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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 NTRS1991

Efficient second-harmonic conversion of CW single-frequency Nd:YAG laser light by frequency locking to a monolithic ring frequency doubler

Efficient second-harmonic conversion of the 1064-nm output of a diode-pumped CW single-frequency Nd:YAG laser to 532 nm was obtained by frequency locking the laser to a monolithic ring resonator constructed of magnesium-oxide-doped lithium niobate. The conversion efficiency from the fundamental to the second harmonic was 65 percent. Two hundred milliwatts of CW single-frequency 532-nm light were produced from 310 mW of power of 1064-nm light. This represents a conversion efficiency of 20 percent from the 1-W diode laser used to pump the Nd:YAG laser to single-frequency 532-nm output. No signs of degradation were observed for over 500 h of operation.

Gerstenberger, D. C.↗
NASA NTRS2011

System and method for tuning adjusting the central frequency of a laser while maintaining frequency stabilization to an external reference

A method and system for stabilizing a laser to a frequency reference with an adjustable offset. The method locks a sideband signal generated by passing an incoming laser beam through the phase modulator to a frequency reference, and adjusts a carrier frequency relative to the locked sideband signal by changing a phase modulation frequency input to the phase modulator. The sideband signal can be a single sideband (SSB), dual sideband (DSB), or an electronic sideband (ESB) signal. Two separate electro-optic modulators can produce the DSB signal. The two electro-optic modulators can be a broadband modulator and a resonant modulator. With a DSB signal, the method can introduce two sinusoidal phase modulations at the phase modulator. With ESB signals, the method can further drive the optical phase modulator with an electrical signal with nominal frequency OMEGA(sub 1) that is phase modulated at a frequency OMEGA(sub 2)

Livas, Jeffrey↗
NASA NTRS1990

Monitoring of catalyst performance in CO2 lasers using frequency modulation spectroscopy with diode lasers

Closed-cycle CO2 laser operation with removal of O2 and regeneration of CO2 can be achieved by catalytic CO-O2 recombination. Both parametric studies of the optimum catalyst formulation and long-term performance tests require on line monitoring of CO, O2 and CO2 concentrations. There are several existing methods for molecular oxygen detection. These methods are either intrusive (such as electrochemical method or mass spectrometry) or very expensive (such as CARS, UV laser absorption). Researchers demonstrated a high-sensitivity spectroscopic measurement of O2 using the two-tone frequency modulation spectroscopy (FMS) technique with a near infrared GaAlAs diode laser. Besides its inexpensive cost, fast response time, nonintrusive measurements and high sensitivity, this technique may also be used to differentiate between isotopes due to its high spectroscopic resolution. This frequency modulation spectroscopy technique could also be applied for the on-line monitoring of CO and CO2 using InGaAsP diode lasers operation in the 1.55 microns region and H2O in the 1.3 microns region. The existence of single mode optical fibers at the near infrared region makes it possible to combine FMS with optical fiber technology. Optical fiber FMS is particularly suitable for making point-measurements at one or more locations in the CO2 laser/catalyst system.

Wang, Liang-Guo↗
NASA NTRS1986

Frequency domain laser velocimeter signal processor

A laser velocimeter frequency domain signal processor is described which utilizes smart instrumentation to configure itself to maximize measurement accuracy based on the determined characteristics of the input signals. The stystem provides the same measurement capabilities as the high-speed burst counter in instantaneous measurements of signal frequency, the same automatic gain control and automatic frequency control as the frequency tracker, and the same immunity to signal-to-noise derived errors as the photon correlator. Simulation results demonstrate measurement accuracies of better than 0.2 percent for signal frequencies up to 100 MHz.

Meyers, J. F.↗
NASA NTRS1990

Scientific applications of frequency-stabilized laser technology in space

A synoptic investigation of the uses of frequency-stabilized lasers for scientific applications in space is presented. It begins by summarizing properties of lasers, characterizing their frequency stability, and describing limitations and techniques to achieve certain levels of frequency stability. Limits to precision set by laser frequency stability for various kinds of measurements are investigated and compared with other sources of error. These other sources include photon-counting statistics, scattered laser light, fluctuations in laser power, and intensity distribution across the beam, propagation effects, mechanical and thermal noise, and radiation pressure. Methods are explored to improve the sensitivity of laser-based interferometric and range-rate measurements. Several specific types of science experiments that rely on highly precise measurements made with lasers are analyzed, and anticipated errors and overall performance are discussed. Qualitative descriptions are given of a number of other possible science applications involving frequency-stabilized lasers and related laser technology in space. These applications will warrant more careful analysis as technology develops.

