<title>Recent progress in the quality of KTiOPO4 and Beta-BaB2O4 crystals used for the miniature integrated green SHG laser and 1.5W of cw 266-nm generation</title>

Abstract

ABSTRACT High power deep ultraviolet (UV) radiation has attracted much attention in areas of photo-lithography, micro fabrication and material processing as well as ultra high density optical disk mastering. We report progress in quality of 3-BaB2O4 (BBO) which is essential in obtaining 1.5W ofcw UV generation from the BBO resonant ring cavity out of 3W of green input power from a diodepumped Nd:YAG laser. Progress in KTiOPO4 (KTP) and its potential applications are also reviewed. 24-BaB2O4 f-BaB2O4 (BBO) is a well-known nonlinear material useful for second harmonic generation (SHG) and optical parametric oscillation (OPO). To grow the crystal, top-seeded solution growth has been widely used. However, the crystal quality is characterized by a lot of point defects due to flux inclusions.High-purity BBO growth from a BaB2O4 melt by Czochralski method was reported by Itoh et a11. We obtained typically 30 mm-diameter, 30 mm-thick BBO crystal by the direct-melt-growth method asshown in Fig.1. The absorption edge of the BBO is observed at 190 nm. (Fig.2) Considering theFresnel reflection loss, the crystal exhibits good transparency at longer than 200 nm. Figures 3a, 3b