Enhanced optical nonlinearities in air-cladding silicon pedestal waveguides

TL;DR

This paper demonstrates enhanced third-order optical nonlinearity in air-cladding silicon pedestal waveguides, showing increased spectral broadening and nonlinear-index coefficient compared to conventional silicon-on-insulator waveguides, due to interaction with confined acoustic phonons.

Contribution

The study introduces an air-cladding silicon pedestal waveguide with higher nonlinearity, supported by experimental measurements and theoretical modeling, advancing nonlinear integrated photonics.

Findings

Nonlinear-index coefficient is about 5% larger in pedestal waveguides.

Enhanced spectral broadening observed from self-phase modulation.

Interaction with confined acoustic phonons increases nonlinearity.

Abstract

The third-order optical nonlinearity in optical waveguides has found applications in optical switching, optical wavelength conversion, optical frequency comb generation, and ultrafast optical signal processing. The development of an integrated waveguide platform with a high nonlinearity is therefore important for nonlinear integrated photonics. Here, we report the observation of an enhancement in the nonlinearity of an air-cladding silicon pedestal waveguide. We observe enhanced nonlinear spectral broadening compared to a conventional silicon-on-insulator waveguide. At the center wavelength of 1555 nm, the nonlinear-index coefficient of air-cladding silicon pedestal waveguide is measured to be about 5% larger than that of a conventional silicon-on-insulator waveguide. We observe enhanced spectral broadening from self-phase modulation of an optical pulse in the pedestal waveguide. The interaction of light with the confined acoustic phonons in the pedestal structure gives rise to a larger nonlinear-index coefficient. The experimental results agree well with the theoretical models.