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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 523 records · Page 29
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Spectroscopic studies and analysis of the laser states of Nd/3+/ in YVO4

Polarized absorption and dye-laser excited fluorescence spectra of Nd/3+/ in the Y(3+) site of yttrium orthovanadate at 85 and 300 K are presented and analyzed. The absence of allowed transitions and the unusual concentration of line strength into one transition in pi polarization within a given line group is shown by the Judd-Ofelt theory to be a consequence of the D2d symmetry of the site and ion placements in the unit cell. An energy level scheme giving level positions, level identities, and observed transitions is presented. The principal laser line in this group at about 10640.9 A was found to be predominately pi polarized and to have a cross section of 30 x 10 to the 19th/sq cm, which is 4.6 times larger than the laser transition of Nd/3+/ in YAG.

Pappas Yaney, P.↗
NASA NTRS1994

Laser optogalvanic wavelength calibration with a commercial hollow cathode iron - neon discharge lamp

351 optogalvanic transitions have been observed in the 337 - 598 nm wavelength region using an iron - neon hollow cathode discharge lamp and a pulsed tunable dye laser. 223 of these have been identified as transitions associated with neon energy levels. These optogalvanic transitions have allowed, in conjunction with interference fringes recorded concomitantly with an etalon, the calibration of the dye laser wavelength with 0.3/cm accuracy.

Zhu, Xinming↗
NASA NTRS1994

Measurement of the V-T Energy Transfer Rates of Highly Excited (sup 2)A(sub 1) NO(sub 2)

Production of electronic ground state NO(sub 2) from 248 nm photolysis of HNO(sub 3) was detected by laser induced fluorescence (LIF). A growth in the LIF signal was observed following the photolysis and has been interpreted as the relaxation of NO(sub 2) through the higher vibrational levels of the X state; an energy region where the probe laser photodissociates the NO(sub 2) instead of inducing fluorescence.

laser induced fluorescence (LIF)↗
DOE OSTI2020

HIV influences clustering and intracellular replication of hepatitis C virus

We report HCV and HIV coinfection is common and HIV leads to increased HCV viraemia and accelerated disease progression. However, the biological basis of this interaction remains poorly understood and little is known about the impact of HIV on HCV replication at the cellular level. We analysed HCV RNA, based on single-cell laser-capture microdissection, in liver biopsies from monoinfected (n = 4) and HCV/HIV-coinfected (n = 5) participants. HCV RNA was assayed in 3200 hepatocytes with information of spatial position. We compared HCV RNA levels and clustering properties of infection between mono- and coinfected participants, and developed a mathematical model of infection. Although the median plasma HCV RNA level and the fraction of infected cells were comparable in monoinfected (7.0 log 10 IU/mL and ~ 30%) and coinfected (7.3 log 10 IU/mL and ~ 40%) participants, the median HCV RNA per infected hepatocyte in monoinfected (2.8IU) was significantly lower than in coinfected (8.2IU) participants (p = .03). Clustering of infected cells was more prominent in monoinfected participants (91% of samples) than in coinfected participants (~48%), p = .0045, suggesting that spatial spread may be influenced by HIV coinfection. Interestingly, when clustering does occur, the size of clusters is similar in both types of infection. A mathematical model of infection suggested that HIV allows higher intracellular accumulation of HCV RNA by impeding the export of HCV RNA. Our observations show that HIV coinfection impacts intracellular accumulation of HCV RNA and the clustering of HCV-infected cells, but to a less extent the fraction of HCV-infected cells.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1992

Two micron laser development for atmospheric remote sensing at NASA Langley Research Center

The topics addressed are: (1) eye safety revision of infrared MPE; (2) Tm:Ho dynamics characterization, which includes spectroscopy, laser experiments, and modeling; and (3) Q.M. model calculation, which includes energy levels, electric and magnetic dipole transition probabilities, lifetimes, branching ratios, absorption spectra, and emission spectra; (3) Q.M. model calculation; and (4) heat propagation in a laser rod.

