Conference 11910 > Paper 11910-54
Paper 11910-54

Evaluation of surface damage resistance in several polished conditions for SrB4O7 crystal

On demand starting 12 October 2021

Abstract

The developments of ultra-high purity material which resist the damage by DUV laser are strongly required. According to the general mechanism of laser-induced damage, some kinds of defects and contaminations on the optical material are very important factors for DUV laser-induced damage. The borate crystal SrB4O7 (SBO) was reported to be a nonlinear optical material with a wide transparency down to 130 nm. In this study, we grew a high-quality SBO single crystal and measured the surface DUV laser-induced damage threshold (LIDT) in several polished conditions. The SBO crystals grown over 13 days was 60 x 6 x 30 mm3 (a x b x c) without cracks or other defects. Two (020) plates were cut from the SBO crystal, and the both faces of the plates were optically polished. After that, we introduced catalyst-referred etching (CARE) to the one plate in order to atomically produce flat and damage-free SBO surfaces. As a result of the CARE treatment at a removal rate of 364 nm/h, the surface condition changed drastically, and a linear step-and-terrace structure was grew with a step height of 0.2 nm. The surface LIDT in several polished conditions were measured with a 1-on-1 method at 266 nm (5 ns pulse width). The polarization direction was parallel to the c-axis of the (020) sample. Synthetic silica was also evaluated for comparison. The surface LIDT (17.3 J/cm2) of SBO after optical polishing is 4.3 times that of synthetic silica (4.0 J/cm2). In addition, the surface LIDT (24.1 J/cm2) of CARE-treated SBO is 6.0 times that of synthetic silica. This suggests that CARE-treated SBO crystals are a promising material for optical components in high-power DUV laser systems.

Presenter

Osaka Institute of Technology (Japan)
Presenter/Author
Osaka Institute of Technology (Japan)
Author
Sora Aikawa
Osaka Institute of Technology (Japan)
Author
Osaka Institute of Technology (Japan)
Author
Osaka Institute of Technology (Japan)
Author
Osaka Institute of Technology (Japan)
Author
Yasunori Tanaka
Osaka Univ. (Japan)
Author
Osaka Univ. (Japan)
Author
Yoshinori Takahashi
Osaka Univ. (Japan)
Author
Nikon Corp. (Japan)
Author
Osaka Univ. (Japan)
Author
Osaka Univ. (Japan)
Author
Masashi Yoshimura
Osaka Univ. (Japan)