Simultaneous second-harmonic generation with two orthogonal polarization states in periodically poled KTP

Simultaneous generation of second-harmonic light with orthogonal polarizations in the blue spectral region is demonstrated by use of type II and type I quasi-phase matching for the nonlinear coefficients d(33), d(24), and d(32) in periodically poled KTP. The second-harmonic power ratio in both polarization states can be tuned by the fundamental polarization and (or) the periodically poled KTP temperature. Femtosecond pulse frequency-doubling efficiencies of as much as 39.5% W-1 and 8.1% W-1 are demonstrated in 7-mm periodically poled KTP for type I and type Il processes, respectively. The efficiency limitations caused by various effects of the group-velocity mismatch are discussed. (C) 2002 Optical Society of America.