Three Photon Absorption in Optical Parametric Oscillators Based on   OP-GaAs
  We report on the first singly-resonant (SR), synchronously pumped optical parametric oscillator (OPO) based on orientation-patterned gallium arsenide (OP-GaAs). Together with a doubly resonant (DR) degenerate OPO based on the same OP-GaAs material, the output spectra cover 3 to 6 ${\mu}$m within ~3 dB of relative power. The DR-OPO has the highest output power reported to date from a femtosecond, synchronously pumped OPO based on OP-GaAs. We discovered strong three photon absorption with a coefficient of 0.35 ${\pm}$ 0.06 cm${^3}$/GW${^2}$ for our OP-GaAs sample, which limits the output power of these OPOs as mid-IR light sources. We present a detailed study of the three photon loss on the performance of both the SR and DR-OPOs, and compare them to those without this loss mechanism. 
Oliver H. Heckl, Bryce J. Bjork, Georg Winkler, P. Bryan Changala, Ben   Spaun,1 Gil Porat, Thinh Q. Bui, Kevin F. Lee, Jie ...
physics.optics physics.chem-ph