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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 739 records · Page 41
All sourcesNASA NTRSDOE OSTI
NASA NTRS2014

Characteristics of the Single-Longitudinal-Mode Planar-Waveguide External Cavity Diode Laser at 1064 nm

We describe the characteristics of the planar-waveguide external cavity diode laser (PW-ECL). To the best of our knowledge, it is the first butterfly-packaged 1064-nm semiconductor laser that is stable enough to be locked to an external frequency reference. We evaluated its performance from the viewpoint of precision experiments. Especially, using a hyperfine absorption line of iodine, we suppressed its frequency noise by a factor of up to104 at 10 mHz. The PW-ECLs compactness and low cost make it a candidate to replace traditional Nd:YAGnon-planar ring oscillators and fiber lasers in applications which require a single longitudinal-mode.

diode↗
NASA NTRS2013

Real-Tme Boron Nitride Erosion Measurements of the HiVHAc Thruster via Cavity Ring-Down Spectroscopy

Cavity ring-down spectroscopy was used to make real-time erosion measurements from the NASA High Voltage Hall Accelerator thruster. The optical sensor uses 250 nm light to measure absorption of atomic boron in the plume of an operating Hall thruster. Theerosion rate of the High Voltage Hall Accelerator thruster was measured for discharge voltages ranging from 330 to 600 V and discharge powers ranging from 1 to 3 kW. Boron densities as high as 6.5 x 10(exp 15) per cubic meter were found within the channel. Using a very simple boronvelocity model, approximate volumetric erosion rates between 5.0 x 10(exp -12) and 8.2 x 10(exp -12) cubic meter per second were found.

Hall thruster↗
NASA NTRS2014

Characteristics of the Single-Longitudinal-Mode Planar-Waveguide External Cavity Diode Laser at 1064 nm

We describe the characteristics of the planar-waveguide external cavity diode laser (PW-ECL). To the best of our knowledge, it is the first butterfly-packaged 1064 nm semiconductor laser that is stable enough to be locked to an external frequency reference. We evaluated its performance from the viewpoint of precision experiments. Using a hyperfine absorption line of iodine, we suppressed its frequency noise by a factor of up to 104 at 10 mHz. The PWECL's compactness and low cost make it a candidate to replace traditional Nd:YAG nonplanar ring oscillators and fiber lasers in applications that require a single longitudinal mode.

planar-waveguide↗
NASA NTRS2011

Whispering Gallery Mode Resonators as Optical Reference Cavities

Highly stabilized lasers are an increasingly valuable tool for metrology. For many applications, however, existing Fabry Perot systems are too bulky and cumbersome. We are investigating the use of miniature monolithic whispering gallery mode resonators as reference cavities for laser stabilization. We seek to exploit the benefit of small size and vibration resistance by suppressing thermally induced frequency fluctuations. We have theoretically investigated the viability of using a thin-film coating to achieve temperature compensation. We have experimentally investigated an active temperature stabilization scheme based on birefringence in a crystalline resonator. We also report progress of laser locking to the resonators.

optical frequency↗
NASA NTRS2011

Flight-Like Optical Reference Cavity for GRACE Follow-On Laser Frequency Stabilization

We describe a prototype optical cavity and associated optics that has been developed to provide a stable frequency reference for a future space-based laser ranging system. This instrument is being considered for inclusion as a technology demonstration on the recently announced GRACE follow-on mission, which will monitor variations in the Earth's gravity field.

Gravity Recovery and Climate Experiment (GRACE)↗
NASA NTRS2017

Saturn's Rings and Associated Ring Plasma Cavity: Evidence for Slow Ring Erosion

We re-examine the radio and plasma wave observations obtained during the Cassini Saturn orbit insertion period, as the spacecraft flew over the northern ring surface into a radial distance of 1.3 Rs (over the C-ring). Voyager era studies suggest the rings are a source of micro-meteoroid generated plasma and dust, with theorized peak impact-created plasma outflows over the densest portion of the rings (central B-ring). In sharp contrast, the Cassini Radio and Plasma Wave System (RPWS) observations identify the presence of a ring-plasma cavity located in the central portion of the B-ring, with little evidence of impact-related plasma. While previous Voyager era studies have predicted unstable ion orbits over the C- ring, leading to field-aligned plasma transport to Saturns ionosphere, the Cassini RPWS observations do not reveal evidence for such instability-created plasma fountains. Given the passive ring loss processes observed by Cassini, we find that the ring lifetimes should extend >10(exp 9) years, and that there is limited evidence for prompt destruction (loss in <100 Myrs).

Plasma↗
NASA NTRS2018

The Complex Morphology of the Young Disk MWC 758: Spirals and Dust Clumps around a Large Cavity

We present Atacama Large Millimeter Array observations at an angular resolution of 0 1 - 0 2 of the disk surrounding the young Herbig Ae star MWC758. The data consist of images of the dust continuum emission recorded at 0.88 millimeter, as well as images of the 13CO and C18O J = 3-2 emission lines. The dust continuum emission is characterized by a large cavity of roughly 40 au in radius which might contain a mildly inner warped disk. The outer disk features two bright emission clumps at radii of ~47 and 82 au that present azimuthal extensions and form a double-ring structure. The comparison with radiative transfer models indicates that these two maxima of emission correspond to local increases in the dust surface density of about a factor 2.5 and 6.5 for the south and north clumps, respectively. The optically thick 13CO peak emission, which traces the temperature, and the dust continuum emission, which probes the disk mid plane, additionally reveal two spirals previously detected in near-IR at the disk surface. The spirals seen in the dust continuum emission present, however, a slight shift of a few au toward larger radii and one of the spirals crosses the south dust clump. Finally, we present different scenarios to explain the complex structure of the disk.

