Pulsed OPO brightness improvement by means of intracavity spatial filtering

The design and operation of a pulsed optical parametric oscillator (OPO) wi th an intracavity spatial filter is described. This filter, designed to sel ect a single high-order transverse mode, improves the brightness of the gen erated parametric waves by decreasing their divergence. This process is con firmed by experiments carried out on a KTP OPO pumped at 532 nm, operating close to degeneracy in a singly resonant regime. Comparison of the output e nergy and beam quality for the OPO with and without intracavity filtering d emonstrated a five-fold increase in brightness. (C) 1999 Elsevier Science B .V. All rights reserved.