Brockman, Philip↗
NASA NTRS1994

Computational modelling of Er(3+): Garnet laser materials

The Er(3+) ion has attracted a lot of interest for four reasons: (1) Its (4)I(sub 13/2) yields (4)I(sub 15/2) transition lases in the eyesafe region near 1.5 micron; (2) the (4)I(sub 13/2) transition lases near 2.8 micron, an important wavelength for surgical purposes; (3) it displays surprisingly efficient upconversion with lasing observed at 1.7, 1.2, 0.85, 0.56, 0.55, and 0.47 micron following 1.5 micron pumping; and (4) it has absorption bands at 0.96 and 0.81 micron and thus can be diode pumped. However, properties desirable for upconversion reduce the efficiency of 1.5 and 3 micron laser operation and vice versa. Since all of the processes are influenced by the host via the crystal field induced stark splittings in the Er levels, this project undertook modelling of the host influence on the Er lasinng behavior. While growth and measurement of all ten Er(3+) doped garnets is the surest way of identifying hosts which maximize upconversion (or conversly, 1.5 and 3 micron performance), it is also expensive - costing approximately $10,000/material or approximately $100,000 for the materials computationally investigated here. The calculations were performed using a quantum mechanical point charge model developed by Clyde Morrison at Harry Diamond Laboratories. The programs were used to fit the Er:YAG experimental energy levels so that the crystal field parameters, B(sub nm) could be extracted. From these radial factors, rho (sub n) were determined for Er(3+) in garnets. These, in combination with crystal field components, Anm, available from X-ray data, were used to predict energy levels for Er in the other nine garnet hosts. The levels in Er:YAG were fit with an rms error of 12.2/cm over a 22,000/cm range. Predicted levels for two other garnets for which literature values were available had rms errors of less than 17/cm , showing the calculations to be reliable. Based on resonances between pairs of calculated stark levels, the model predicts GSGG as the best host for 1.5 micron laser operation, GSGG or YSAG as the best host for a 2.8 micron operation, and LuGG as the best host for an upconversion material.

Spangler, Lee H.↗
NASA NTRS1988

Overview and future direction for blackbody solar-pumped lasers

A review of solar-pumped blackbody lasers is given which addresses their present status and suggests future research directions. The blackbody laser concept is one system proposed to scale to multimegawatt power levels for space-to-space power transmissions for such applications as onboard spacecraft electrical or propulsion needs. Among the critical technical issues are the scalability to high powers and the laser wavelength which impacts the transmission optics size as well as the laser-to-electric converter at the receiver. Because present blackbody solar-pumped lasers will have laser wavelengths longer than 4 microns, simple photovoltaic converters cannot be used, and transmission optics will be large. Thus, future blackbody laser systems should emphasize near visible laser wavelengths.

Deyoung, R. J.↗
NASA NTRS2003

Theodolite with CCD Camera for Safe Measurement of Laser-Beam Pointing

The simple addition of a charge-coupled-device (CCD) camera to a theodolite makes it safe to measure the pointing direction of a laser beam. The present state of the art requires this to be a custom addition because theodolites are manufactured without CCD cameras as standard or even optional equipment. A theodolite is an alignment telescope equipped with mechanisms to measure the azimuth and elevation angles to the sub-arcsecond level. When measuring the angular pointing direction of a Class ll laser with a theodolite, one could place a calculated amount of neutral density (ND) filters in front of the theodolite s telescope. One could then safely view and measure the laser s boresight looking through the theodolite s telescope without great risk to one s eyes. This method for a Class ll visible wavelength laser is not acceptable to even consider tempting for a Class IV laser and not applicable for an infrared (IR) laser. If one chooses insufficient attenuation or forgets to use the filters, then looking at the laser beam through the theodolite could cause instant blindness. The CCD camera is already commercially available. It is a small, inexpensive, blackand- white CCD circuit-board-level camera. An interface adaptor was designed and fabricated to mount the camera onto the eyepiece of the specific theodolite s viewing telescope. Other equipment needed for operation of the camera are power supplies, cables, and a black-and-white television monitor. The picture displayed on the monitor is equivalent to what one would see when looking directly through the theodolite. Again, the additional advantage afforded by a cheap black-and-white CCD camera is that it is sensitive to infrared as well as to visible light. Hence, one can use the camera coupled to a theodolite to measure the pointing of an infrared as well as a visible laser.

Crooke, Julie A.↗
NASA NTRS1994

High power diode lasers for solid-state laser pumps

The development and commercial application of high power diode laser arrays for use as solid-state laser pumps is described. Such solid-state laser pumps are significantly more efficient and reliable than conventional flash-lamps. This paper describes the design and fabrication of diode lasers emitting in the 780 - 900 nm spectral region, and discusses their performance and reliability. Typical measured performance parameters include electrical-to-optical power conversion efficiencies of 50 percent, narrow-band spectral emission of 2 to 3 nm FWHM, pulsed output power levels of 50 watts/bar with reliability values of over 2 billion shots to date (tests to be terminated after 10 billion shots), and reliable operation to pulse lengths of 1 ms. Pulse lengths up to 5 ms have been demonstrated at derated power levels, and CW performance at various power levels has been evaluated in a 'bar-in-groove' laser package. These high-power 1-cm stacked-bar arrays are now being manufactured for OEM use. Individual diode laser bars, ready for package-mounting by OEM customers, are being sold as commodity items. Commercial and medical applications of these laser arrays include solid-state laser pumping for metal-working, cutting, industrial measurement and control, ranging, wind-shear/atmospheric turbulence detection, X-ray generation, materials surface cleaning, microsurgery, ophthalmology, dermatology, and dental procedures.