Atacama Large Millimeter Array↗
NASA NTRS2019

Cavity Environmental Control System Upgrade for NASA's Stratospheric Observatory for Infrared Astronomy

The main goal of this project is to fulfill the need of a controller upgrade for the Cavity Environmental Control System (CECS) on the NASA SOFIA aircraft. The preceding controller had multiple disadvantages including operating in an unpressurized region, incomplete functionality implementation, limited fault and status monitoring capability, and reduced maintainability and reliability. The new controller will go through the NASA design process to fulfill all the requirements of CECS operation including complete functionality of all devices currently installed on the aircraft, added devices to improve fault and health monitoring, and overall improvement in maintainability and reliability.

Al-Hajjeh, Ashraf A.↗
NASA NTRS2020

A Cavity-Enhanced UV Absorption Instrument for High-Precision, Fast-Time-Response Ozone Measurements

The NASA Rapid Ozone Experiment (ROZE) is a broadbandcavity-enhanced UV absorption instrument for the detection of in situozone (O3).ROZE uses an incoherent LED light source coupled to a high-finesse optical cavity to achieve an effective pathlength of ~104 m. Due to its high-sensitivity and smalloptical cell volume, ROZE demonstratesa 1𝜎precision of 80 pptv (0.1 s) and 31 pptv (1 s), as well as an 𝑒-fold timeresponseof 50 ms. ROZE can be operated in a range of field environments, including low-and high-altitude research aircraft,and is particularly suited toO3vertical flux measurements usingthe eddy covariance technique.ROZE was successfully integrated aboard the NASA DC-8 aircraft during July–September2019and validated against a well-established chemiluminescence measurement of O3.Aflight within the marine boundary layer also demonstrated flux measurement capabilities, and we observeda mean O3deposition velocityof 0.029 ± 0.005 cm s–1to the ocean surface.The performance characteristics detailed below make ROZE a robust, versatile instrument for fieldmeasurements of O3.

Rapid Ozone Experiment (ROZE)↗
NASA NTRS2021

On Parametric Generation of Deep UV Light in Monolithic Cavities With Cubic Nonlinearity

Coherent ultra violet (UV) light has broad applications in optical atomic clocks and quantum computers. Since availability of semiconductor tunable monochromatic lasers is limited at short wavelengths, optical nonlinear processes are frequently used to produce the desirable radiation wavelength. Optical crystals with quadratic nonlinearity are promising for this purpose because of their transparency and high optical damage threshold. In this paper we discuss a possibility of generation of coherent deep UV light utilizing high quality factor (-Q) monolithic optical microcavities made of crystalline optical materials characterized with cubic nonlinearities. We show that the generation is feasible in spite of the relatively small cubic nonlinearities, due to the ultra-broad-band high optical transparency of the crystals and associated high-Q achievable in the cavities created out of the materials. We found that the birefringence as well as the tensor nature of the nonlinear susceptibility of the crystalline optical materials can simplify the phase matching of the nonlinear processes.

Matsko, A.B.↗
NASA NTRS2023

Cavity Ring-Down Spectroscopy of Anthracene, 9-Methylanthracene, and 2 Methylanthracene in Supersonic Expansion

The S0–S1 absorption spectra of anthracene (C14H10), 9-methylanthracene (C15H12), and 2-methylanthracene (C15H12) are measured in the ultraviolet region between 330 and 375 nm (26,666 to 30,303 cm–1) with cavity ring-down spectroscopy in supersonic free-jet expansions of argon. The associated vibronic band systems and their spectroscopic assignments are discussed and compared to previous studies performed using fluorescence excitation and dispersed fluorescence techniques. Density functional theory (DFT) calculations were carried out to study the structures and evaluate the vibrational transitions of the ground and excited states. Time-dependent DFT calculations of the first electronic excited states and Franck–Condon factor calculations were carried out to assist in the assignment of the experimentally measured vibronic bands. The vibronic spectra obtained in absorption agree well with fluorescence excitation spectra in terms of peak positions but exhibit different relative band intensities. We find a very good match between experimentally obtained vibronic line positions and the peak positions of the quantum chemically calculated Franck–Condon excitation lines.

Salma Bejaoui↗
NASA NTRS2011

Exact Cavity Perturbation Technique to Determine Complex Permittivity of Dielectric Materials

Cassini is an international spacecraft mission facilitated by NASA and ESA which seeks to understand the Saturn planetary system, including rings and moons. Launched in 1997, the Cassini spacecraft contains two major components: the Cassini orbiter that has been orbiting Saturn since October 2004, and the European-built Huygens probe that landed on Titan's surface in December 2004 to study its geology and atmosphere. Titan, Saturn's largest moon and the second largest moon in the solar system, possesses surface and atmospheric features similar to those of Earth, including lakes, seas, and mountains. A physical characterization of these features is critical to understanding the origin and evolution of Titan, whose surface composition reflects its geological history. Because Titan's atmosphere is largely composed of methane, it is believed that surfaces lakes are filled with mixtures of liquid hydrocarbons. The Cassini orbiter's RADAR instrument has been scanning Titan's surface at the atmosphere-penetrating microwave frequency of 13.8 Gigahertz since 2004. However, accurate interpretation of these data is limited by a lack of knowledge regarding dielectric properties of liquid hydrocarbons at cryogenic temperatures. Therefore, it is of specific interest to experimentally determine values for the complex permittivities of various liquid hydrocarbon mixtures at the surface conditions of Titan. In particular, more accurate values for complex permittivity would improve estimates of lake depth and surface composition obtained from the instrument's altimetry and backscatter modes.

dielectric constant↗