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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 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

An autoranging scanning system and compatible methods of noise reduction

The autoranging scanning system discussed combines in a unique way four different methods for removing noise. The system employs a narrow-band amplifier. Other noise reduction methods make use of digital summation, convolution numbers, and the coaddition of scans. The system was designed to digitize the output of an infrared spectrometer and to record it on magnetic tape. Light passes through a mechanical light chopper and the spectrometer optics, and falls on the PbS cell to produce a signal which is amplified by the first preamplifier.

Saufley, D. C.↗
DOE OSTI2023

Band Edge Excitons and Amplified Spontaneous Emission of Mercury Chalcogenide Nanoplatelets

Colloidal nanoplatelets of HgSe and HgTe prepared indirectly through cation exchange reactions can transfer many of the advantageous properties of atomically precise, 2D cadmium chalcogenides to the near-infrared (NIR) spectral window. In this work, HgSe and HgTe nanoplatelets are studied to understand their fundamental photophysical properties, particularly those areas of similarity and difference from cadmium-based NPLs, and to examine their potential as optical gain media. Similar to cadmium chalcogenide NPLs, low-temperature photoluminescence of HgTe NPLs displays two-color emission that depends on temperature, sample, fluence, excitation frequency, and irradiation time. Both HgTe and HgSe show nanosecond emission dynamics at temperatures as low as 2.5 K, with no indication that bright-dark excitonic splitting governs the low-temperature photoluminescence. Collectively, experimental data is most consistent with emission from a negative trion state at low temperature. Although the mercury chalcogenide nanoplatelets are shown to have broadened optical resonances compared to the cadmium chalcogenides from which they are derived, they retain slow Auger recombination and can display low-threshold amplified spontaneous emission in the NIR spectral window. Optical pumping thresholds for HgTe NPLs are observed as low as 4.4 µJ cm -2 and highlight the potential 2D nanoplatelets as gain medium in the near-infrared.

36 MATERIALS SCIENCE↗
NASA NTRS2015

Recent Efforts in Advanced High Frequency Communications at the Glenn Research Center in Support of NASA Mission

This presentation will discuss research and technology development work at the NASA Glenn Research Center in advanced frequency communications in support of NASAs mission. An overview of the work conducted in-house and also in collaboration with academia, industry, and other government agencies (OGA) in areas such as antenna technology, power amplifiers, radio frequency (RF) wave propagation through Earths atmosphere, ultra-sensitive receivers, among others, will be presented. In addition, the role of these and other related RF technologies in enabling the NASA next generation space communications architecture will be also discussed.

Optical communications↗
DOE OSTI2025

Versatile & Intelligent Biodetection via Environmental Sensing (VIBES)

Reactive health monitoring strategies during events like the COVID-19 pandemic highlighted the need for predictive, threat-agnostic diagnostics that can detect both known diseases and novel chemical or biological threats. To address this, we investigated an optical biosensor as a breath volatile organic compound (VOC) analyzer, aiming to emulate biological olfaction. We assembled and validated the device with thin film metal coated substrate-based sensors. We immobilized small biological recognition elements on the substrates and delivered controlled concentrations of target VOCs. The sensor was irradiated with a visible laser and the sensor signal was recorded. We characterized the laser performance and tested 3 recognition elements for 2 VOCs with varying concentrations (1-100 ppm). We also evaluated enhancement of the signal using nanostructures on the metal film in comparison with planar film substrate. We demonstrated detecting ethanol reliably at concentrations as low as ~2 ppm along with preliminary detection of acetone (<100 ppm). We also found several unexpected factors that influence the sensor behavior that should be addressed to further refine the device’s performance. The nanostructures were, as expected, found to amplify the sensor signals. These findings demonstrate the feasibility of the optical bio-sensing modality for breath VOC monitoring at physiologically relevant levels. This positions LLNL to develop a low-cost, scalable, broad-spectrum health monitoring capability aligned with the Early Detection thrust of the Bioresilience Mission Focus Area and attract external funding.

