Limits to the power scalability of high-gain optical parametric oscillators and amplifiers

Recent developments in high-gain optical parametric amplifiers (OPAs) and oscillators (OPOs) have led to interesting picosecond and femtosecond pulse sources with high average power in different wavelength regions. We have investigated this with a combination of analytical and numerical techniques. In this way we have identified a limit on the peak power, and this limit has already been reached in experiments. The limit arises from back conversion, i.e., sum frequency generation from signal and idler. Power limits for various constraints on beam quality (M/sup 2/) and conversional efficiency (/spl eta/) can be seen from the graphs.