SLM operation of a high repetition rate BBO Optical Parametric Oscillator pumped by DPSSL at 355 nm

Single longitudinal mode (SLM) operation of a high repetition rate (1 kHz) nanosecond Type-II BBO optical parametric oscillator (OPO), pumped by the third harmonic (355 nm) of a Diode Pumped Solid State Laser (DPSSL), is demonstrated using a single intra-cavity etalon. Implementation of the cylindrical focusing configuration of the pump beam along with its double passing geometry through the nonlinear OPO crystal has facilitated a low threshold (similar to 0.7 mJ/pulse @355 nm) operation with narrow spectral linewidth (similar to 150 GHz) output. Operations of the OPO at such a low threshold has enabled to maneuver insertion of an intra-cavity etalon for further reducing the spectral linewidth, which allows the OPO to provide SLM lasing output over the spectral range 500-600 nm. The spectral characteristics of the SLM OPO are studied in detail. The time-averaged spectral linewidth of the SLM OPO is measured to be less than 250 MHz.