Search NASA⌕ Search

SEARCH · Search NASA

Results for “laser cavities”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Coherent lidars based on intracavity heterodyning of echo signals

The development and technical realization of the method of laser sounding of the atmosphere based on the effects of mixing of reference and external fields of scattering inside a laser cavity are presented. An approximate theory of the method was developed on the basis of the investigations using the model of a three-mirror laser. The nonlinear effect of a wideband laser on frequency-dependent external influences of the atmosphere was investigated. The field measurements of gaseous composition of the atmosphere were performed on the basis of a given method of coherent reception using a tunable CO2 laser.

Zuev, V. E.↗
NASA NTRS2010

Fiber-Based Lasers as an Option for GRACE Follow-On Light Source

Fiber based lasers offer a number of attractive characteristics for space application: state of the art laser technology, leverage of design and reliability from the substantial investments of the telecon industry, and convenient redundancy of higher risk components through fiber splicing. At NASA/Goddard we are currently investigating three GFO fiber-based laser options: a fiber oscillator built in our laboratory; an effort to space qualify a commercial design that uses a proprietary high-gain fiber cavity; and the space qualification of a promising new commercial external cavity laser, notable for its low-mass, compact design. In my talk I will outline these efforts, and suggest that the GFO Project may soon have the option of a US laser vendor for its light source.

Camp, Jordan↗
NASA NTRS1986

Pulsed mononode dye laser developed for a geophysical application

Following the extension of the lidar technique in the study of the atmosphere, the necessity of having a high power pulsed laser beam with a narrowed bandwidth and the possibility of selecting a particular wavelength within a certain spectral region arises. With the collaboration of others, a laser cavity using the multiwave Fizeau wedge (MWFW) was developed. Using the classical method of beam amplification with the aid of different stages, a new pulsed dye laser device was designed. The originality resides in the use of reflecting properties of the MFWF. Locally a plan wave coming with a particular angular incidence is reflected with a greater than unity coefficient; this is the consequence of the wedge angle which doubles the participation of every ray in the interferometric process. This dye laser operation and advantages are discussed. The feasibility of different geophysical applications envisageable with this laser is discussed.

Jegou, J. P.↗
NASA NTRS1980

Widely tunable (PbSn)Te lasers using etched cavities for mass production

Lead salt diode lasers are being used increasingly as tunable sources of monochromatic infrared radiation in a variety of spectroscopic systems. These devices are particularly useful, both in the laboratory and in the field, because of their high spectral brightness (compared to thermal sources) and wide spectral coverage (compared to line-tunable gas lasers). While the primary commercial application of these lasers has been for ultrahigh resolution laboratory spectroscopy, there are numerous systems applications, including laser absorbtion pollution monitors and laser heterodyne radiometers, for which diode lasers have great potential utility. Problem areas related to the wider use of these components are identified. Among these are total tuning range, mode control, and high fabrication cost. A fabrication technique which specifically addresses the problems of tuning range and cost, and which also has potential application for mode control, is reported.

Miller, M. D.↗
NASA NTRS1993

Laser with optically driven Q-switch

An optically driven interactive Q-switch, i.e., a Q-switch that responds to a short pulse of light, for example, from external light-emitting diodes (LEDs) or diode lasers, is provided for producing an output laser pulse from electronic energy stored in a laser medium. Q-switching is thus achieved on demand by electrically pulsing the light source to produce a pulse of light directed onto a Q-switch medium in the laser cavity. Electronic control of the light pulse from the external source will thus provide not only efficient Q-switching frequency but also independent control of output laser pulse width with a fast rise time for each output laser pulse.

Hemmati, Hamid↗
NASA NTRS1995

Laser with optically driven Q-switch

An optically driven interactive Q-switch, i.e., a Q-switch that responds to a short pulse of light, for example, from external light-emitting diodes (LED's) or diode lasers, is provided for producing an output laser pulse from electronic energy stored in a laser medium. Q-switching is thus achieved on demand by electrically pulsing the light source to produce a pulse of light directed onto a Q-switch medium in the laser cavity. Electronic control of the light pulse from the external source will thus provide not only efficient Q-switching frequency but also independent control of output laser pulse width with a fast rise time for each output laser pulse.

