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Title: Design and component specifications for high average power laser optical systems

Abstract

Laser imaging and transport systems are considered in the regime where laser-induced damage and/or thermal distortion have significant design implications. System design and component specifications are discussed and quantified in terms of the net system transport efficiency and phase budget. Optical substrate materials, figure, surface roughness, coatings, and sizing are considered in the context of visible and near-ir optical systems that have been developed at Lawrence Livermore National Laboratory for laser isotope separation applications. In specific examples of general applicability, details of the bulk and/or surface absorption, peak and/or average power damage threshold, coating characteristics and function, substrate properties, or environmental factors will be shown to drive the component size, placement, and shape in high-power systems. To avoid overstressing commercial fabrication capabilities or component design specifications, procedures will be discussed for compensating for aberration buildup, using a few carefully placed adjustable mirrors. By coupling an aggressive measurements program on substrates and coatings to the design effort, an effective technique has been established to project high-power system performance realistically and, in the process, drive technology developments to improve performance or lower cost in large-scale laser optical systems. 13 refs.

Authors:
; ; ;
Publication Date:
Research Org.:
Lawrence Livermore National Lab., CA (USA); Sandia National Labs., Albuquerque, NM (USA)
OSTI Identifier:
6553651
Report Number(s):
UCRL-93452; CONF-860117-15
ON: DE87009136
DOE Contract Number:
W-7405-ENG-48; AC04-76DP00789
Resource Type:
Conference
Resource Relation:
Conference: Los Angeles symposium and exhibition on optical and electro-optical engineering, Los Angeles, CA, USA, 19 Jan 1986; Other Information: Portions of this document are illegible in microfiche products
Country of Publication:
United States
Language:
English
Subject:
47 OTHER INSTRUMENTATION; 07 ISOTOPES AND RADIATION SOURCES; LASER ISOTOPE SEPARATION; OPTICAL SYSTEMS; DESIGN; RADIATION HEATING; COATINGS; DAMAGE; LASERS; ROUGHNESS; SIZE; SPECIFICATIONS; TEMPERATURE EFFECTS; HEATING; ISOTOPE SEPARATION; SEPARATION PROCESSES; SURFACE PROPERTIES; 440300* - Miscellaneous Instruments- (-1989); 070100 - Physical Isotope Separation

Citation Formats

O'Neil, R.W., Sawicki, R.H., Johnson, S.A., and Sweatt, W.C. Design and component specifications for high average power laser optical systems. United States: N. p., 1987. Web.
O'Neil, R.W., Sawicki, R.H., Johnson, S.A., & Sweatt, W.C. Design and component specifications for high average power laser optical systems. United States.
O'Neil, R.W., Sawicki, R.H., Johnson, S.A., and Sweatt, W.C. Thu . "Design and component specifications for high average power laser optical systems". United States. doi:. https://www.osti.gov/servlets/purl/6553651.
@article{osti_6553651,
title = {Design and component specifications for high average power laser optical systems},
author = {O'Neil, R.W. and Sawicki, R.H. and Johnson, S.A. and Sweatt, W.C.},
abstractNote = {Laser imaging and transport systems are considered in the regime where laser-induced damage and/or thermal distortion have significant design implications. System design and component specifications are discussed and quantified in terms of the net system transport efficiency and phase budget. Optical substrate materials, figure, surface roughness, coatings, and sizing are considered in the context of visible and near-ir optical systems that have been developed at Lawrence Livermore National Laboratory for laser isotope separation applications. In specific examples of general applicability, details of the bulk and/or surface absorption, peak and/or average power damage threshold, coating characteristics and function, substrate properties, or environmental factors will be shown to drive the component size, placement, and shape in high-power systems. To avoid overstressing commercial fabrication capabilities or component design specifications, procedures will be discussed for compensating for aberration buildup, using a few carefully placed adjustable mirrors. By coupling an aggressive measurements program on substrates and coatings to the design effort, an effective technique has been established to project high-power system performance realistically and, in the process, drive technology developments to improve performance or lower cost in large-scale laser optical systems. 13 refs.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Thu Jan 01 00:00:00 EST 1987},
month = {Thu Jan 01 00:00:00 EST 1987}
}

Conference:
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  • This book presents the papers given at a conference on lasers. Topics considered at the conference included laser design characteristics, integrated optical materials for laser applications, diamond machined optical components, the fabricating and testing of laser optics, protective coatings, the Nova laser, thin film coatings, and component specifications for high average power laser optical systems.
  • Laser system performance and reliability depends on the related performance and reliability of the optical components which define the cavity and transport subsystems. High-average-power and long transport lengths impose specific requirements on component performance. The complexity of the manufacturing process for optical components requires a high degree of process control and verification. Qualification has proven effective in ensuring confidence in the procurement process for these optical components. Issues related to component reliability have been studied and provide useful information to better understand the long term performance and reliability of the laser system.
  • Laser system performance and reliability depends on the related performance and reliability of the optical components which define the cavity and transport subsystems. High-average-power and long transport lengths impose specific requirements on component performance. The complexity of the manufacturing process for optical components requires a high degree of process control and verification. Qualification has proven effective in ensuring confidence in the procurement process for these optical components. Issues related to component reliability have been studied and provide useful information to better understand the long term performance and reliability of the laser system.
  • This paper describes the use of Fourier techniques to characterize the transmitted and reflected wavefront of optical components. Specifically, a power spectral density, (PSD), approach is used. High power solid-state lasers exhibit non-linear amplification of specific spatial frequencies. Thus, specifications that limit the amplitude of these spatial frequencies are necessary in the design of these systems. Further, NIF optical components have square, rectangular or irregularly shaped apertures with major dimensions up-to 800 mm. Components with non-circular apertures can not be analyzed correctly with Zernicke polynomials since these functions are an orthogonal set for circular apertures only. A more complete andmore » powerful representation of the optical wavefront can be obtained by Fourier analysis in 1 or 2 dimensions. The PSD is obtained from the amplitude of frequency components present in the Fourier spectrum. The shape of a resultant wavefront or the focal spot of a complex multicomponent laser system can be calculated and optimized using PSDs of the individual optical components which comprise the system. Surface roughness can be calculated over a range of spatial scale-lengths by integrating the PSD. Finally, since the optical transfer function (OTF) of the instruments used to measure the wavefront degrades at high spatial frequencies, the PSD of an optical component is underestimated. We can correct for this error by modifying the PSD function to restore high spatial frequency information. The strengths of PSD analysis are leading us to develop optical specifications incorporating this function for the planned National Ignition Facility (NIF).« less
  • The atomic vapor laser isotope separation process uses high-average power lasers that have the commercial potential to enrich uranium for the electric power utilities. The transport of the laser beam through the laser system to the separation chambers requires high performance optical components, most of which have either fused silica or Zerodur as the substrate material. One of the requirements of the optical components is to preserve the wavefront quality of the laser beam that propagate over long distances. Full aperture tests with the high power process lasers and finite element analysis (FEA) have been performed on the transport optics.more » The wavefront distortions of the various sections of the transport path were measured with diagnostic Hartmann sensor packages. The FEA results were derived from an in-house thermal-structural-optical code which is linked to the commercially available CodeV program. In comparing the measured and predicted results, the bulk absorptance of fused silica was estimated to about 50 ppm/cm in the visible wavelength regime. Wavefront distortions are reported on optics made from fused silica and Zerodur substrate materials.« less