor crystal quality along with time depend chemical reaction within the system assembly that increased stress beyond expectations and promoted both fast fracture and stress corrosion. This presentation will discuss failure analysis of the crystals and the chemical reactions that promoted failures, along with corrective actions taken to reduce likelihood of fracture over the three year mission. Re-designed lasers were stored for 12 months and operated for a total of 1,000 hours without signs of degradation.

Salem, Jon↗
NASA NTRS2019

Failure of Nd:YVO4 Amplifier Crystals

Brittle single crystals are used in NASA applications ranging from lenses to centrally heated laser slabs. Despite standard procedures to design such components, unexpected failures occasionally occur. The ICEsat-2 (Ices,Cloud, and Elevation satellite-2) employs Yttrium orthovanadate single crystals in laser amplifiers and oscillators. Although the systems are currently flying and successfully operating, some unexpected crystal fractures occurred just prior to flight. The failures were traced to poor crystal quality along with time-dependent chemical reaction within the system assembly that increased stress beyond expectations and promoted both fast fracture and stress corrosion. This presentation will discuss failure analysis of the crystals and the chemical reactions that promoted failures, along with corrective actions taken to reduce likelihood of fracture over the three-year mission. Re-designed lasers were stored for 12 months and operated for a total of 1,000 hours without signs of degradation.

Design↗
NASA NTRSDate not supplied

Initial Results from NASA’s Low-Cost Optical Terminal (LCOT) at Goddard Space Flight Center

We present the initial results from testing of the Low-Cost Optical Terminal (LCOT) at NASA-Goddard Space Flight Center (GSFC). LCOT is designed to be a single modular design that can be quickly reconfigured to support different laser communication missions. LCOT is built around a 70 cm commercially available telescope designed with optical and quantum communications in mind. We have installed a state-of-the-art adaptive optics system, novel high-power laser amplifiers, and other innovative subsystems developed by our team to facilitate laser communications. We have conducted tests of our LCOT system against operational space terminals, demonstrating our ability to receive a downlink and transmit an uplink. We show the results of these tests and give analysis of the results.

Laser communications↗
NASA NTRSDate not supplied

Initial Results from NASA’s Low-Cost Optical Terminal (LCOT) at Goddard Space Flight Center

We present the initial results from testing of the Low-Cost Optical Terminal (LCOT) at NASA-Goddard Space Flight Center (GSFC). LCOT is designed to be a single modular design that can be quickly reconfigured to support different laser communication missions. LCOT is built around a 70 cm commercially available telescope designed with optical and quantum communications in mind. We have installed a state-of-the-art adaptive optics system, novel high-power laser amplifiers, and other innovative subsystems developed by our team to facilitate laser communications. We have conducted tests of our LCOT system against operational space terminals, demonstrating our ability to receive a downlink and transmit an uplink. We show the results of these tests and give an analysis of the results.

Ground terminals↗
NASA NTRS1992

High power master oscillator power amplifier (MOPA) AlGaAs laser for intersatellite communications

A master oscillator power amplifier (MOPA) configuration has been developed using an anti-reflection-coated AlGaAs semiconductor broad area laser in a reflective amplifier mode. For CW injection, the MOPA produced 340 mW of diffraction-limited power. The semiconductor MOPA configuration also produced peak diffraction-limited powers of 360 mW and 320 mW for quaternary pulse position Q-PPM modulation rates of 50 Mbps and 325 Mbps, respectively, for a peak injected power of 100 mW. Angular beamsteering during modulation was minimized by collimating the injected beam. The diffraction-limited peak power was limited by the frequency chirp of the master oscillator and also by the coupling losses of the injected beam.

Cornwell, Donald M., Jr.↗
NASA NTRS1985

Laboratory measurement of the S(9) pure rotation frequency in H2

The S(9) J = 11-9 ground-state transition in H2 is investigated experimentally, applying a 514.5-nm 300-mW single-mode CW Ar-ion laser to probe the stimulated Raman emission of a CH4-air flame pumped by a single-frequency electronically scannable dye laser amplified to 2 MW by a 10-Hz frequency-doubled Nd:YAG laser. An H2 Raman spectrum with an S(9) frequency of 2130.102 + or - 0.004/cm is shown, and the results are found to be consistent with the measurements obtained in the Orion molecular cloud by Knacke and Young (1980 and 1981).