47 OTHER INSTRUMENTATION↗
NASA NTRS2001

Power enhanced frequency conversion system

A frequency conversion system includes at least one source providing a first near-IR wavelength output including a gain medium for providing high power amplification, such as double clad fiber amplifier, a double clad fiber laser or a semiconductor tapered amplifier to enhance the power output level of the near-IR wavelength output. The NFM device may be a difference frequency mixing (DFM) device or an optical parametric oscillation (OPO) device. Pump powers are gain enhanced by the addition of a rare earth amplifier or oscillator, or a Ra-man/Brillouin amplifier or oscillator between the high power source and the NFM device.

Sanders, Steven↗
DOE OSTI2023

CHEETAH: Compact High Efficiency Electrically Tunable Amplifier (Final Report)

The goal of this project was to develop a new type of optically triggered, high speed and high power switch for radiofrequency applications with potential to exceed current state-of-the-art power and bandwidth. This device operates under a new operation principle, where discrete packets of charge carriers are generated with defined size. These are then swept out of the device at high enough fields to prevent diffusion and expansion of these packets. Individual pulse widths are determined by the spatial extent of these packets and their drift velocity, which would enable control over both amplitude and frequency by control of the initial packet size, illumination intensity, and applied voltage. This effort demonstrated this new mode of operation, while uncovering a new regime of pulse compression using negative differential mobility (NDM) semiconductors such as GaAs, where the output electrical pulse is substantially shorter than the input optical pulse.

42 ENGINEERING↗
NASA NTRS2013

A Hybrid Fiber/Solid-State Regenerative Amplifier with Tunable Pulse Widths for Satellite Laser Ranging

A fiber/solid-state hybrid seeded regenerative amplifier, capable of achieving high output energy with tunable pulse widths, has been developed for satellite laser ranging applications. The regenerative amplifier cavity uses a pair of Nd:YAG zigzag slabs oriented orthogonally to one another in order to make thermal lensing effects symmetrical and simplify optical correction schemes. The seed laser used is a fiber-coupled 1,064-nm narrowband (<0.02 nm) diode laser that is discretely driven in a new short-pulsed mode, enabling continuously tunable seed pulse widths in the 0.2-to-0.4-ns range. The amplifier gain unit consists of a pair of Brewster-cut 6-bounce zigzag Nd:YAG laser slabs, oriented 90deg relative to each other in the amplifier head. This arrangement creates a net-symmetrical thermal lens effect (an opposing singleaxis effect in each slab), and makes thermo-optical corrections simple by optimizing the curvature of the nearest cavity mirror. Each slab is pumped by a single 120-W, pulsed 808-nm laser diode array. In this configuration, the average pump beam distribution in the slabs had a 1-D Gaussian shape, which matches the estimated cavity mode size. A half-wave plate between the slabs reduces losses from Fresnel reflections due to the orthogonal slabs Brewster-cut end faces. Successful "temporal" seeding of the regenerative amplifier cavity results in a cavity Q-switch pulse envelope segmenting into shorter pulses, each having the width of the input seed, and having a uniform temporal separation corresponding to the cavity round-trip time of approx. =10 ns. The pulse energy is allowed to build on successive passes in the regenerative amplifier cavity until a maximum is reached, (when cavity gains and losses are equal), after which the pulse is electro- optically switched out on the next round trip The overall gain of the amplifier is approx. =82 dB (or a factor of 1.26 million). After directing the amplified output through a LBO frequency doubling crystal, approx. = 2.1 W of 532-nm output (>1 mJ) was measured. This corresponds to a nonlinear conversion efficiency of >60%. Furthermore, by pulse pumping this system, a single pulse per laser shot can be created for the SLR (satellite laser ranging) measurement, and this can be ejected into the instrument. This is operated at the precise frequency needed by the measurement, as opposed to commercial short-pulsed, mode-locked systems that need to operate in a continuous fashion, or CW (continuous wave), and create pulses at many MHz. Therefore, this design does not need to throw away or dump 99% of the laser energy to produce what is required; this system can be far smaller, more efficient, cheaper, and readily deployed in the field when packaged efficiently. Finally, by producing custom diode seed pulses electronically, two major advantages over commercial systems are realized: First, this pulse shape is customizable and not affected by the cavity length or gain of the amplifier cavity, and second, it can produce adjustable (selectable) pulse widths by simply adding multiple seed diodes and coupling each into commercial, low-cost fiber-optic combiners.

