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1.
Opt Express ; 29(24): 39983-39999, 2021 Nov 22.
Artigo em Inglês | MEDLINE | ID: mdl-34809350

RESUMO

High peak and average power lasers with high wall-plug efficiency, like the Big Aperture Thulium (BAT) laser, have garnered tremendous attention in laser technology. To meet the requirements of the BAT laser, we have developed low-dispersion reflection multilayer dielectric (MLD) gratings suitable for compression of high-energy pulses for operations at 2 micron wavelength. We carried out 10000-on-1 damage tests to investigate the fluence damage thresholds of the designed MLD gratings and mirrors, which were found between 100-230 mJ/cm2. An ultrashort pulsed laser (FWHM = 53 fs, λ = 1.9 µm) operating at 500 Hz was used in the serpentine raster scans. The atomic force microscope images of the damage sites show blister formation of the underlying layers at lower fluences but ablation of the grating pillars at higher fluences. We simulated the dynamic electronic excitation in the MLD optics with a finite-difference in the time domain approach in 2D. The simulation results agree well with the LIDT measurements and the observed blister formation. This model is able to evaluate the absolute LIDT of MLD gratings.

2.
Appl Opt ; 60(8): 2288-2303, 2021 Mar 10.
Artigo em Inglês | MEDLINE | ID: mdl-33690328

RESUMO

The advanced radiographic capability (ARC) laser system, part of the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory, is a short-pulse laser capability integrated into the NIF. The ARC is designed to provide adjustable pulse lengths of ∼1-38ps in four independent beamlets, each with energies up to 1 kJ (depending on pulse duration). A detailed model of the ARC lasers has been developed that predicts the time- and space-resolved focal spots on target for each shot. Measurements made to characterize static and dynamic wavefront characteristics of the ARC are important inputs to the code. Modeling has been validated with measurements of the time-integrated focal spot at the target chamber center (TCC) at low power, and the space-integrated pulse duration at high power, using currently available diagnostics. These simulations indicate that each of the four ARC beamlets achieves a peak intensity on target of up to a few 1018W/cm2.

3.
Appl Opt ; 58(31): 8501-8510, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31873335

RESUMO

We report on the design, performance, and qualification of the injection laser system designed to deliver joule-level chirped pulse beamlets arranged in dual rectangular beam formats into two main laser amplifier beamlines of the National Ignition Facility. The system is designed to meet the requirements of the Advanced Radiographic Capability upgrade with features that deliver performance, adjustability, and long-term reliability.

4.
Opt Express ; 24(26): 30015-30023, 2016 Dec 26.
Artigo em Inglês | MEDLINE | ID: mdl-28059386

RESUMO

Laser energy absorption and subsequent heat removal from diffraction gratings in chirped pulse compressors poses a significant challenge in high repetition rate, high peak power laser development. In order to understand the average power limitations, we have modeled the time-resolved thermo-mechanical properties of current and advanced diffraction gratings. We have also developed and demonstrated a technique of actively cooling Petawatt scale, gold compressor gratings to operate at 600W of average power - a 15x increase over the highest average power petawatt laser currently in operation. Combining this technique with low absorption multilayer dielectric gratings developed in our group would enable pulse compressors for petawatt peak power lasers operating at average powers well above 40kW.

5.
Opt Express ; 23(12): 15532-44, 2015 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-26193533

RESUMO

Precise assessment of the high fluence performance of pulse compressor gratings is necessary to determine the safe operational limits of short-pulse high energy lasers. We have measured the picosecond laser damage behavior of multilayer dielectric (MLD) diffraction gratings used in the compression of chirped pulses on the Advanced Radiographic Capability (ARC) kilojoule petawatt laser system at the Lawrence Livermore National Laboratory (LLNL). We present optical damage density measurements of MLD gratings using the raster scan method in order to estimate operational performance. We also report results of R-on-1 tests performed with varying pulse duration (1-30 ps) in air, and clean vacuum. Measurements were also performed in vacuum with controlled exposure to organic contamination to simulate the grating use environment. Results show sparse defects with lower damage resistance which were not detected by small-area damage test methods.

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