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

Haruki Marui; Sora Aikawa; Yuji Umeda; Yusuke Funamoto; Tomosumi Kamimura; Yasunori Tanaka; Ryota Murai; Yoshinori Takahashi; Tsuyoshi Sugita; Masayuki Imanishi; Yusuke Mori; Masashi Yoshimura

doi:10.1117/12.2598554

12 October 2021 Evaluation of surface damage resistance in several polished conditions for SrB4O7 crystal

Haruki Marui, Sora Aikawa, Yuji Umeda, Yusuke Funamoto, Tomosumi Kamimura, Yasunori Tanaka, Ryota Murai, Yoshinori Takahashi, Tsuyoshi Sugita, Masayuki Imanishi, Yusuke Mori, Masashi Yoshimura

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Proceedings Volume 11910, Laser-Induced Damage in Optical Materials 2021; 119101O (2021) https://doi.org/10.1117/12.2598554
Event: SPIE Laser Damage, 2021, Online Only

Conference Poster

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.

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Haruki Marui, Sora Aikawa, Yuji Umeda, Yusuke Funamoto, Tomosumi Kamimura, Yasunori Tanaka, Ryota Murai, Yoshinori Takahashi, Tsuyoshi Sugita, Masayuki Imanishi, Yusuke Mori, and Masashi Yoshimura "Evaluation of surface damage resistance in several polished conditions for SrB4O7 crystal", Proc. SPIE 11910, Laser-Induced Damage in Optical Materials 2021, 119101O (12 October 2021); https://doi.org/10.1117/12.2598554

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