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Title: Gratings for High-Energy Petawatt Lasers

Abstract

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.

Authors:
; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
887293
Report Number(s):
UCRL-CONF-217007
TRN: US200618%%57
DOE Contract Number:
W-7405-ENG-48
Resource Type:
Conference
Resource Relation:
Conference: Presented at: SPIE Boulder Damage Symposium XXXVII, Boulder, CO, United States, Sep 19 - Sep 23, 2005
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 42 ENGINEERING; APERTURES; DESIGN; DIELECTRIC MATERIALS; DIFFRACTION GRATINGS; FABRICATION; LASERS; PETAWATT POWER RANGE; PROCESSING; REFLECTION

Citation Formats

Nguyen, H T, Britten, J A, Carlson, T C, Nissen, J D, Summers, L J, Hoaglan, C R, Aasen, M D, Peterson, J E, and Jovanovic, I. Gratings for High-Energy Petawatt Lasers. United States: N. p., 2005. Web.
Nguyen, H T, Britten, J A, Carlson, T C, Nissen, J D, Summers, L J, Hoaglan, C R, Aasen, M D, Peterson, J E, & Jovanovic, I. Gratings for High-Energy Petawatt Lasers. United States.
Nguyen, H T, Britten, J A, Carlson, T C, Nissen, J D, Summers, L J, Hoaglan, C R, Aasen, M D, Peterson, J E, and Jovanovic, I. Tue . "Gratings for High-Energy Petawatt Lasers". United States. doi:. https://www.osti.gov/servlets/purl/887293.
@article{osti_887293,
title = {Gratings for High-Energy Petawatt Lasers},
author = {Nguyen, H T and Britten, J A and Carlson, T C and Nissen, J D and Summers, L J and Hoaglan, C R and Aasen, M D and Peterson, J E and Jovanovic, I},
abstractNote = {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.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue Nov 08 00:00:00 EST 2005},
month = {Tue Nov 08 00:00:00 EST 2005}
}

Conference:
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  • At the time of this writing, we have manufactured and delivered more than 25 multilayer dielectric diffraction gratings from 470-800 mm in long aperture for pulse compression on Petawatt-class,1-micron laser systems being built at government and university facilities in the U.S and elsewhere. We present statistics of diffraction efficiency and its spatial uniformity, diffracted wavefront, and laser damage results on witness gratings. We also discuss yield, failure modes, and manufacturing improvements necessary to improve upon the current state of the art.
  • We report on the construction, commissioning and characterization of a reactive ion mill capable of submicron pattern transfer into hard dielectric materials on optical substrates as large as 2 x 1 m, for application to fielding high-Energy Petawatt (HEPW) capability on the National Ignition Facility (NIF) laser. Scanning Faraday cup current probe measurements have been used to optimize the ion beam spatial uniformity. Using process parameters obtained from this study, an 81 cm round optic was etched, and etch depth uniformity of {+-} 3.1% absolute was demonstrated. Uniformity of multilayer dielectric gratings of designs employing an etch-stop layer will havemore » etch depth uniformities of approximately a factor of 10 better than this. We also report on initial results of etching multilayer dielectric gratings.« less
  • The next generation of high-energy petawatt (HEPW)-class lasers will utilize multilayer dielectric diffraction gratings for pulse compression due to their high efficiency and high damage threshold for picosecond pulses. We have developed a short-pulse damage test station for accurate determination of the damage threshold of the optics used on future HEPW lasers. The design and performance of the damage test laser source, based on a highly stable, high-beam-quality optical parametric chirped-pulse amplifier, is presented. Our short-pulse damage measurement methodology and results are discussed. The damage initiation is attributed to multiphoton-induced avalanche ionization, strongly dependent on the electric field enhancement inmore » the grating groove structure and surface defects. Measurement results of the dependence of damage threshold on the pulse width, angular dependence of damage threshold of diffraction gratings, and an investigation of short-pulse conditioning effects are presented. We report record >4 J/cm{sup 2} right section surface damage thresholds obtained on multilayer dielectric diffraction gratings at 76.5 incidence angles for 10-ps pulses.« less
  • In this paper we discuss recent work on the development of high damage threshold, high efficiency MLD (multilayer dielectric) diffraction gratings for use in high energy, petawatt laser systems. This effort involves a close integration between modeling, fabrication, and testing. The modeling work is used to identify grating designs that satisfy the constraints of high efficiency (>94%) and low field enhancement which is a necessary condition for high damage threshold. Subscale MLD gratings for test are being fabricated in an advanced ion-etch machine we have recently built. The testing effort is being conducted in a dedicated laboratory. The laser beammore » used to test the samples is based on an OPCPA (optical parametric chirped-pulse amplifier) and a compressor that can provide pulse energies up to 50mJ with pulse lengths variable from 0.3-20 ps. This test station is equipped with diagnostics to fully characterize both the spatial and temporal characteristics of the test beam at the plane of the sample. Initial results have demonstrated a dependence of damage threshold on incident angle that is in good agreement with the field enhancement calculations. We have demonstrated a grating design with a damage threshold of 3J/cm{sup 2} and are investigating manufacturability and reproducibility issues as well.« less
  • We have measured the characteristics of high energy K{alpha} sources created with the Vulcan Petawatt laser at RAL and the JanUSP laser at LLNL. High energy x-ray backlighters will be essential for radiographing High-Energy-Density Experimental Science (HEDES) targets for NIF projects especially to probe implosions and high areal density planar samples. Hard K{alpha} x-ray photons are created through relativistic electron plasma interactions in the target material after irradiation by short pulse high intensity lasers. For our Vulcan experiment, we employed a CsI scintillator/CCD camera for imaging and a CCD camera for single photon counting. We measured the Ag K{alpha} sourcemore » (22 keV) size using a pinhole array and the K{alpha} flux using a single photon counting method. We also radiographed a high Z target using the high energy broadband x-rays generated from these short pulse lasers. This paper will present results from these experiments.« less