The advent of high energy, high peak power laser systems through chirped pulse amplification (CPA) in broadband solid-state gain media has opened new avenues into High Energy Density, High Field and Material Science research. There are ongoing efforts at numerous institutions in Europe, USA, and China that are striving to achieve output powers up to 200 PW. One main limitation of total laser energy output is the damage threshold and physical size of diffraction gratings. For the 10 PW (1.5 kJ, 150 fs) ELI-Beamline L4 Aton laser, we have developed a new class of meter-sized, multilayer dielectric (MLD) gratings based a low-dispersion design of 1136 lines/mm for a Littrow out-of-plane compressor design operating at 1060 nm. This new class of MLD gratings allows for approximately 4X more total energy on grating compared to the present state of the art. Fabrication of a 850 mm wide x 700 mm tall grating resulted in 98.7% efficiency with 0.3% uniformity at 1060 nm.
We present experimental results that show how diode-pumped Tm:YLF can be used to develop the next generation of lasers with high peak and high average power. We demonstrate the production of broad bandwidth, λ≈ 1.9 μm wavelength, high energy pulses with up to 1.6 J output energy and subsequent compression to sub-300 fs duration. This was achieved using a single 8-pass amplifier to boost stretched approximately 50 μJ pulses to the Joule-level. Furthermore, we show the average power capability of this material in a helium gas-cooled amplifier head, achieving a heat removal rate almost ten times higher than the state-of-the-art, surpassing 20 W/cm2. These demonstrations illustrate the capabilities of directly diode-pumped Tm:YLF to support TW to PW-class lasers at kW average power.
We investigate the laser damage resistance of multilayer dielectric (MLD) diffraction gratings used in the pulse compressors for high energy, high peak power laser systems such as the Advanced Radiographic Capability (ARC) Petawatt laser on the National Ignition Facility (NIF). Our study includes measurements of damage threshold and damage density (ρ(Φ)) with picosecond laser pulses at 1053 nm under relevant operational conditions. Initial results indicate that sparse defects present on the optic surface from the manufacturing processes are responsible for damage initiation at laser fluences below the damage threshold indicated by the standard R-on-1 test methods, as is the case for laser damage with nanosecond pulse durations. As such, this study supports the development of damage density measurements for more accurate predictions on the damage performance of large area optics.
To enable high-energy petawatt laser operation we have developed the processing methods and tooling that produced both the world's largest multilayer dielectric reflection grating and the world's highest laser damage resistant gratings. We have successfully delivered the first ever 80 cm aperture multilayer dielectric grating to LLNL's Titan Intense Short Pulse Laser Facility. We report on the design, fabrication and characterization of multilayer dielectric diffraction gratings.
Edge emitting LEDs(EELEDs) can be used to generate full color scanned displays. Conventional LEDs lack the high speed modulation characteristics and radiance required for this application. InGaN-based EELEDs can be used for blue and green sources, and InGaP-based EELEDs for red sources. These semiconductor light sources are processed and packaged similar to laser diodes, but the primary source of output radiation is spontaneous emission. In this paper we describe the optical farfield characteristics of EELEDs, as well as their near-field and imaging properties. Comparisons are made to laser diode (LD) sources. The near- fields and far-fields of these devices have characteristics in common with both laser diode and conventional surface emitting LEDs. Smaller emitter dimensions produce laser- diode-like diffraction limited behavior, while larger emitter dimensions supporting higher order optical modes, produce broad far-field intensity distributions, and geometrical imaging characteristics. Partly due to the absence of optical gain, the wall plug efficiencies, and optical power levels, are also much lower than laser diodes.
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