title: Relaxed damage threshold intensity conditions and nonlinear increase in the conversion efficiency of an optical parametric oscillator using a bi-directional pump geometry.
abstract: A novel bi-directional pump geometry that nonlinearly increases the nonlinear optical conversion efficiency of a synchronously pumped optical parametric oscillator (OPO) is reported. This bi-directional pumping method synchronizes the circulating signal pulse with two counter-propagating pump pulses within a linear OPO resonator. Through this pump scheme, an increase in nonlinear optical conversion efficiency of 22% was achieved at the signal wavelength, corresponding to a 95% overall increase in average power. Given an almost unchanged measured pulse duration of 260 fs under optimal performance conditions, this related to a signal wavelength peak power output of 18.8 kW, compared with 10 kW using the traditional single-pass geometry. In this study, a total effective peak intensity pump-field of 7.11 GW/cm(2) (corresponding to 3.55 GW/cm(2) from each pump beam) was applied to a 3 mm long periodically poled lithium niobate crystal, which had a damage threshold intensity of 4 GW/cm(2), without impairing crystal integrity. We therefore prove the application of this novel pump geometry provides opportunities for power-scaling of synchronously pumped OPO systems together with enhanced nonlinear conversion efficiency through relaxed damage threshold intensity conditions.
authors.affiliation: Centre for Biophotonics, SIPBS, University of Strathclyde, 27 Taylor Street, Glasgow G4 0NR, UK. greg.norris@strath.ac.uk
authors.forename: G
authors.initials: G
authors.lastname: Norris
authors.forename: G
authors.initials: G
authors.lastname: McConnell
mesh_terms: D004560:Electricity; D017711:Nonlinear Dynamics; D055620:Optical Phenomena; D055095:Optics and Photonics / Q000295:instrumentation*; D009991:Oscillometry / Q000295:instrumentation*