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Low scatter and ultra-low reflectivity measured in a fused silica window

Padilla, Cinthia and Fritschel, Peter and Magaña-Sandoval, Fabian and Muniz, Erik and Smith, Joshua R. and Zhang, Liyuan (2014) Low scatter and ultra-low reflectivity measured in a fused silica window. Applied Optics, 53 (7). pp. 1315-1321. ISSN 0003-6935. doi:10.1364/AO.53.001315.

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We investigate the reflectivity and optical scattering characteristics at 1064 nm of an antireflection coated fused silica window of the type being used in the Advanced LIGO gravitational-wave detectors. Reflectivity is measured in the ultra-low range of 5–10 ppm (by vendor) and 14–30 ppm (by us). Using an angle-resolved scatterometer we measure the sample’s bidirectional scattering distribution function (BSDF) and use this to estimate its transmitted and reflected scatter at roughly 20–40 and 1 ppm, respectively, over the range of angles measured. We further inspect the sample’s low backscatter using an imaging scatterometer, measuring an angle resolved BSDF below 10^(−6)  sr^(−1) for large angles (10°–80° from incidence in the plane of the beam). We use the associated images to (partially) isolate scatter from different regions of the sample and find that scattering from the bulk fused silica is on par with backscatter from the antireflection coated optical surfaces. To confirm that the bulk scattering is caused by Rayleigh scattering, we perform a separate experiment measuring the scattering intensity versus input polarization angle. We estimate that 0.9–1.3 ppm of the backscatter can be accounted for by Rayleigh scattering of the bulk fused silica. These results indicate that modern antireflection coatings have low enough scatter to not limit the total backscattering of thick fused silica optics.

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Zhang, Liyuan0000-0002-0898-787X
Additional Information:© 2014 Optical Society of America. Received 5 December 2013; accepted 8 January 2014; posted 24 January 2014 (Doc. ID 202514); published 24 February 2014. This work is supported by National Science Foundation Awards PHY-0970147, PHY-1255650, and PHY-0107417 and by the Research Corporation for Science Advancement Cottrell College Science Award #19839. E. Muniz is supported by (STEM)2, funded by the U.S. Department of Education (Grant# P031C110116-12). The authors thank K.Wanser and G. Childers (CSU Fullerton) for useful discussions about Rayleigh scattering. We thank our colleagues in the LIGO Scientific Collaboration for fruitful discussions about this research and for review of this manuscript.
Funding AgencyGrant Number
Research Corporation for Science Advancement Cottrell College Science Award19839
Department of EducationP031C110116-12
Other Numbering System:
Other Numbering System NameOther Numbering System ID
LIGO Document P1300201
Issue or Number:7
Classification Code:OCIS codes: 290.1483; 120.5820; 310.1210; 110.0110
Record Number:CaltechAUTHORS:20140418-075357276
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Official Citation:Cinthia Padilla, Peter Fritschel, Fabian Magaña-Sandoval, Erik Muniz, Joshua R. Smith, and Liyuan Zhang, "Low scatter and ultra-low reflectivity measured in a fused silica window," Appl. Opt. 53, 1315-1321 (2014)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:45047
Deposited By: Ruth Sustaita
Deposited On:18 Apr 2014 16:14
Last Modified:10 Nov 2021 16:59

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