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 , , and 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 and are demonstrated in 7-mm periodically poled KTP for type I and type II processes, respectively. The efficiency limitations caused by various effects of the group-velocity mismatch are discussed.
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