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Title: VUV and XUV reflectance of optically coated mirrors for selection of high harmonics

Abstract

We report the reflectance, ~1° from normal incidence, of six different mirrors as a function of photon energy, using monochromatic vacuum ultraviolet (VUV) and extreme ultraviolet (XUV) radiation with energies between 7.5 eV and 24.5 eV. The mirrors examined included both single and multilayer optical coatings, as well as an uncoated substrate. Furthermore, we discuss the performance of each mirror, paying particular attention to the potential application of suppression and selection of high-order harmonics of a Ti:sapphire laser.

Authors:
 [1];  [2];  [3];  [1];  [4];  [2];  [3];  [3];  [3];  [3]
  1. Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States)
  3. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  4. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Davis, CA (United States)
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Workforce Development for Teachers and Scientists (WDTS) (SC-27)
OSTI Identifier:
1313072
Grant/Contract Number:
AC02-05CH11231
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Optics Express
Additional Journal Information:
Journal Volume: 24; Journal Issue: 16; Journal ID: ISSN 1094-4087
Publisher:
Optical Society of America (OSA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ultraviolet vacuum; ultraviolet extreme; optical design and fabrication; mirrors; multilayers; interference coatings

Citation Formats

Larsen, K. A., Cryan, J. P., Shivaram, N., Champenois, E. G., Wright, T. W., Ray, D., Kostko, O., Ahmed, M., Belkacem, A., and Slaughter, D. S. VUV and XUV reflectance of optically coated mirrors for selection of high harmonics. United States: N. p., 2016. Web. doi:10.1364/OE.24.018209.
Larsen, K. A., Cryan, J. P., Shivaram, N., Champenois, E. G., Wright, T. W., Ray, D., Kostko, O., Ahmed, M., Belkacem, A., & Slaughter, D. S. VUV and XUV reflectance of optically coated mirrors for selection of high harmonics. United States. doi:10.1364/OE.24.018209.
Larsen, K. A., Cryan, J. P., Shivaram, N., Champenois, E. G., Wright, T. W., Ray, D., Kostko, O., Ahmed, M., Belkacem, A., and Slaughter, D. S. 2016. "VUV and XUV reflectance of optically coated mirrors for selection of high harmonics". United States. doi:10.1364/OE.24.018209. https://www.osti.gov/servlets/purl/1313072.
@article{osti_1313072,
title = {VUV and XUV reflectance of optically coated mirrors for selection of high harmonics},
author = {Larsen, K. A. and Cryan, J. P. and Shivaram, N. and Champenois, E. G. and Wright, T. W. and Ray, D. and Kostko, O. and Ahmed, M. and Belkacem, A. and Slaughter, D. S.},
abstractNote = {We report the reflectance, ~1° from normal incidence, of six different mirrors as a function of photon energy, using monochromatic vacuum ultraviolet (VUV) and extreme ultraviolet (XUV) radiation with energies between 7.5 eV and 24.5 eV. The mirrors examined included both single and multilayer optical coatings, as well as an uncoated substrate. Furthermore, we discuss the performance of each mirror, paying particular attention to the potential application of suppression and selection of high-order harmonics of a Ti:sapphire laser.},
doi = {10.1364/OE.24.018209},
journal = {Optics Express},
number = 16,
volume = 24,
place = {United States},
year = 2016,
month = 8
}

Journal Article:
Free Publicly Available Full Text
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  • We report the reflectance, ~1° from normal incidence, of six different mirrors as a function of photon energy, using monochromatic vacuum ultraviolet (VUV) and extreme ultraviolet (XUV) radiation with energies between 7.5 eV and 24.5 eV. The mirrors examined included both single and multilayer optical coatings, as well as an uncoated substrate. We discuss the performance of each mirror, paying particular attention to the potential application of suppression and selection of high-order harmonics of a Ti:sapphire laser.
  • This paper reports methods developed to maximize the overall reflectance second-surface silvered glass. The reflectance at shorter wavelengths is increased with the aid of a dielectric enhancing layer between the silver and the glass, while at longer wavelengths it is enhanced by use of glass with negligible iron content. The calculated enhancement of reflectance, compared to unenhanced silver on standard low-iron float glass, corresponds to a 4.4% increase in reflectance averaged across the full solar spectrum, appropriate for CSP, and 2.7% for CPV systems using triple junction cells. An experimental reflector incorporating these improvements, of drawn crown glass and amore » silvered second-surface with dielectric boost, was measured at NREL to have 95.4% solar weighted reflectance. For comparison, non-enhanced, wetsilvered reflectors of the same 4 mm thickness show reflectance ranging from 91.6 - 94.6%, depending on iron content. A potential drawback of using iron-free drawn glass is reduced concentration in high concentration systems because of the inherent surface errors. This effect is largely mitigated for glass shaped by slumping into a concave mold, rather than by bending.« less
  • Molybdenum--silicon multilayer (ML) x-ray mirrors have been fabricated using a direct-current planar magnetron sputtering system. The ML structure has been characterized using x-ray diffraction and high-resolution electron microscopy, and the normal incidence x-ray reflectivity has been measured using synchrotron radiation. A striking dependence of the ML morphology on the sputtering gas pressure is observed, exhibiting a transition from layer growth at lower pressures to columnar growth at higher pressures. Correspondingly, the normal incidence x-ray reflectivity is found to decrease strongly with increasing gas pressure. By depositing Mo--Si ML at low sputtering gas pressures we have achieved a normal incidence reflectivitymore » as high as 61% at 132 A.« less
  • We have developed a photoacoustic technique to calculate high mirror reflectance using absorptance, transmittance, and scattering measurements.
  • Cr-Ti multilayers with ultrashort periods of 1.39-2.04nm have been grown for the first time as highly reflective, soft-x-ray multilayer, near-normal incidence mirrors for transition radiation and Cherenkov radiation x-ray sources based on the Ti-2p absorption edge at E=452eV (lambda=2.74nm). Hard, as well as soft, x-ay reflectivity and transmission electron microscopy were used to characterize the nanostructure of the mirrors. To achieve minimal accumulated roughness, improved interface flatness, and to avoid intermixing at the interfaces, each individual layer was engineered by use of a two-stage ion assistance process during magnetron sputter deposition: The first 0.3nm of each Ti and Cr layermore » was grown without ion assistance, and the remaining 0.39-0.72nm of the layers were grown with high ion-neutral flux ratios Phi(PhiTi=3.3,PhiCr=2.2) and a low energy Eion (ETi=23.7andECr=21.2), ion assistance. A maximum soft-x-ray reflectivity of R=2.1% at near-normal incidence ({approx}78.8 deg.) was achieved for a multilayer mirror containing 100 bilayers with a modulation period of 1.379nm and a layer thickness ratio of Gamma=0.5. For a polarizing multilayer mirror with 150 bilayers designed for operation at the Brewster angle, 45 deg., an extinction ratio, Rs/Rp, of 266 was achieved with an absolute reflectivity of R=4.3%.« less