Jennings, D. E.↗
NASA NTRS2012

Airborne Measurements of Atmospheric Pressure made Using an IPDA Lidar Operating in the Oxygen A-Band

We report airborne measurements of atmospheric pressure made using an integrated path differential absorption (IPDA) lidar that operates in the oxygen A-band near 765 nm. Remote measurements of atmospheric temperature and pressure are needed for NASA s Active Sensing of CO2 Emissions Over Nights, Days, and Seasons (ASCENDS) mission to measure atmospheric CO2. Accurate measurements of tropospheric CO2 on a global scale are very important in order to better understand its sources and sinks and to improve our predictions of climate change. The goal of ASCENDS is to determine the CO2 dry mixing ratio with lidar measurements from space at a level of ~1 ppm. Analysis to date shows that with current weather models, measurements of both the CO2 column density and the column density of dry air are needed. Since O2 is a stable molecule that uniformly mixed in the atmosphere, measuring O2 absorption in the atmosphere can be used to infer the dry air density. We have developed an airborne (IPDA) lidar for Oxygen, with support from the NASA ESTO IIP program. Our lidar uses DFB-based seed laser diodes, a pulsed modulator, a fiber laser amplifier, and a non-linear crystal to generate wavelength tunable 765 nm laser pulses with a few uJ/pulse energy. The laser pulse rate is 10 KHz, and average transmitted laser power is ~20 mW. Our lidar steps laser pulses across a selected line O2 doublet near 764.7 nm in the Oxygen A-band. The direct detection lidar receiver uses a 20 cm diameter telescope, a Si APD detector in Geiger mode, and a multi-channel scalar to detect and record the time resolved laser backscatter in 40 separate wavelength channels. Subsequent analysis is used to estimate the transmission line shape of the doublet for the laser pulses reflected from the ground. Ground based data analysis allows averaging from 1 to 60 seconds to increase SNR in the transmission line shape of the doublet. Our retrieval algorithm fits the expected O2 lineshapes against the measurements and determines the atmospheric pressure by minimizing the error between the observations and model. We first demonstrated our airborne lidar during flights during summer 2010. We made several improvements and made measurements during the Ascends flights during July 2011. More information about the technique, lidar instrument, airborne measurements, and pressure estimates will be described in the presentation.

Riris, Haris↗
NASA NTRS1982

The effect of space charge fields due to finite length electron beams in the free-electron laser

The space charge electric field of a finite length electron beam in the free electron laser amplifier with a tapered wiggler is analyzed. In the free drift region between the accelerator and laser, expressions for the increase of energy spread due to the self field are presented. In the FEL interaction region, the general conditions on the importance of the self electric field in the equations of motion is obtained. A numerical example of the FEL experiment at 10.6 microns is given.

Tang, C.-M.↗
NASA NTRSDate not supplied

Current Status of NASA’s Low-Cost Optical Terminal (LCOT) at Goddard Space Flight Center

This paper provides the status of ongoing work at NASA-Goddard Space Flight Center (GSFC) to build a low-cost flexible ground terminal for optical communication. For laser communication to be cost-effective for future missions, a global network of flexible optical terminals must be put in place. There is a need for a single ground terminal design capable of supporting multiple missions ranging from LEO to lunar distances. NASA’s Low-Cost Optical Terminal (LCOT) has a single modular design that can be quickly reconfigured to support different laser communications missions. The LCOT prototype uses a 70cm commercially available telescope designed with optical and quantum communications in mind. This telescope is currently being integrated with a state-of-the-art adaptive optics system, and novel high-power laser amplifier demonstrate its utility as an optical communications receiver by receiving a downlink from the recently launched Laser Communication Relay Demonstration (LCRD). LCOT uses commercially available components wherever possible, and where commercial options are not available, the LCOT team works with vendors to create commercial options. This paper discusses the development progress for the blueprint of NASA’s future global ground terminal network.

