Second harmonic generation of femtosecond laser written depressed cladding waveguides in periodically poled MgO:LiTaO crystal.

We report on the fabrication of depressed cladding waveguides in periodically poled MgO doped LiTaO by using low-repetition-rate femtosecond laser writing, and their use for guided-wave second harmonic generation (SHG). The cladding waveguides exhibit different guiding performance along the extraordinary and ordinary polarizations. The temperature-dependent quasi-phase-matching (QPM) is realized to obtain SHG in the depressed cladding waveguides. The results show that the QPM temperature was dependent on the poling period and on the features of the cladding waveguides. The highest nonlinear conversion efficiency (0.74%Wcm) was found in the waveguide fabricated with large scanning velocity (0.75 mm/s) and small radius (15 μm).