Abstract

Second-harmonic generation using waveguides is attractive because the tight spatial confinement results in high conversion efficiencies at relatively low power levels. Because of the small refractive-index differences produced by waveguide-fabrication techniques in inorganic materials such as LiNbO₃, the guided modes can be very closely spaced. Furthermore, a single-mode waveguide at the fundamental wavelength is typically multimode for the second harmonic. Power exchange between one of these SH modes and the fundamental can lead to a nonlinear phase shift for the other SH modes. For large conversion efficiencies and closely spaced modes we found that the second-harmonic- generation process can be severely distorted by this nonlinear phase change.

© 1995 Optical Society of America