Coyle, Barry↗
DOE OSTI2021

Graphene Electric Field Sensor Enables Single Shot Label-Free Imaging of Bioelectric Potentials

The measurement of electrical activity across systems of excitable cells underlies current progress in neuroscience, cardiac pharmacology, and neurotechnology. However, bioelectricity spans orders of magnitude in intensity, space, and time, posing substantial technological challenges. The development of methods permitting network-scale recordings with high spatial resolution remains key to studies of electrogenic cells, emergent networks, and bioelectric computation. Here, for this work, we demonstrate single-shot and label-free imaging of extracellular potentials with high resolution across a wide field-of-view. The critically coupled waveguide-amplified graphene electric field (CAGE) sensor leverages the field-sensitive optical transitions in graphene to convert electric potentials into the optical regime. As a proof-of-concept, we use the CAGE sensor to detect native electrical activity from cardiac action potentials with tens-of-microns resolution, simultaneously map the propagation of these potentials at tissue-scale, and monitor their modification by pharmacological agents. This platform is robust, scalable, and compatible with existing microscopy techniques for multimodal correlative imaging.

47 OTHER INSTRUMENTATION↗
NASA NTRS1972

A superconducting time-variant filtering system.

Description of a laboratory test facility for studying the tracking capabilities of a superconducting time-varying filter system. An RF signal from an antenna is amplified and fed to a mixer; the IF signal modulates an optical diode, and the emitted light is directed through an optical system onto a high-purity high-resistance semiconductor terminating a quarter-wavelength stub in a lead-plated superconducting cavity. The resulting perturbation in the cavity resonant frequency is proportional to the signal modulation present in the light beam. The narrow-band superconducting cavity is thereby acting as a time-variant filter that tracks the instantaneous signal modulation. SNR improvement on the order of 25 dB can be obtained due to the noise rejection characteristics of such a modulation tracking filter.

Arndt, G. D.↗
NASA NTRS1979

Airborne laser induced fluorescence system for measuring OH and other trace gases in the parts-per-quadrillion to parts-per-trillion range

Described in detail is a laser induced fluorescence system which has been successfully interfaced with two aircraft sampling platforms (i.e., Sabreliner jet and an L-188C Electra). This system, which has been under development for four years, presently consists of the following major components: (1) a Nd-Yag laser driven oscillator-amplifier dye laser; (2) a sampling manifold with associated fluorescence detection optics; (3) an OH calibration chamber; (4) a laser beam steering assembly; and (5) sampling electronics and data processing hardware. During the last three years, this system has been flown some 50,000 air miles making tropospheric OH radical measurements over the latitude range of 70 N to 57 S. OH concentrations measured during these flights have ranged from 30 parts-per-quadrillion (3.7 x 10 to the 5th molecules/sq cm) at altitudes of 6 km to 0.8 parts-per-trillion (2.0 x 10 to the 7th molecules/sq cm) at 0.5 km. Computations have been completed which indicate that the existing aircraft system with modest modifications should also be capable of detecting natural tropospheric levels of NO, SO2, CH2O, NO2, HNO2, NO3, H2O2 and CS2 by using both conventional laser-induced fluorescence methodology and multiphoton techniques.

Davis, D. D.↗
DOE OSTI2023

CHEETAH: Compact High Efficiency Electrically Tunable Amplifier (Abbreviated Final Report)

The goal of this project was to develop a new type of optically triggered, high speed and high power switch for radiofrequency applications with potential to exceed current state-of-the-art power and bandwidth. This device operates under a new operation principle, where discrete packets of charge carriers are generated with defined size. These are then swept out of the device at high enough fields to prevent diffusion and expansion of these packets. Individual pulse width are determined by the spatial extent of these packets and their drift velocity, which would enable control over both amplitude and frequency by control of the initial packet size, illumination intensity, and applied voltage. This effort demonstrated this new mode of operation, while uncovering a new regime of pulse compression using negative differential mobility (NDM) semiconductors such as GaAs, where the output electrical pulse is substantially shorter than the input optical pulse.