Linden, Kurt J.↗
NASA NTRS1986

The laser interferometer skin-friction meter - A numerical and experimental study

Limits to the applicability of thin-film lubrication theory are established. The following two problems are considered: (1) the response of the oil film to a time-varying skin friction such as is encountered in turbulent boundary layers, and (2) a 'surface-wave instability' encountered at high skin-friction levels. Results corresponding to the first problem reveal that the laser interferometer skin-friction meter may, in principle, be applied to the measurement of instantaneous skin friction. In addressing the second problem, it is shown that the observed surface waves are not the result of a hydrodynamic instability.

Murphy, J. D.↗
NASA NTRS1980

Infrared heterodyne receivers with IF responses approaching 5 GHz

Specialized coherent 10.6 micrometer infrared receivers were developed with infrared frequency responses approaching 5 GHz. Carbon dioxide lasers were employed for these applications because of their availability, stability, and high average power levels. Heterodyne receivers which employ extrinsic photoconductive Ge:Cu(Sb) mixers were developed for measurements of carbon dioxide laser scattering to determine: (1) the drive lower hybrid wave density fluctuations; and (2) the plasma ion temperature of the dense Tokamak plasmas.

Wolczok, J. M.↗
NASA NTRS1991

Laser transmitter for Lidar In-Space Technology Experiment

The Lidar In-Space Technology Experiment (LITE) Laser Transmitter Module (LTM) flight laser optical architecture has been space qualified by extensive testing at the system, subsystem and component level. The projected system output performance has been verified using an optically and electrically similar breadboard version of the laser. Parasitic lasing was closely examined and completely suppressed after design changes were implemented and tested. Oscillator and amplifier type heads were separately tested to 150 million shots. Critical subassemblies have undergone environmental testing to Shuttle qualification levels. A superior three color anti-reflection coating was developed and tested for use on 14 surfaces after the final amplifier.

Chang, John↗
DOE OSTI2026

Optical cycling on thorium monoxide for an improved test of fundamental symmetries

Optical cycling refers to repeated excitation and spontaneous emission on an electronic transition in an atom or molecule. Optical cycling in molecules can enable a wide range of quantum control and readout techniques, but unfortunately it has only been demonstrated on a small class of alkalilike or alkaline-earth-like molecules. Thorium monoxide (ThO), a molecule used in one of the most precise permanent electron electric dipole moment (eEDM) searches (ACME†) [Andreev et al., Nature (London) 562, 355 (2018)], does not fall into this category. In this work, we demonstrate the first optical cycling on this nonconventional class over a range of experimental parameter space, including laser intensity, polarization switching rate, and interaction time. We show that both the 𝐽 = 1 and 𝐽 = 2 rotational levels of ThO molecule are capable of cycling an average of 11(2) photons with a single laser, at scattering rates of 1.9⁢(6) × 10 6 and 2.3⁢(7) × 10 6 s −1 , respectively, before population is lost to other vibronic levels. We outline a scheme to apply this demonstrated optical cycling in an ACME-style eEDM measurement, improving the detection efficiency by over fourfold compared to noncycling fluorescence detection. This would lead to over a twofold enhancement in the statistical sensitivity of the eEDM search. This optical-cycling scheme can be further extended to scatter ∼100 photons, which would enable a wider range of quantum control and sensing using ThO molecules.

Atomic & molecular processes in external fields↗
DOE OSTI2022

Accelerated Scaling to Rapid Open-Air Fabrication of Durable Perovskite Solar Modules

The goals of this SETO project (DE-EE0008559, Accelerated Scaling to Rapid Open-Air Fabrication of Durable Perovskite Solar modules) are to address the principal challenges towards the successful commercialization of perovskite solar modules utilizing scalable, high-throughput open-air spray deposition. The successful outcome of the project will provide the foundation of an all open-air spray deposited perovskite solar module with hole transport layer (HTL), perovskite, electron transport layer (ETL), and barrier layer development while establishing a fundamental understanding of perovskite device behavior under accelerated aging conditions. Through this program, we have made significant progress towards a commercializable pathway for perovskites. (1) We’ve demonstrated the successful open-air deposition of perovskite and transport layer materials. These deposition methods were chosen for their inherent scalability, and open-air processing enables a significant reduction in processing costs. These methods are also compatible with high throughputs, demonstrating the fastest perovskite film deposition at these performance levels. (2) Development of a unique all-fiber laser scribing procedure provides a high-performance, low-cost method for further improvements in scalability. (3) Our group has also placed a unique emphasis on device stability. The development of testing standards for perovskite modules is required to thoroughly evaluate potential candidates for commercialization, and we’ve taken inspiration from current industry standards to provide an honest insight into the performance and reliability of our devices. (4) An extensive cost model detailing the specific contributions of each device layer and production component provides the most thorough evaluation of any perovskite technology against conventional silicon and compound semiconductor solar devices. The cost model is a critical advancement that will provide the foundation for evaluating the levelized cost of energy (LCOE) of this technology.

