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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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A high power pulsed dye laser was used to optically excite high pressure cesium-xenon mixtures and the resulting measurements are presented. A microwave discharge in rubidium at relatively high xenon pressure was achieved. Preliminary studies of cadium-rare gas mixtures are discussed and a detailed description of the entire experimental apparatus is given.
Nanophotonic materials enable unprecedented control of light-matter interactions, including the ability to dynamically steer or shape wavefronts. Consequently, nanophotonic systems such as metasurfaces have been touted as promising candidates for free-space optical communications, directed energy and additive manufacturing, which currently rely on slow mechanical scanners or electro-optical components for beam steering and shaping. However, such applications necessitate the ability to support high laser irradiances (> kW/cm 2 ) and systematic studies on the high-power laser damage performance of nanophotonic materials and designs are sparse. Here, we experimentally investigate the pulsed laser-induced damage performance (at λ ∼ 1 µm) of model nanophotonic thin films including gold, indium tin oxide, and refractory materials such as titanium nitride and titanium oxynitride. We also model the spatio-thermal dissipation dynamics upon single-pulse illumination by anchoring experimental laser damage thresholds. Our findings show that gold exhibits the best laser damage resistance, but we argue that alternative materials such as transparent conducting oxides could be optimized to balance the tradeoff between damage resistance and optical tunability, which is critical for the design of thermally robust nanophotonic systems. We also discuss damage mitigation and ruggedization strategies for future device-scale studies and applications requiring high power beam manipulation.
High power gas laser concepts are discussed with emphasis on the role that fluid mechanics has played in their development. Consideration is given to three types of systems: gasdynamic lasers, HF supersonic diffusion lasers, and electric discharge lasers. Flow effects and aerodynamic windows in such lasers are briefly described. Future directions of research are outlined.
Lasers with high peak power pulses are commonly used in spaceflight missions for a wide range of applications, from LIDAR systems to optical communications. Due to the high optical power needed, the laser has to be located on the exterior of the satellite or coupled through a series of free space optics. This presents challenges for thermal management, radiation resistance, and mechanical design. Future applications will require multiple lasers located close together, which further complicates the design. Coupling the laser energy into a fiber optic cable allows the laser to be relocated to a more favorable position on the spacecraft. Typical fiber optic termination procedures are not sufficient for injection of these high-power laser pulses without catastrophic damage to the fiber endface. In the current study, we will review the causes of fiber damage during high-power injection and discuss our new manufacturing procedures that overcome these issues to permit fiber use with high reliability in these applications. We will also discuss the proper methods for launching the laser pulses into the fiber to avoid damage and how this is being implemented for current spaceflight missions.
The next generation of high-power lasers enables repetition of experiments at orders of magnitude higher frequency than what was possible using the prior generation. Facilities requiring human intervention between laser repetitions need to adapt in order to keep pace with the new laser technology. A distributed networked control system can enable laboratory-wide automation and feedback control loops. These higher-repetition-rate experiments will create enormous quantities of data. A consistent approach to managing data can increase data accessibility, reduce repetitive data-software development and mitigate poorly organized metadata. An opportunity arises to share knowledge of improvements to control and data infrastructure currently being undertaken. We compare platforms and approaches to state-of-the-art control systems and data management at high-power laser facilities, and we illustrate these topics with case studies from our community
We describe a research program to develop high quality plasma mirrors for use with high repetition rate, high power laser facilities to greatly facilitate experiments in high energy density physics, particularly when using solid density targets. A system delivering ultrathin, free standing liquid crystal films that could handle PW class laser pulses was developed that preserved the laser beam image quality and improved pulse contrast by over two orders of magnitude. The pulse contrast improvement was measured using a high dynamic range cross-correlation. The system operated at a repetition rate of several PMs formed in situ per minute. Extension to 1 Hz repetition rates should be possible. As a practical application, a PM system was used to separate laser accelerated electrons from the ultrashort pulse drive laser so that the electron beam emittance could be directly measured. The 20 nm thick PMs did not contribute significantly to emittance degradation. It was also demonstrated that the films could operate in the difficult plasma and laser environment present for GeV laser based electron acceleration. PM operation is still not well understood and much work with PMs is done empirically. Accordingly, we also demonstrated a particle-in-cell based simulation technique that would model PM operation, tracking the PM operation from cold, neutral atoms to a hot dense plasma by accounting for multiphoton ionization, plasma collisionality, and the dynamically changing index of refraction. Simulations in 3D were compared to a 2D based approach that was comparable. Finally, we developed a simpler model that can predict the intensity at which a plasma mirror will have its peak reflectivity.
