Abstract
Broadband intracavity-absorption spectroscopy is demonstrated in a singly idler-resonant optical parametric oscillator made of β-barium borate, pumped by the third harmonic of an injection-seeded Q-switched Nd:YAG laser. IR 1.53-μm absorption of idler radiation by transitions of acetylene is detected with enhanced sensitivity in the upconverted spectrum of the signal radiation at 461 nm. Quantitative comparison of computer-simulated pulse-energy spectra with experimental absorption spectra indicates that the experimental detection sensitivity is close to the theoretical limit.