Double-pass pumped extracavity optical parametric oscillator with passive optical feedback suppression

Abstract

We demonstrate a simple way of building a compact eye-safe laser source based on a double-pass pumped extracavity optical parametric oscillator (EOPO) without an optical Faraday isolator. A Nd:KGW pump laser (PL) and the KTP EOPO located close to the PL are designed with stable cavities, while the 100% end system mirrors form an unstable cavity with sufficiently high threshold at 1067 nm. At the 6.6 J pump of the Nd:KGW laser, the EOPO output energy obtained at 1577 nm is 14.7 mJ, corresponding to the conversion efficiency of 33% with respect to the fundamental. The pulse width is 7 ns and the output beam divergence is 3 times diffraction limit.

Theoretical study on broadband second harmonic generation in periodically and aperiodically poled KTP

“…Furthermore, the step between two adjacent sections of chirped crystals is usually a nanometer scale, which is restricted by technical conditions in the fabrication process. On the other hand, the KTP crystal is becoming an important nonlinear material with the development of QPM technology; due to its large nonlinearity, relatively high damage threshold, good power-handing capability and low susceptibility to photorefractive damage [10,11]. Moreover, poled KTP crystals can be easily fabricated by means of electric-field poling, owing to their low coercive field and quasi-1D structure [12].…”