The design and operation of high-power lasers for industrial applications are discussed in reviews and reports. Topics addressed include the status of optical technology in the Netherlands, laser design, the deposition of optical energy, laser diagnostics, nonmetal processing, and energy coupling and plasma formation. Consideration is given to laser-induced damage to materials, fluid and gas flow dynamics, metal processing, and manufacturing. Graphs, diagrams, micrographs, and photographs are provided.
A high-power, continuous-wave laser was designed for use in power transmission and energy-collecting systems, and for producing incoherent light for pumping a laser material. The laser has a high repetitive pulsing rate per unit time, resulting in a high-power density beam. The laser is composed of xenon flash tubes powered by fast-charging capacitors flashed in succession by a high-speed motor connected to an automobile-type distributor.
Abstract High-power lasers are vital for particle acceleration, imaging, fusion and materials processing, requiring precise control and high-energy delivery. Laser plasma accelerators (LPAs) demand laser positional stability at focus to ensure consistent electron beams in applications such as X-ray free-electron lasers and high-energy colliders. Achieving this stability is especially challenging for the low-repetition-rate lasers in current LPAs. We present a machine learning method that predicts and corrects laser pointing instabilities in real-time using a high-frequency pilot beam. By preemptively adjusting a correction mirror, this approach overcomes traditional feedback limits. Demonstrated on the BELLA petawatt laser operating at the terawatt level (30 mJ amplification), our method achieved root mean square pointing stabilization of 0.34 and 0.59 $\unicode{x3bc} \mathrm{rad}$ in the x and y directions, reducing jitter by 65% and 47%, respectively. This is the first successful application of predictive control for shot-to-shot stabilization in low-repetition-rate laser systems, paving the way for full-energy petawatt lasers and transformative advances across science, industry and security.
We report on a seventh annual workshop in a series focused on science realized by the combination of hard X-ray free electron lasers with high power optical lasers, hosted at the SLAC National Accelerator Laboratory in Menlo Park, CA. Members from the user community of the Matter in Extreme Conditions (MEC) endstation of the Linac Coherent Light Source (LCLS) and other scientists met with local scientists to discuss developments at LCLS and MEC and related facilities, including experimental results and future plans.
High-power semiconductor laser diodes selected for use in the NASA space laser communications experiments are discussed. The diode selection rationale is reviewed, and the laser structure is shown. The theory and design of the third mirror lasers used in the experiments are addressed.
Abstract Birefringent materials—which are highly needed in high power laser systems—may be limited in usage due to the laser‐induced damage threshold of traditional birefringent materials. This work reports here on all‐glass metasurfaces, fabricated by angled etching through sacrificial metal nanoparticle (NP) etching masks, for generation of effective birefringence in the formed layer. As a result, a fused silica metasurface, monolithic to the underlying substrate, is demonstrated to exhibit a birefringence of 6.57° under 375 nm illumination. Full‐wave analysis shows a good agreement with the measurement and presents potential paths forward to increasing the effective metasurface birefringence. This is the first demonstration, to the best of knowledge, of an etching technique to obtain the resulting tilted pillar‐like nanofeatures. The anisotropy of the metasurface nanoelements along the two window in‐plane major axes presents different effective paths for the two polarizations and thus generates birefringence in a nonbirefringent material. Additionally, the imparted anisotropy lends itself to manipulation of physical properties of the surface as well, with metasurface feature orientation suppressing water flow along one principal axis and giving rise to water flow steering capabilities.
