Creating sub angstrom surfaces on planar and spherical substrates

J. Nelson; S. Iles

doi:10.1117/12.2536689

15 November 2019 Creating sub angstrom surfaces on planar and spherical substrates

J. Nelson, S. Iles

Proceedings Volume 11175, Optifab 2019; 1117505 (2019) https://doi.org/10.1117/12.2536689
Event: SPIE Optifab, 2019, Rochester, New York, United States

Abstract

Sub-Angstrom surfaces are frequently specified by customers requiring increased optical and energy efficiency, with most stringent requirements from applications in the UV and from certain high power laser systems. Much research has been performed to understand related surface dynamics, with considerable amounts of information published on precision finishing of optical glass. Many suppliers of low roughness surfaces rely on finishing methods that create subsurface damage through the aggressive removal of material. While the magnitude of this damage can be minimized through the use of progressively finer abrasives, detectable levels of latent structure are still evident. However, finishing processes that merely wipe clean the Beilby layer without disturbing the substrate produce nearly perfect surfaces with little to no subsurface damage. This has been the focus of development efforts at Edmund Optics. By careful management of process variables, extremely smooth surfaces lacking subsurface damage have been demonstrated in fused silica and N-BK7 materials. Applications for optics having these characteristics are found in automotive, defense, medical, and industrial domains. This paper discusses results achieved for producing sub-Angstrom surfaces on fused silica and N-BK7 glass. Surfaces with measured roughness of 0.5Å have consistently been demonstrated on fused silica, with results of around 0.8Å shown for N-BK7. Types of processes useful for achieving these results will be discussed, along with basic metrology methods for producing reliable sub-Angstrom measurements.

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J. Nelson and S. Iles "Creating sub angstrom surfaces on planar and spherical substrates", Proc. SPIE 11175, Optifab 2019, 1117505 (15 November 2019); https://doi.org/10.1117/12.2536689

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