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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

High-bandwidth image-based predictive laser stabilization via optimized Fourier filters

Controlling the delivery of kHz-class pulsed lasers is of interest in a variety of industrial and scientific applications, from next-generation laser-plasma acceleration to laser-based x-ray emission and high-precision manufacturing. The transverse position of the laser pulse train on the application target is often subject to fluctuations by external drivers (e.g., room cooling and heating systems, motorized optics stages and mounts, vacuum systems, chillers, and/or ground vibrations). For typical situations where the disturbance spectrum exhibits discrete peaks on top of a broad-bandwidth lower-frequency background, traditional PID (proportional-integral-derivative) controllers may struggle, since as a general rule PID controllers can be used to suppress vibrations up to only about 5%–10% of the sampling frequency. Here, a predictive feed-forward algorithm is presented that significantly enhances the stabilization bandwidth in such laser systems (up to the Nyquist limit at half the sampling frequency) by online identification and filtering of one or a few discrete frequencies using optimized Fourier filters. Furthermore, the system architecture demonstrated here uses off-the-shelf CMOS cameras and piezo-electric actuated mirrors connected to a standard PC to process the alignment images and implement the algorithm. To avoid high-end, high-cost components, a machine-learning-based model of the piezo mirror’s dynamics was integrated into the system, which enables high-precision positioning by compensating for hysteresis and other hardware-induced effects. A successful demonstration of the method was performed on a 1 kHz laser pulse train, where externally-induced vibrations of up to 400 Hz were attenuated by a factor of five, far exceeding what could be done with a standard PID scheme.

Natal, Joseph↗
NASA NTRS2008

Frequency-tunable Pre-stabilized Lasers for LISA via Sideband-locking

Laser frequency noise mitigation is one of the most challenging aspects of the LISA interferometric measurement system. The unstabilized frequency fluctuations must be suppressed by roughly twelve orders of magnitude in order to achieve stability sufficient for gravitational wave detection. This enormous suppression will be achieved through a combination of stabilization and common-mode rejection. The stabilization component will itself be achieved in two stages: pre-stabilization to a local optical cavity followed by arm-locking to some combination of the inter-spacecraft distances. In order for these two stabilization stages to work simultaneously, the lock-point of the pre-stabilization loop must be frequency tunable. The current baseline stabilization technique, locking to an optical cavity, does not provide tunability between cavity resonances, which are typically spaced by 100s of MHz. Here we present a modification to the traditional Pound-Drever-Hall cavity locking technique that allows the laser to be locked to a cavity resonance with an adjustable frequency offset. This technique requires no modifications to the optical cavity itself, thus preserving the stability of the frequency reference. We present measurements of the system performance and demonstrate that we can meet implement the first two stages of stabilization.

Livas, Jeffrey C.↗
NASA NTRS2008

Frequency-Tuneable Pre-Stabilized Lasers for LISA via Sideband Locking

Laser frequency noise mitigation is one of the most challenging aspects of the LISA interferometric measurement system. The unstabilized frequency fluctuations must be suppressed by roughly twelve orders of magnitude in order to achieve a stability sufficient for gravitational wave detection. This enormous suppression will be achieved through a combination of stabilization and common-mode rejection. The stabilization component will itself be achieved in two stages: pre-stabilization to a local optical cavity followed by arm-locking to some combination of the inter-spacecraft distances. In order for these two stabilization stages to work simultaneously, the lock-point of the pre-stabilization loop must be frequency tunable. The current baseline stabilization technique, locking to an optical cavity, does not provide tunability between cavity resonance, which are typically spaced by 100s of MHz. Here we present a modification to the traditional Pound-Drever-Hall cavity locking technique that allows the laser to be locked to a cavity resonance with an adjustable frequency offset. This technique requires no modifications to the optical cavity itself, thus preserving the stability of the frequency reference. We present measurements of the system stability, demonstrating that the pre-stabilization level satisfies LISA requirements. We also present a demonstration of a phase-lock loop which utilizes the tunable sideband locking technique as a pre-stabilizations tage. The performance of the pre-stabilized phase-lock-loop indicates that the tunable sideband technique will meet the requirements as an actuator for arm-locking in LISA.