Hemmati, Hamid↗
DOE OSTI2020

In-situ measurement of pyrolysis and combustion gases from biomass burning using swept wavelength external cavity quantum cascade lasers

Broadband high-speed absorption spectroscopy using swept-wavelength external cavity quantum cascade lasers (ECQCLs) is applied to measure multiple pyrolysis and combustion gases in biomass burning experiments. Two broadly-tunable swept-ECQCL systems were used, with the first tuned over a range of 2089-2262 cm -1 (4.42 – 4.79 µm) to measure spectra of CO 2 , H 2 O, and CO. The second was tuned over a range of 920-1150 cm -1 (8.70 – 10.9 µm) to measure spectra of ammonia (NH 3 ), ethene (C 2 H 4 ), and methanol (MeOH). Absorption spectra were measured continuously at a 100 Hz rate throughout the burn process, including inhomogeneous flame regions, and analyzed to determine time-resolved gas concentrations and temperature. The results provide in-situ, dynamic information regarding gas-phase species as they are generated, close to the biomass fuel source.

09 BIOMASS FUELS↗
NASA NTRS2004

Thermal Noise Limit in Frequency Stabilization of Lasers with Rigid Cavities

We evaluated thermal noise (Brownian motion) in a rigid reference cavity used for frequency stabilization of lasers, based on the mechanical loss of cavity materials and the numerical analysis of the mirror-spacer mechanics with t.he direct application of the fluctuation dissipation theorem. This noise sets a fundamental limit for the frequency stability achieved with a rigid frequency- reference cavity of order 1 Hz/square root Hz(0.01 Hz/square root Hz) at 10 mHz (100 Hz) at room temperature. This level coincides with the world-highest level stabilization results.

Numata, Kenji↗
NASA NTRS2005

Thermal Noise Limit in Frequency Stabilization of Lasers with Rigid Cavities

We evaluated thermal noise (Brownian motion) in a rigid reference cavity Used for frequency stabilization of lasers, based on the mechanical loss of cavity materials and the numerical analysis of the mirror-spacer mechanics with the direct application of the fluctuation dissipation theorem. This noise sets a fundamental limit for the frequency stability achieved with a rigid frequency-reference cavity of order 1 Hz/rtHz at 10mHz at room temperature. This level coincides with the world-highest level stabilization results.

Numata, Kenji↗
DOE OSTI2020

Integrated dispersion compensated mode-locked quantum dot laser

Quantum dot lasers are excellent on-chip light sources, offering high defect tolerance, low threshold, low temperature variation, and high feedback insensitivity. Yet a monolithic integration technique combining epitaxial quantum dot lasers with passive waveguides has not been demonstrated and is needed for complex photonic integrated circuits. We present here, for the first time to our knowledge, a monolithc offset quantum dot integration platform that permits formation of a laser cavity utilizing both the robust quantum dot active region and the versatility of passive GaAs waveguide structures. This platform is substrate agnostic and therefore compatible with the quantum dot lasers directly grown on Si. As an illustration of the potential of this platform, we designed and fabricated a 20 GHz mode-locked laser with a dispersion-engineered on-chip waveguide mirror. Due to the dispersion compensation effect of the waveguide mirror, the pulse width of the mode-locked laser is reduced by a factor of 2.8.

