Second harmonic generation in a domain-inverted MgO-doped LiNbO3 waveguide by using a polarization axis inclined substrate

We demonstrate quasiphase matched second harmonic generation by use of annealed proton-exchanged 87 degrees Z-cut MgO 5 mol% doped LiNbO3 (MgO:LN) waveguides supporting a TE-mode guided wave. Formation of a domain inversion was achieved by applying electric fields in 3 degrees Y-cut and 87 degrees Z-cut MgO:LN. In 3 degrees Y-cut and 87 degrees Z-cut MgO:LN substrates, a polarization axis inclines at an angle theta equal to 3 degrees to the surface. The domain inversion was formed in a direction parallel to the polarization axis like needles stuck into the substrate. The depth of the domain inversion was 2.5 mu m with a period of 4.75 mu m. The depth was about 2.5 times deeper than that in X-and Y-cut substrate at an angle theta equal to 0 degrees. By forming a waveguide on the domain-inverted substrate, a blue light of wavelength 475 nm, and a power of 37 mW has been obtained and a normalized second harmonic conversion efficiency was 300%/W cm(2) with interaction length of 10 mm, using a tunable external cavity laser diode as a fundamental wave source. (C) 1997 American Institute of Physics.