High average power frequency doubling

High average power second harmonic generation in crystals with finite absorption at the fundamental or harmonic wavelength creates unique problems. In addition to generating significant OPD which degrades the beam quality, heating of the crystal creates conditions which can be inherently temporally unstable. As the crystal is tuned towards phase matching, rapid changes in temperature cause the crystal to drift away from phase matching conditions which is followed by reduced frequency conversion. Experiments are in progress with three crystals, KTP, KD*P and KNbO₃, which have vastly different characteristics, to assess their potential for high average power doubling