Optical parametric oscillation out to 6.3µm in periodically poled lithium niobate under strong idler absorption

The very high gains, achieved when using mode-locked pulses to synchronously pump an optical parametric oscillator based on periodically poled lithium niobate, permit oscillation even with strong idler absorption. Oscillation has been achieved at idler wavelengths out to 6.3 µm. Idler power was directly measured out to 5.41µm. Beyond this, idler generation was inferred from the observed signal. We present an analysis of operation in the presence of strong idler absorption