Force-induced optical nonlinearity and Kerr-like coefficient in opto-mechanical ring resonators

Y F Yu,C S Tan,T Bourouina,J M Tsai,M Ren,A Q Liu,J B Zhang

doi:10.1364/oe.20.018005

Abstract

This paper demonstrates the optical nonlinearity in opto-mechanical ring resonators that consist of a bus waveguide and two ring resonators, which is induced by the optical gradient force and characterized by the Kerr-like coefficient. Each ring resonator has a free-hanging arc that is perpendicularly deformable by an optical gradient force and subsequently this deformation changes the effective refractive index (ERI) of the ring resonator. The change of the ERI induces optical nonlinearity into the system, which is described by an equivalent Kerr coefficient (Kerr-like coefficient). Based on the experimental results, the Kerr-like coefficient of the ring resonator system falls in the range from 7.64 × 10(-12) to 2.01 × 10(-10) m(2)W(-1), which is at least 6-order higher than the silicon's Kerr coefficient. The dramatically improved optical nonlinearity in the opto-mechanical ring resonators promises potential applications in low power optical signal processing, modulation and bio-sensing.

Highlights

Optical nonlinearity is a material property, which is defined as the nonlinear response of the polarization P to the electric field E of light when light is propagating in the material
Ion doping is used to change the optical nonlinearity of the silicon [7], but it induces a large free-carrier absorption, which decreases the capability of light intensity enhancement in the silicon–based devices
The optical ring resonator enlarges the opto-mechanical effect via the increase in light intensity, which is widely applied in mesoscale back action [13], sideband cooling [14], thermal nonlinearity [15,16,17] and photonic structure controlling [18]

Summary

Introduction

Optical nonlinearity is a material property, which is defined as the nonlinear response of the polarization P to the electric field E of light when light is propagating in the material. Due to the optical nonlinearity of materials, a variation of the refractive index is induced, which is proportional to the local intensity of light and can be expressed as n = n0 + n2I , where n0 is the refractive index, and n2 is a constant. This phenomenon is well known as the optical Kerr effect and n2 is defined as the Kerr coefficient. The theoretical analysis, the numerical simulations and the experimental results are presented and discussed

Theoretical analysis

Experimental results and discussions

Conclusions