The overall objectives of the NASA High Power Laser Program are reviewed along with their structure and center responsibilities. Present and future funding, laser power transmission in space, selected program highlights, the research and technology schedule, and the expected pace of the program are briefly considered.
Here, Biermann battery magnetic field generation driven by high power laser–solid interactions is explored in experiments performed with the OMEGA EP laser system. Proton deflectometry captures changes to the strength, spatial profile, and temporal dynamics of the self-generated magnetic fields as the target material or laser intensity is varied. Measurements of the magnetic flux during the interaction are used to help validate extended magnetohydrodynamic (MHD) simulations. Results suggest that kinetic effects cause suppression of the Biermann battery mechanism in laser–plasma interactions relevant to both direct and indirect-drive inertial confinement fusion. Experiments also find that more magnetic flux is generated as the target atomic number is increased, which is counter to a standard MHD understanding.
The use of computer generated, reflection holograms in conjunction with high power lasers for precision machining of metals and ceramics was investigated. The Reflection holograms which were developed and made to work at both optical wavelength (He-Ne, 6328 A) and infrared (CO2, 10.6) meet the primary practical requirement of ruggedness and are relatively economical and simple to fabricate. The technology is sufficiently advanced now so that reflection holography could indeed be used as a practical manufacturing device in certain applications requiring low power densities. However, the present holograms are energy inefficient and much of the laser power is lost in the zero order spot and higher diffraction orders. Improvements of laser machining over conventional methods are discussed and addition applications are listed. Possible uses in the electronics industry include drilling holes in printed circuit boards making soldered connections, and resistor trimming.
High-power laser diode arrays (LDAs) are used for a variety of space-based remote sensor laser programs as an energy source for diode-pumped solid-state lasers. LDAs have been flown on NASA missions including MOLA, GLAS and MLA and have continued to be viewed as an important part of the laser-based instrument component suite. There are currently no military or NASA-grade, -specified, or - qualified LDAs available for "off-the-shelf" use by NASA programs. There has also been no prior attempt to define a standard screening and qualification test flow for LDAs for space applications. Initial reliability studies have also produced good results from an optical performance and stability standpoint. Usage experience has shown, howeve that the current designs being offered may be susceptible to catastrophic failures due to their physical construction (packaging) combined with the electro-optical operational modes and the environmental factors of space application. design combined with operational mode was at the root of the failures which have greatly reduced the functionality of the GLAS instrument. The continued need for LDAs for laser-based science instruments and past catastrophic failures of this part type demand examination of LDAs in a manner which enables NASA to select, buy, validate and apply them in a manner which poses as little risk to the success of the mission as possible.
A review of recent developments in high power, carbon dixoide laser welding is presented. Deep penetration welding in stainless steel to 0.5-in. thick, high speed welding in thin gage rimmed steel and gas shielded welding in Ti-6Al-4V alloy are described. The effects of laser power, power density, focusing optics, gas-shielding techniques, material properties and weld speed on weld quality and penetration are discussed. It is shown that laser welding performance in thin materials is comparable to that of electron beams. It is further shown that high quality welds, as evidenced by NDT, mechanical and metal-lographic tests, can be achieved. The potential of the laser for industrial welding applications is indicated.
Lasers pumped by solar heated blackbody cavities have potential for multimegawatt power beaming in space. There are two basic types of blackbody lasers; cavity pumped and transfer system. The transfer system is judged to be more readily scalable to high power. In this system, either N2 or CO is heated by the blackbody cavity then transferred into the laser cavity where CO2 is injected. The N2-CO2 system was demonstrated, but probably has lower efficiency than the CO-CO system. The characteristics of potential transfer laser systems are outlined.