Synchronously pumped optical parametric oscillator with diffraction-grating tuning

The operating characteristics of a synchronously pumped optical parametric oscillator, based on periodically poled lithium niobate (PPLN), with a diff raction grating as the tuning element, are described and compared with desi gn expectations. Operation at average signal output power levels of up to 2 .0 W has been achieved and signal/idler tuning in the range 1.466-3.663 mum has been investigated using the tilt of the diffraction grating, while kee ping the temperature of the PPLN fixed. A detailed investigation has been m ade of the operating characteristics that might be influenced by the presen ce of pulse tilt caused by the grating. It is shown that any adverse effect s of tilt on beam quality can be small, with the main observed effect being an excess loss. An observed tendency to oscillate in higher-order transver se modes on the long-wavelength side of the tuning range is ascribed to non -collinear phase-matching. This higher-order-mode oscillation is easily pre vented by the insertion of an aperture. The analysis presented here include s a grating loss calculation and the calculation of the tuning range achiev able with a diffraction grating. The effects of cavity-length change on osc illator performance are also examined and it is found that the grating can give a valuable stabilizing influence by suppressing cavity-length-induced frequency-puffing effects. Extension of the use of gratings from the picose cond to the femtosecond regime is also considered.