Zhang, Zeyu (ORCID:0000000271576272)↗
NASA NTRS1994

Spectral control of an alexandrite laser for an airborne water-vapor differential absorption lidar system

A narrow-linewidth pulsed alexandrite laser has been greatly modified for improved spectral stability in an aircraft environment, and its operation has been evaluated in the laboratory for making water-vapor differential absorption lidar measurements. An alignment technique is described to achieve the optimum free spectral range ratio for the two etalons inserted in the alexandrite laser cavity, and the sensitivity of this ratio is analyzed. This technique drastically decreases the occurrence of mode hopping, which is commonly observed in a tunable, two-intracavity-etalon laser system. High spectral purity (greater than 99.85%) at 730 nm is demonstrated by the use of a water-vapor absorption line as a notch filter. The effective cross sections of 760-nm oxygen and 730-nm water-vapor absorption lines are measured at different pressures by using this laser, which has a finite linewidth of 0.02 cm(exp -1) (FWHM). It is found that for water-vapor absorption linewidths greater than 0.04 cm(exp -1) (HWHM), or for altitudes below 10 km, the laser line can be considered monochromatic because the measured effective absorption cross section is within 1% of the calculated monochromatic cross section. An analysis of the environmental sensitivity of the two intracavity etalons is presented, and a closed-loop computer control for active stabilization of the two intracavity etalons in the alexandrite laser is described. Using a water-vapor absorption line as a wavelength reference, we measure a long-term frequency drift (approximately 1.5 h) of less than 0.7 pm in the laboratory.

Ponsardin, Patrick↗
NASA NTRS1988

Synchronously pumped mode-locked Ti:Al2O3 lasers

Synchronously pumped mode-locked laser operation in a Ti:Al2O3 ring laser is demonstrated. The laser pump source was a frequency-doubled Nd:YAG laser-amplifier system producing a 60-micron-long macropulse that comprised a wavetrain of mode-locked 70-ps micropulses with a 10-ns spacing (100 MHz). The Ti:Al2O3 laser consisted of a 1-cm-long crystal with faces cut at the Brewster angle and placed in a ring laser cavity configuration with a 2 percent output coupling mirror. The cavity was adjusted for a 5-ns round trip transit time, which was close to half the temporal spacing of the pump pulse. When the crystal was pumped synchronously at 532 nm with a 30-mJ macropulse, which was approximately an order of magnitude above the laser threshold, mode-locked lasing at approximately 200 MHz was obtained. This macropulse pump energy corresponds to an average micropulse pump energy of about 5 microJ at the Ti:Al2O3 crystal face. The mode-locked operation of the Ti:Al2O3 was observed only after several microseconds into the macropulse, indicating a long build-up process over many cavity trips. During this time, relaxation oscillations were observed. When mode locking started, the relaxation oscillation frequency increased by an order of magnitude. Synchronous pumping has been limited to operation with dye lasers and used either a CW or pulsed mode-locked pump source. Recent work has demonstrated CW mode-locked operation of a Ti:Al2O3 laser. The result raises the possibility that pulsed synchronous pumping may be used to obtain significantly narrowed laser pulses in Ti:Al2O3.

Source record↗
NASA NTRS1996

Quantum Noise in Laser Diodes

We have investigated the intensity noise of single mode laser diodes, either free-running or using different types of line narrowing techniques at room temperature. We have measured an intensity squeezing of 1.2 dB with grating-extended cavity lasers and 1.4 dB with injection locked lasers (respectively 1.6 dB and 2.3 dB inferred at the laser output). We have observed that the intensity noise of a free-running nominally single mode laser diode results from a cancellation effect between large anti-correlated fluctuations of the main mode and of weak longitudinal side modes. Reducing the side modes by line narrowing techniques results in intensity squeezing.

