Nonlinear optics in wavelength-size waveguides: how far can the conversion efficiency be pushed?

Abstract

When their size approach the wavelength of light propagating in them, waveguides exhibit favorable properties such as high nonlinearity and strong confinement. These properties have been used for a variety of nonlinear effects, including supercontinuum generation, second-, third- and one-third- harmonic generation, pulse shaping and nonlinear switching.Although simulations predicted conversion efficiencies well in excess of 30% for most of harmonic generation, experiments showed conversions of a fraction of a percent, at best.This talk will discuss harmonic generation in wavelength-size waveguides and limitations to the practical achievement of theoretical efficiency. In particular, intrinsic surface roughness due to thermal surface waves frozen during fabrication provide a constantly changing detuning from the ideal phase matching conditions, considerably reducing the overall efficiency for waveguides longer than 1mm