An injection seeded narrow bandwidth pulsed optical parametric oscillator and its application to the investigation of hyperfine structure in the PF radical

We describe the construction of an all solid-state, narrow bandwidth, pulsed optical parametric oscillator (OPO) based on beta -barium borate nonlinear crystals. The OPO was injection seeded by an external cavity diode laser in the range 755-855 nm to generate high power narrow bandwidth tunable light in this range and simultaneously at 606-669 nm. The bandwidth of the visible light was similar to 130 MHz, and after frequency doubling or sum frequency mixing with the second harmonic of the pump Nd:YAG laser, sub-Doppler spectra with an overall resolution of 450 MHz were taken in the UV. The system is demonstrated by taking high-resolution spectra of the v(')=2-3 and 5-7 bands of the A (3)Pi -X (3)Sigma (-)(v('),0) progression and the v(')=4-v(')=0 band of the d (1)Pi -a (1)Delta transition in PF. These spectra show clear hyperfine structure, and an analysis of this structure is presented and interpreted in terms of the electronic structure of the molecule. As a prelude to this high-resolution study, the first ten members of the A-X band system and the first five members of the d-a band system were recorded at the moderate resolution provided by a pulsed dye laser. (C) 2001 American Institute of Physics.