Laser communications↗
NASA NTRS1981

Advanced solar energy conversion

An atomic iodine laser, a candidate for the direct solar pumped lasers, was successfully excited with a 4 kW beam from a xenon arc solar simulator, thus proving the feasibility of the concept. The experimental set up and the laser output as functions of operating conditions are presented. The preliminary results of the iodine laser amplifier pumped with the HCP array to which a Q switch for giant pulse production was coupled are included. Two invention disclosures - a laser driven magnetohydrodynamic generator for conversion of laser energy to electricity and solar pumped gas lasers - are also included.

Lee, J. H.↗
NASA NTRS1978

Laser amplification of incoherent radiation

The amplification of noise in a laser amplifier is treated theoretically. The model for the active medium and its description using density-matrix techniques, are taken from the theory of laser operation. The spectral behavior of the radiation in the nonlinear regime is studied and the formalism is written from the onset in the frequency domain. The statistics of the light are gradually modified by the nonlinear amplification process, and expressions are derived for the rate of change of fluctuations in intensity as a measure of statistical changes. In addition, the range of validity of Litvak's Gaussian-statistics approximation is discussed. In the homogeneous-broadening case, the evolution of initially broadband Gaussian radiation toward quasimonochromatic oscillations with laserlike statistics is explored in several numerical examples. The connections of this study with the time-domain work on self-pulsing in a ring-laser configuration, are established. Finally, spectral-narrowing and -rebroadening effects in Doppler-broadened media are discussed both analytically and with numerical examples. These examples show the distinct contribution of pulsations in the population ('Raman-type terms'), and saturation phenomena.

Menegozzi, L. N.↗
NASA NTRS1992

An ultra-sensitive coherent detector capable of single photon detection for lidar applications

The properties of Ultra-Sensitive Coherent Detectors (USCD's) are nearly that of an ideal detector for lidar applications. Recent progress in the development of USCD's is briefly reviewed, and its imaging capability is demonstrated. These new detectors possess properties with significant improvements over conventional technology. These improvements include a high quantum efficiency of 0.95, gain in excess of 10 exp 13, a narrow bandwidth of 180-300 MHz at 1 micron, imaging capability, and phase conjugation ability. We have constructed a USCD using two Nd:YAG laser amplifiers and a four-wave Brillouin mirror (FWBM) using SnCl4 as the Brillouin medium. Using a 10 Hz repetitively-pulsed single frequency laser, we have shown that the Brillouin medium is free from thermal blooming and from optical breakdown.

Amimoto, Sherwin↗
NASA NTRS2002

Double-Pulsed 2-micron Laser Transmitter for Multiple Lidar Applications

A high energy double-pulsed Ho:Tm:YLF 2-micron laser amplifier has been demonstrated. 600 mJ per pulse pair under Q-switch operation is achieved with the gain of 4.4. This solid-state laser source can be used as lidar transmitter for multiple lidar applications such as coherent wind and carbon dioxide measurements.

