Femtosecond laser writing of waveguides in periodically poled lithium niobate preserving the nonlinear coefficient

Optical waveguides have been inscribed in periodically poled lithium niobate by femtosecond laser pulses with the multiscan technique. Second harmonic generation experiments from a fundamental wavelength of 1567 nm demonstrate that the nonlinear optical coefficient in the waveguides is preserved, yielding a conversion efficiency of 18% W-1.