42 ENGINEERING↗
NASA NTRS2015

Space Optical Communications Using Laser Beam Amplification

The Space Optical Communications Using Laser Beam Amplification (SOCLBA) project will provide a capability to amplify a laser beam that is received in a modulating retro-reflector (MRR) located in a satellite in low Earth orbit. It will also improve the pointing procedure between Earth and spacecraft terminals. The technology uses laser arrays to strengthen the reflected laser beam from the spacecraft. The results of first year's work (2014) show amplification factors of 60 times the power of the signal beam. MMRs are mirrors that reflect light beams back to the source. In space optical communications, a high-powered laser interrogator beam is directed from the ground to a satellite. Within the satellite, the beam is redirected back to ground using the MMR. In the MMR, the beam passes through modulators, which encode a data signal onto the returning beam. MMRs can be used in small spacecraft for optical communications. The SOCLBA project is significant to NASA and small spacecraft due to its application to CubeSats for optical data transmission to ground stations, as well as possible application to spacecraft for optical data transmission.

Laser↗
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 NTRS2009

Free-Space Optical Interconnect Employing VCSEL Diodes

Sensor signal processing is widely used on aircraft and spacecraft. The scheme employs multiple input/output nodes for data acquisition and CPU (central processing unit) nodes for data processing. To connect 110 nodes and CPU nodes, scalable interconnections such as backplanes are desired because the number of nodes depends on requirements of each mission. An optical backplane consisting of vertical-cavity surface-emitting lasers (VCSELs), VCSEL drivers, photodetectors, and transimpedance amplifiers is the preferred approach since it can handle several hundred megabits per second data throughput.The next generation of satellite-borne systems will require transceivers and processors that can handle several Gb/s of data. Optical interconnects have been praised for both their speed and functionality with hopes that light can relieve the electrical bottleneck predicted for the near future. Optoelectronic interconnects provide a factor of ten improvement over electrical interconnects.

Simons, Rainee N.↗
DOE OSTI2023

Final amplifier of an ultra-intense all-OPCPA system with 13-J output signal energy and 41% pump-to-signal conversion efficiency

Optical parametric chirped-pulse amplification (OPCPA) using high-energy Nd:glass lasers has the potential to produce ultra-intense pulses (>10 23 W/cm 2 ). We report on the performance of the final high-efficiency amplifier in an OPCPA system based on large-aperture (63 × 63-mm 2 ) partially deuterated potassium dihydrogen phosphate (DKDP) crystals. The seed beam (180-nm bandwidth, 110 mJ) was provided by the preceding OPCPA stages. A maximum pump-to-signal conversion efficiency of 41% and signal energy up to 13 J were achieved with a 52-mm-long DKDP crystal due to the flattop super-Gaussian pump beam profile and flat-in-time pulse shape.

47 OTHER INSTRUMENTATION↗
DOE OSTI2025

High-speed fiber-coupled terahertz time-domain spectroscopy system using a bias-free plasmonic source

We demonstrate a high-speed fiber-coupled terahertz time-domain spectroscopy (THz-TDS) system using a bias-free plasmonic terahertz source. The system is powered by a compact, low-power femtosecond fiber laser oscillator that drives a dual-branch fiber amplifier to pump and probe a plasmonic terahertz source and detector, respectively. A polarization-maintaining, fiber-coupled optical delay line is employed to precisely control the temporal offset between the pump and probe beams through a compact, robust platform. Operating in the self-similar amplification regime, the fiber amplifiers are engineered to mitigate nonlinear pulse distortion and dispersion while delivering robust, high-energy pulses at a 1560-nm wavelength, with an output power exceeding 326 mW. In reflection mode, the THz-TDS system achieves a peak dynamic range of 81 dB and a bandwidth greater than 3.5 THz at a scan rate of 3.75 Hz. The utility of the system for rapid sensing is further demonstrated by quantifying the porosity and density of pharmaceutical tablets through measurements of their physical thickness and effective refractive index.

Jiang, Xinghe [University of California, Los Angel↗
DOE OSTI2020

Technology of thin-rod Yb : YAG amplifiers with a high pulse energy and average power

Technology for producing thin-rod Yb : YAG laser amplifiers is improved, which is aimed at increasing the output pulse energy and includes the development of a new method for mounting active elements into a cooling system and employment of more persistent dielectric coatings of rod ends. An influence of a thermal lens on the beam size in an active element is theoretically studied and the parameters are found, which provide equal beam sizes at input and output rod ends. The output pulse energy of 4 mJ is obtained without optical breakdown of the output end, which substantially exceeds the previously obtained results. The amplifier demonstrates an average power of 60 W and maintains a high beam quality. (paper)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