14 SOLAR ENERGY↗
DOE OSTI2022

Light- and Elevated-Temperature-Induced Degradation-Affected Silicon Cells From a Utility-Scale Photovoltaic System Characterized by Deep-Level Transient Spectroscopy

Photovoltaic modules from a utility-scale field experienced power loss by light- and elevated-temperature-induced degradation (LeTID). Samples from the affected monocrystalline silicon cells are cored and extracted from the module packaging and then laser-scribed to form 2-mm diameter isolated areas. Using deep-level transient spectroscopy, a majority-carrier, hole-trap defect with an activation energy of 0.42 eV is detected on degraded and regenerated samples. The LeTID-degraded sample, however, has a larger signal corresponding to a trap density of 1.1 x 10 13 cm -3 , which is about five times larger than the 2.1 x 10 12 cm -3 trap density of the regenerated sample. An increase in filling pulse time from 50 u s to 20 ms shows a slight decrease in activation energy from 0.42 to 0.36 eV suggesting that the defect level may consist of a band of energy states where shallower states continue to fill with long filling times. The capture rate of the defect is directly measured using an increasing series of filling pulsewidths in 15 to 125 ns range. This leads to a measured capture cross section of 5.1 x 10 -17 cm 2 , and using an approximate defect density of 10 13 cm -3 , the majority-carrier-hole lifetime related to this defect is approximately 100 u s when in the LeTID-degraded state.

charge carrier lifetime↗
NASA NTRS2008

Interferometric Testbed for Nanometer Level Stabilization of Environmental Motion Over Long Timescales

We developed an interferometric testbed to stabilize environmental motions over timescales of several hours and a lengthscale of 1m. Typically, thermal and seismic motions on the ground are larger than 1 micron over these scales, affecting the precision of more sensitive measurements. To suppress such motions, we built an active stabilization system composed of interferometric sensors, a hexapod actuator, and a frequency stabilized laser. With this stabilized testbed, environmental motions were suppressed down to nm level. This system will allow us to perform sensitive measurements, such as ground testing of LISA (Laser Interferometer Space Antenna), in the presence of environmental noise.

Numata, Kenji↗
NASA NTRS1985

High-power diode lasers for optical communications applications

High-power, single-mode, double-heterojunction AlGaAs diode lasers are being developed to meet source requirements for both fiber optic local area network and free space communications systems. An individual device, based on the channeled-substrate-planar (CSP) structure, has yielded single spatial and longitudinal mode outputs of up to 90 mW CW, and has maintained a single spatial mode to 150 mW CW. Phase-locked arrays of closely spaced index-guided lasers have been designed and fabricated with the aim of multiplying the outputs of the individual devices to even higher power levels in a stable, single-lobe, anastigmatic beam. The optical modes of the lasers in such arrays can couple together in such a way that they appear to be emanating from a single source, and can therefore be efficiently coupled into optical communications systems. This paper will review the state of high-power laser technology and discuss the communication system implications of these devices.

Carlin, D. B.↗
NASA NTRS1992

A dual purpose optical truss laser metrology system for a space-based far-IR segmented telescope: Figure maintenance and pointing control

To obtain imaging performance as for monolithic mirrors, large segmented reflectors used for astronomy must be actively aligned and pointed to extreme levels of precision. A system concept for a dual purpose optical truss laser metrology system is described which is used for both figure and alignment maintenance and telescope pointing. A two-stage figure active control approach was developed for several proposed spaceborne far infrared segmented telescopes, one of which is the 10-20 meters Large Deployable Reflector (LDR). The first active control stage, the figure initialization control system, aligns the optical elements (i.e., the primary segments, secondary and focal plane assembly) based on images obtained. The second stage, the figure maintenance control system, maintains the alignment between re-initializations using measurements provided by laser interferometers arranged in an optical truss configuration. It measures the relative positions and alignments of the telescope segments so that a controller can reposition them appropriately. The application of this optical truss for figure maintenance control is the subject of the first part of this paper. The second portion of this paper discusses the application of the optical truss to telescope pointing. Here, the laser metrology system is used to transfer pointing information from an external fine guidance sensor (FGS) to the telescope optical boresight as defined by the primary mirror, secondary mirror, and focal plane assembly. Thus, any alignment variations between the two boresights can be observed and accounted for.

Lau, Kenneth↗