Schumaker, Bonny L.↗
NASA NTRS1974

Stabilizing a gaseous optical laser

Frequency of gaseous optical laser can be stabilized by sinusoidally modulating the geometry of the cavity. Fabry-Perot dielectric mirrors are mounted in two Invar blocks that are connected by four magnetorestrictive bars. Each bar has three coils to sinusoidally modulate system. Ac establishes frequency, and dc the average value; both are supplied to coil from control system.

Jauan, A.↗
NASA NTRS2012

Estimation of Frequency Noise in Semiconductor Lasers Due to Mechanical Thermal Noise

We evaluate mechanical thermal noise in semiconductor lasers, applying a methodology developed for fixed-spacer cavities for laser frequency stabilization. Our simple model determines an underlying fundamental limit for the frequency noise of free-running semiconductor laser, and provides a framework: where the noise may be potentially reduced with improved design.

Numata, Kenji↗
NASA NTRS1996

Experiments with Lasers and Frequency Doublers

Solid state laser sources, such as diode-pumped Nd:YAG lasers, have given us CW laser light of high power with unprecedented stability and low noise performance. In these lasers most of the technical sources of noise can be eliminated allowing them to be operated close to the theoretical noise limit set by the quantum properties of light. The next step of reducing the noise below the standard limit is known as squeezing. We present experimental progress in generating reliably squeezed light using the process of frequency doubling. We emphasize the long term stability that makes this a truly practical source of squeezed light. Our experimental results match noise spectra calculated with our recently developed models of coupled systems which include the noise generated inside the laser and its interaction with the frequency doubler. We conclude with some observations on evaluating quadrature squeezed states of light.

Bachor, H.-A.↗
NASA NTRS2008

LISA Technology Development at GSFC

The prime focus of LISA technology development efforts at NASA/GSFC has been in LISA interferometry, specifically in the area of laser frequency noise mitigation. Laser frequency noise is addressed through a combination of stabilization and common-mode rejection. Current plans call for two stages of stabilization, pre-stabilization to a local frequency reference and further stabilization using the constellation as a frequency reference. In order for these techniques to be used simultaneously, the pre-stabilization step must provide an adjustable frequency offset. Here, we report on a modification to the standard modulation/demodulation techniques used to stabilize to optical cavities that generates a frequency-tunable reference from a fixed-length cavity. This technique requires no modifications to the cavity itself and only minor modifications to the components. The measured noise performance and dynamic range of the laboratory prototype meets the LISA requirements.

Thorpe, James Ira↗
NASA NTRS2008

LISA Beyond Einstein: From the Big Bang to Black Holes. LISA Technology Development at GSFC

This viewgraph presentation reviews the work that has been ongoing at the Goddard Space Flight Center (GSFC) in the development of the technology to be used in the Laser Interferometer Space Antenna (LISA) spacecrafts. The prime focus of LISA technology development efforts at NASA/GSFC has been in LISA interferometry. Specifically efforts have been made in the area of laser frequency noise mitigation. Laser frequency noise is addressed through a combination of stabilization and common-mode rejection. Current plans call for two stages of stabilization, pre-stabilization to a local frequency reference and further stabilization using the constellation as a frequency reference. In order for these techniques to be used simultaneously, the pre-stabilization step must provide an adjustable frequency offset. This presentation reports on a modification to the standard modulation/demodulation technique used to stabilize to optical cavities that generates a frequency-tunable reference from a fixed length cavity. This technique requires no modifications to the cavity itself and only minor modifications to the components. The measured noise performance and dynamic range of the laboratory prototype meet the LISA requirements.

Thorpe, James Ira↗
NASA NTRS1993

Diode-Pumped, Q-Switched, Frequency-Doubling Laser

Experimental Q-switched, diode-pumped, intracavity-frequency-doubling laser generates pulses of radiation at wavelength of 532 nm from excitation at 810 nm. Principal innovative feature distinguishing laser from others of its type: pulsed operation of laser at pulse-repetition frequencies higher than reported previously. Folded resonator keeps most of second-harmonic radiation away from Q-switcher, laser crystal, and laser diodes. Folding mirror highly reflective at fundamental laser wavelength and highly transmissive at second-harmonic laser wavelength. By virtue of difference of about 0.6 percent between reflectivities in two polarizations at fundamental wavelength, folding mirror favors polarized oscillation at fundamental wavelength. This characteristic desirable for doubling of frequency in some intracavity crystals.

Hemmati, Hamid↗