Abstract

High repetition rate, synchronously pumped optical parametric oscillators (OPOs) have been widely used to extend the tuning wavelength range that can be accessed by conventional femtosecond and picosecond lasers.¹ The oscillation frequency of an OPO can be controlled in several different ways. One technique involves tuning the pump wavelength, while another involves changing the crystal parameters such as the temperature and angle (birefringent phase-matching) or the grating period (quasi-phase matching). In a third method, perhaps the simplest of all, tuning is effected by adjusting the OPO cavity length. In general, this is possible due to the fact that OPO oscillation is achieved under synchronous pump conditions, so that shorter (longer) signal wavelengths will oscillate for shorter (longer) OPO cavities in view of the inherent normal dispersion of the nonlinear crystal. In this paper, we report the characterisation of an OPO that exhibits a distinctive (and anomalous) tuning behaviour when the cavity length tuning procedure is applied.

© 2002 Optical Society of America