Abstract

Tunable CW single-frequency lasers are well-suited to applications in high resolution spectroscopy and metrology. Ultraviolet (UV) sources based on second harmonic generation (SHG) of Ti:sapphire or diode lasers are of particular interest since alternative UV tunable laser are often inefficient and impractical. For a given infrared laser, the second harmonic generation efficiency is optimised by choosing a nonlinear material with high d_eff, capable of non-critical phase-matching (NCPM) to maximize acceptance angle and minimize walk-off effects. At visible wavelengths NCPM can be achieved in KNbO₃ and LBO, but below 400 nm the candidate nonlinear materials BBO, LBO, and LIO₃ must be critically phase-matched. The emergence of periodically poled lithium niobate (PPLN) offers the potential for NCPM SHG with much higher deff values. SHG for blue¹ and green generation has been demonstrated in PPLN, and we recently obtained efficient SHG of a pulsed 800 nm laser². Here we report efficient CW UV generation close to the absorption edge in PPLN by intracavity SHG of a Ti:sapphire laser.

© 2000 IEEE