Phase-matching properties of PPKTP, MgO:PPSLT and MgO:PPcLN for ultrafast optical parametric oscillation in the visible and near-infrared ranges with green pump

Ultrashort pulses with wavelength tuning in the visible and near-infrared (VNIR) ranges (here approximately 680 to 2000 nm) have wide application in many biomedical devices especially in imaging and spectroscopy. The theoretical studies here consider the phase-matching conditions of three periodically poled crystals (PPKTP, MgO:PPcLN and MgO:PPSLT) to use for femtosecond optical parametric oscillators (OPO) to generate wavelength tunability in this range. The basic optical properties and the wavelength tuning ranges are calculated with respect to different grating periods and temperature variation. Dispersive properties of crystals relevant to the ultrafast operation regime are also discussed. The excitation wavelength used here for the analysis is 520 nm which is the second harmonic wavelength of Yb-doped ultrashort pulse solid state lasers. The concept of the tunable femtosecond OPOs with green excitation presented here can be a better alternative to the widely used expensive Ti:Sapphire lasers.