Second-harmonic generation in periodically poled lithium niobate waveguides fabricated by femtosecond laser pulses

The authors have demonstrated the second-harmonic generation (SHG) in optical channel waveguides which were fabricated in periodically poled lithium niobate (PPLN) by tightly focused femtosecond laser (781nm) pulses. The measured quasi-phase-matched wavelength and 3dB bandwidth for SHG in a 44.8-mm-long PPLN waveguide which has a domain period of 16.6μm were about 1563 and 0.25nm, respectively. The value of the index difference between the fundamental and harmonic wavelengths in laser written waveguide was inferred to be 0.047.