SEDL / STP / STP1028-EB / STP18562S

Highly Damage Resistant Anti-reflection Coating on the Chemically Etched Surface for High Power Lasers

Yoshida, K
Institute of Laser Engineering Osaka University, Osaka,

Yoshida, H
Institute of Laser Engineering Osaka University, Osaka,

Kato, Y
Institute of Laser Engineering Osaka University, Osaka,

Yamanaka, C
Institute of Laser Engineering Osaka University, Osaka,

Ohtani, M
Institute of Laser Engineering Osaka University, Osaka,

Pages: 1    Published: Jan 1988

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Abstract

When the surface of BK-7 glass is conventionally polished by CeO² as polishing compound, the polishing compound is buried into the substrate. The buried compound can not be removed by standard optical cleaning techniques. Therefore, when the polished surface is anti-reflection (AR) coated and exposed to the focussed laser beam, the surface ionization occurs due to absorption at the isolated sites, leading to laser induced damages in the AR coating.

In order to improve the damage threshold, we have prepared the BK-7 substrate which was chemically etched after polishing. The damage threshold of the AR coating on the etched surface showed 1.5∼2 times improvement compared with that of un-etched surface, at the laser wavelength of 1.06 &m and 1 ns pulse width. Due to the special etching technique, the surface roughness of the etched surface was 10∼15 Årms, which was close to the surface roughness before etching (7∼12 Årms).