Second Harmonic Generation in Deeply Sub-Wavelength Waveguides

TL;DR

This paper theoretically explores second harmonic generation in ultra-narrow waveguides, revealing a new guiding mechanism that enables efficient frequency doubling despite phase mismatch and diffraction limitations.

Contribution

It introduces a novel guiding mechanism in sub-wavelength waveguides that facilitates second harmonic generation under conditions typically unfavorable for nonlinear interactions.

Findings

Identification of a light trapping phenomenon in sub-wavelength waveguides.

Demonstration of second harmonic generation despite phase mismatch.

Suppression of diffraction and cut-off effects in ultra-narrow waveguides.

Abstract

We theoretically investigate second harmonic generation in extremely narrow, sub-wavelength semiconductor and dielectric waveguides. We discuss a novel guiding mechanism characterized by the inhibition of diffraction and the suppression of cut-off limits in the context of a light trapping phenomenon that sets in under conditions of general phase and group velocity mismatch between the fundamental and the generated harmonic.