Color separation gratings for diverting the unconverted light away from the NIF target

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Most of the glass laser based inertial confinement fusion systems around the world today employ non-linear frequency conversion for converting the 1.053 micrometer light at the fundamental frequency (referred to as 1{omega} light) to either its second harmonic (called 2{omega}) at 527 nm or to its third harmonic (called 3{omega}) at 351 nm. Shorter wavelengths are preferred for laser fusion because of the improved coupling of the laser light to the fusion targets due to reduced fast electron production at shorter wavelengths. The frequency conversion process, however, is only about 60-70% efficient and the residual 30-40% of the energy remains ... continued below

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11 p.

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Dixit, S.N.; Rushford, M.C.; Thomas, I.M.; Herman, S.M.; Britten, J.A.; Shore, B.W. et al. March 11, 1997.

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Description

Most of the glass laser based inertial confinement fusion systems around the world today employ non-linear frequency conversion for converting the 1.053 micrometer light at the fundamental frequency (referred to as 1{omega} light) to either its second harmonic (called 2{omega}) at 527 nm or to its third harmonic (called 3{omega}) at 351 nm. Shorter wavelengths are preferred for laser fusion because of the improved coupling of the laser light to the fusion targets due to reduced fast electron production at shorter wavelengths. The frequency conversion process, however, is only about 60-70% efficient and the residual 30-40% of the energy remains at 1{omega} and 2{omega} frequencies. Color separation gratings (CSGs) offer a versatile approach to reducing and possibly eliminating the unconverted light at the target region. A CSG consists of a three- level lamellar grating designed so that nearly all of the 3{omega} light passes through undiffracted while the residual 1{omega} and 2{omega} energy is diverted into higher diffraction orders. The diffraction angle is determined solely by the grating period. We have demonstrated the concept of using a color separation grating. We fabricated a 345 micrometer period CSG in fused silica using lithographic processes and wet etching. The measured far field indicates that greater than 95% of the incident light is preserved in the 3{omega} zeroth order while less than 5% of unconverted 1{omega} and 2{omega} light is remaining in the zeroth order. We would like to add that diffractive optics fabricated in fused silica by wet etching in hydrofluoric acid should have high damage threshold. Our experience suggests that the damage threshold of the etched substrate is at least as high as the unetched part. 6 refs., 4 figs., 1 tab.

Physical Description

11 p.

Notes

INIS; OSTI as DE97053415

Medium: P; Size: 11 p.

Source

  • 2. annual solid state lasers for applications to inertial confinement fusion (ICF), Paris (France), 22-25 Oct 1996

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  • Other: DE97053415
  • Report No.: UCRL-JC--124512
  • Report No.: CONF-9610225--41
  • Grant Number: W-7405-ENG-48
  • DOI: 10.2172/562816 | External Link
  • Office of Scientific & Technical Information Report Number: 562816
  • Archival Resource Key: ark:/67531/metadc689877

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  • March 11, 1997

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  • Aug. 14, 2015, 8:43 a.m.

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  • April 6, 2017, 7:16 p.m.

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Dixit, S.N.; Rushford, M.C.; Thomas, I.M.; Herman, S.M.; Britten, J.A.; Shore, B.W. et al. Color separation gratings for diverting the unconverted light away from the NIF target, report, March 11, 1997; California. (digital.library.unt.edu/ark:/67531/metadc689877/: accessed August 22, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.