Long-wavelength operation of synchronously pumped optical parametric oscillators based on periodically poled LiNbO/sub 3

Summary form only given. The very high parametric gain achievable in periodically poled lithium niobate (PPLN), when pumped by intense short pulses, has allowed synchronously pumped oscillation at wavelengths where very strong idler absorption is present. With appropriate design practical sources operating at idler wavelengths well beyond 6 /spl mu/m are possible. A general design strategy is outlined and results from its implementation are presented. An element in the design strategy includes careful minimisation of signal losses, since these strongly affect performance. For this reason a ring configuration is preferable. The strategy also favours short pulses, and tight focussing at the exit end of the crystal, to maximise signal and pump intensities over the last idler extinction length of the crystal. Despite the strong idler absorption coefficient /spl alpha//sub i/ it is not essential to use a crystal length L which makes /spl alpha//sub i/l, small, and we have operated successfully with /spl alpha//sub i/L /spl sim/ 30.