Bandwidth characteristics of a pulsed optical parametric oscillator: application to degenerate four-wave mixing spectroscopy.

Factors influencing the optical bandwidth of a free-running pulsed beta-barium borate optical parametric oscillator are examined and incorporated in a simple fitting procedure. Spatiospectral phenomena in the optical parametric oscillator output beam are thereby identified; these suggest a novel way to reduce the effective optical bandwidth for spectroscopic purposes. This technique is demonstrated by recording a degenerate fourwave mixing spectrum of sodium atoms in an air-acetylene flame.