Abstract

Recently, as high efficiency phase-matching method for optical second-harmonic generation (SHG), the quasi-phase-matching method using a periodic structure is attracting a lot of attention. To estimate precisely the SHG efficiency in a periodic structure waveguide, the exact electric-field distribution in a waveguide as a function of a longitudinal coordinate is required. This is true, not only in the case of a corrugated waveguide structure, but also in the case of the periodic domain inversion structure in a LiNbO₃ (LN) waveguide as the domain inversion process also causes a linear refractive-index change. To describe the electric-field distribution, we use an ideal normal-mode expansion, which uses modes for a waveguide of averaged width and refractive index. However, many modes must be considered to estimate the nonlinear polarization exactly and that requires a large amount of calculation.

© 1991 Optical Society of America