Singh, Upendra N.↗
NASA NTRS2012

NASA Tech Briefs, July 2012

Topics covered include: Instrument Suite for Vertical Characterization of the Ionosphere-Thermosphere System; Terahertz Radiation Heterodyne Detector Using Two-Dimensional Electron Gas in a GaN Heterostructure; Pattern Recognition Algorithm for High-Sensitivity Odorant Detection in Unknown Environments; Determining Performance Acceptability of Electrochemical Oxygen Sensors; Versatile Controller for Infrared Lamp and Heater Arrays; High-Speed Scanning Interferometer Using CMOS Image Sensor and FPGA Based on Multifrequency Phase-Tracking Detection; Ultra-Low-Power MEMS Selective Gas Sensors; Compact Receiver Front Ends for Submillimeter-Wave Applications; Dynamically Reconfigurable Systolic Array Accelerator; Blocking Losses With a Photon Counter; Motion-Capture-Enabled Software for Gestural Control of 3D Mod; Orbit Software Suite; CoNNeCT Baseband Processor Module Boot Code SoftWare (BCSW); Trajectory Software With Upper Atmosphere Model; ALSSAT Version 6.0; Employing a Grinding Technology to Assess the Microbial Density for Encapsulated Organisms; Demonstration of Minimally Machined Honeycomb Silicon Carbide Mirrors; Polyimide Aerogel Thin Films; Nanoengineered Thermal Materials Based on Carbon Nanotube Array Composites; Composite Laminate With Coefficient of Thermal Expansion Matching D263 Glass; Robust Tensioned Kevlar Suspension Design; Focal Plane Alignment Utilizing Optical CMM; Purifying, Separating, and Concentrating Cells From a Sample Low in Biomass; Virtual Ultrasound Guidance for Inexperienced Operators; Beat-to-Beat Blood Pressure Monitor; Non-Contact Conductivity Measurement for Automated Sample Processing Systems; An MSK Radar Waveform; Telescope Alignment From Sparsely Sampled Wavefront Measurements Over Pupil Subapertures; Method to Remove Particulate Matter from Dusty Gases at Low Pressures; Terahertz Quantum Cascade Laser With Efficient Coupling and Beam Profile; Measurement Via Optical Near-Nulling and Subaperture Stitching; 885-nm Pumped Ceramic Nd:YAG Master Oscillator Power Amplifier Laser System; Airborne Hyperspectral Imaging System; Heat Shield Employing Cured Thermal Protection Material Blocks Bonded in a Large-Cell Honeycomb Matrix; and Asymmetric Supercapacitor for Long-Duration Power Storage.

Source record↗
NASA NTRS1988

Synchronously pumped mode-locked Ti:Al2O3 lasers

Synchronously pumped mode-locked laser operation in a Ti:Al2O3 ring laser is demonstrated. The laser pump source was a frequency-doubled Nd:YAG laser-amplifier system producing a 60-micron-long macropulse that comprised a wavetrain of mode-locked 70-ps micropulses with a 10-ns spacing (100 MHz). The Ti:Al2O3 laser consisted of a 1-cm-long crystal with faces cut at the Brewster angle and placed in a ring laser cavity configuration with a 2 percent output coupling mirror. The cavity was adjusted for a 5-ns round trip transit time, which was close to half the temporal spacing of the pump pulse. When the crystal was pumped synchronously at 532 nm with a 30-mJ macropulse, which was approximately an order of magnitude above the laser threshold, mode-locked lasing at approximately 200 MHz was obtained. This macropulse pump energy corresponds to an average micropulse pump energy of about 5 microJ at the Ti:Al2O3 crystal face. The mode-locked operation of the Ti:Al2O3 was observed only after several microseconds into the macropulse, indicating a long build-up process over many cavity trips. During this time, relaxation oscillations were observed. When mode locking started, the relaxation oscillation frequency increased by an order of magnitude. Synchronous pumping has been limited to operation with dye lasers and used either a CW or pulsed mode-locked pump source. Recent work has demonstrated CW mode-locked operation of a Ti:Al2O3 laser. The result raises the possibility that pulsed synchronous pumping may be used to obtain significantly narrowed laser pulses in Ti:Al2O3.

Source record↗
NASA NTRS2012

Technology Development for High Efficiency Optical Communications

Deep space optical communications is a significantly more challenging operational domain than near Earth space optical communications, primarily due to effects resulting from the vastly increased range between transmitter and receiver. The NASA Game Changing Development Program Deep Space Optical Communications Project is developing four key technologies for the implementation of a high efficiency telecommunications system that will enable greater than 10X the data rate of a state-of-the-art deep space RF system (Ka-band) for similar transceiver mass and power burden on the spacecraft. These technologies are a low mass spacecraft disturbance isolation assembly, a flight qualified photon counting detector array, a high efficiency flight laser amplifier and a high efficiency photon counting detector array for the ground-based receiver.

Space Receiver↗