Giacobino, E.↗
NASA NTRS2007

Dispersive Elements for Enhanced Laser Gyroscopy and Cavity Stabilization

We analyze the effect of a highly dispersive element placed inside a modulated optical cavity on the frequency and amplitude of the modulation to determine the conditions for cavity self-stabilization and enhanced gyroscopic sensitivity. We find an enhancement in the sensitivity of a laser gyroscope to rotation for normal dispersion, while anomalous dispersion can be used to self-stabilize an optical cavity. Our results indicate that atomic media, even coherent superpositions in multilevel atoms, are of limited use for these applications, because the amplitude and phase filters work against one another, i.e., decreasing the modulation frequency increases its amplitude and vice-versa. On the other hand, for optical resonators the dispersion reversal associated with critical coupling enables the amplitude and phase filters to work together. We find that for over-coupled resonators, the absorption and normal dispersion on-resonance increase the contrast and frequency of the beat-note, respectively, resulting in a substantial enhancement of the gyroscopic response. Under-coupled resonators can be used to stabilize the frequency of a laser cavity, but result in a concomitant increase in amplitude fluctuations. As a more ideal solution we propose the use of a variety of coupled-resonator-induced transparency that is accompanied by anomalous dispersion.

Smith, David D.↗
DOE OSTI2021

High energy (0.8 J) mechanically Q-switched 2.94 μm Er:YAG laser

We report a flashlamp pumped mechanically Q-switched (MQS) 2.94 μm Er:YAG laser based on a spinning mirror with a highest output energy of 805 mJ at a pulse duration of 61 ns and 13 MW of peak power at 1 Hz repetition rate. This record output energy was achieved with the use of 300 mm long MQS Er:YAG laser cavity consisting of a 70% output coupler, 7 × 120 mm AR coated Er(50%):YAG crystal, and 4200 rad/s angular speed of the spinning mirror. The pulse jitter was also measured by using optical triggering and was smaller than 10 ns for 150 ns Q-switched pulses, which could be applicable to many laser applications where precise synchronization of pulses is required.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2020

Low-threshold, single-transverse-mode, 940-nm vertical-cavity surface-emitting laser with a mode filter and half-wavelength cavity

We demonstrate a structure for a vertical-cavity surface-emitting laser (VCSEL) with a mode filter and half-wavelength (λ/2) cavity. The effects of λ/2- and λ-cavities on the threshold current are studied. The thickness and etched diameter of the mode filter are optimised to achieve single-transverse-mode output. The results show that when changing from λ-cavity to λ/2-cavity, the threshold current of the VCSEL decreases by 30.7% (from 0.85 mA to 0.65 mA). In addition, for the mode-filter thickness of 80 nm, and the etched diameter of 2.5 μm, the side mode suppression ratio reaches 90 dB, which meets the requirement of single-transverse-mode output. The VCSELs with the optimised design can overcome many difficulties and have great potential in 3D face recognition. (paper)

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2021

Identification of Brillouin Zones by In-Plane Lasing from Light-Cone Surface Lattice Resonances

Periodic optical structures can control the flow of light, which has facilitated applications in optical fibers, laser cavities, and biochemical sensors. The first Brillouin zone (BZ) in reciprocal space can describe all the electromagnetic fields localized inside a photonic lattice. However, photonic lattices also exhibit radiative losses from light scattering, but the radiated fields are not captured by the first BZ. In a two-dimensional lattice, the in-plane wavevectors of photonic modes are limited by the so-called light cone, which depicts free-photon dispersion relations in the surrounding medium. Here we show that projection of the light cone on extended BZs provides a geometric method to observe radiated electromagnetic fields of photonic lattice modes. We developed a coupled dipole radiation theory to reveal how lattice geometry and dipole orientation affect the angular distributions of the radiated fields. Using dye molecules as local dipole emitters to excite and probe the optical modes, we experimentally identified high-order BZ edges through directional, in-plane lasing emission.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

On quantum-dot lasing at gain peak with linewidth enhancement factor $α$ H = 0

This paper describes an investigation of the linewidth enhancement factor α H in a semiconductor quantum-dot laser. Results are presented for active region parameters and laser configurations important for minimizing α H . In particular, the feasibility of lasing at the gain peak with α H = 0 is explored. The study uses a many-body theory with dephasing effects from carrier scattering treated at the level of quantum-kinetic equations. InAs quantum-dot lasers with different p-modulation doping densities are fabricated and measured to verify the calculated criteria on laser cavity design and epitaxial growth conditions.

42 ENGINEERING↗