Practical mid-infrared picosecond optical parametric oscillator for the 4-6 μm spectral range

Tunable picosecond pulses in the mid-infrared (mid-IR) are of interest for time-resolved spectroscopy of narrow-bandgap semiconductors and the optical parametric oscillator (OPO) is an attractive source for the generation of such pulses. In the domain of commonly available, low to moderate power laser sources, the most viable material candidates for mid-IR pulse generation at present are periodically-poled LiNbO3 (PPLN), and the arsenate isomorphs of KTP such as PPRTA and PPKTA. The large nonlinearity of these materials combined with noncritical phase-matching and a transparency range extending beyond 5 μm allows the development of practical picosecond OPOs using widely available mode-locked Ti:Sapphire (Ti:S) and Nd-based laser.