Thorpe, James Ira↗
NASA NTRS2000

High-Q Microsphere Cavity for Laser Stabilization and Optoelectronic Microwave Oscillator

With submillimeter size and optical Q up to approximately 10 (exp 10), microspheres with whispering-gallery (WG) modes are attractive new component for fiber-optics/photonics applications and a potential core in ultra-compact high-spectral-purity optical and microwave oscillators. In addition to earlier demonstrated optical locking of diode laser to WG mode in a microsphere, we report on microsphere application in the microwave optoelectronic oscillator, OEO. In OEO, a steady-state microwave modulation of optical carrier is obtained in a closed loop including electro-optical modulator, fiber-optic delay, detector and microwave amplifier. OEO demonstrates exceptionally low phase noise (-140 dBc/Hz at l0kHz from approximately 10GHz carrier) with a fiber length approximately 2km. Current technology allows to put all parts of the OEO, except the fiber, on the same chip. Microspheres, with their demonstrated Q equivalent to a kilometer fiber storage, can replace fiber delays in a truly integrated device. We have obtained microwave oscillation in microsphere-based OEO at 5 to 18 GHz, with 1310nm and 1550nm optical carrier, in two configurations: 1) with external DFB pump laser, and 2) with a ring laser including microsphere and a fiber optic amplifier. Also reported is a simple and efficient fiber coupler for microspheres facilitating their integration with existing fiber optics devices.

Ilchenko, Vladimir S.↗
NASA NTRS1967

Design concepts using ring lasers for frequency stabilization

Laser frequency stabilization methods are based on a frequency discriminant which generates an unambiguous deviation signal used for automatic stabilization. Closed-loop control stabilizes cavity length at a null point. Some systems have a stabilized ring laser using a piezoelectric dither and others use a Doppler gain tube.

Mocker, H.↗
NASA NTRS1991

Cryogenic radiometers and intensity-stabilized lasers for Eos radiometric calibrations

Liquid helium-cooled electrical substitution radiometers (ESRs) provide irradiance standards with demonstrated absolute accuracy at the 0.01 percent level, spectrally flat response between the UV and IR, and sensitivity down to 0.1 nW/sq cm. We describe an automated system developed for NASA - Goddard Space Flight Center, consisting of a cryogenic ESR illuminated by servocontrolled laser beams. This system is designed to provide calibration of single-element and array detectors over the spectral range between 257nm in the UV to 10.6 microns in the IR. We also describe a cryogenic ESR optimized for black body calibrations that has been installed at NIST, and another that is under construction for calibrations of the CERES scanners planned for Eos.

Foukal, P.↗
NASA NTRS1999

High-Q Microsphere Cavity for Laser Stabilization and Optoelectronic Microwave

With submillimeter size and optical Q up to ~ 10(sup 10), microspheres with whispering-gallery (WG) modes are attractive new component for fiber-optics/photonics applications and a potential core in ultra-compact high-spectral-purity optical and microwave oscillators.

microspheres fiber optics microwave photonics↗
NASA NTRS1992

Diode-laser frequency stabilization based on the resonant Faraday effect

The authors present the results of a method for frequency stabilizing laser diodes based on the resonant Faraday effects. A Faraday cell in conjunction with a polarizer crossed with respect to the polarization of the laser diode comprises the intracavity frequency selective element. In this arrangement, a laser pull-in range of 9 A was measured, and the laser operated at a single frequency with a linewidth less than 6 MHz.

Wanninger, P.↗
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 NTRS1973

The CO2 laser frequency stability measurements

Carbon dioxide laser frequency stability data are considered for a receiver design that relates to maximum Doppler frequency and its rate of change. Results show that an adequate margin exists in terms of data acquisition, Doppler tracking, and bit error rate as they relate to laser stability and transmitter power.

Johnson, E. H., Jr.↗
NASA NTRS1966

Frequency-Stabilized CO2 Lasers, Phase I

Frequency-stabilized carbon dioxide laser - electronic and mechanical stabilization schemes, control loop techniques, wavelength and mode control, and general laser construction

CARBON DIOXIDE↗
NASA NTRS2005

Laser frequency stabilization for LISA

The requirement on laser frequency noise in the Laser Interferometer Space Antenna (LISA) depends on the velocity and our knowledge of the position of each spacecraft of the interferometer. Currently it is assumed that the lasers must have a pre-stabilized frequency stability of 30Hz/square root of Hz over LISA'S most sensitive frequency band (3 mHz - 30 mHz). The intrinsic frequency stability of even the most stable com- mercial lasers is several orders of magnitude above this level. Therefore it is necessary to stabilize the laser frequency to an ultra-stable frequency reference which meets the LISA requirements. The baseline frequency reference for the LISA lasers are high finesse optical cavities based on ULE spacers. We measured the stability of two ULE spacer cavities with respect to each other. Our current best results show a noise floor at, or below, 30 Hz/square root of Hz above 3 mHz. In this report we describe the experimental layout of the entire experiment and discuss the limiting noise sources.

Mueller, Guido↗