Wide-band slow light in compact photonic crystal coupled-cavity waveguides

Momchil Minkov,Vincenzo Savona

doi:10.1364/optica.2.000631

Abstract

Slow light has a variety of applications, in particular for enhanced nonlinear effects like four-wave mixing and high-harmonic generation. Here, we propose a photonic crystal coupled-cavity waveguide with an ultracompact arrangement of the constituent cavities in the propagation direction, and use an optimization algorithm to tune several structural parameters to engineer slow light with a constant group index ng over a wide bandwidth. We propose several specific silicon designs, including one with ng≈37 over a 20 nm wavelength range and another one with ng≈116 over an 8.8 nm band, which yields a group index–bandwidth product of 0.66—a record value among all slow-light devices. The design is experimentally beneficial because of its small footprint and straightforward fabrication and could find applications in optical storage or switching, and in generating quantum states of light.

Highlights

One of the major research goals in the field of photonics is enhancing light–matter interactions and the resulting optical nonlinearities
A different approach—better suited for some applications [5]—involves slowing down the light propagation in a one-dimensional structure engineered for a low group velocity where, again, silicon photonic crystal (PhC) have led to impressive results [6], in line-defect waveguide systems [7,8,9,10] and in coupled-cavity waveguides (CCWs, called coupled-resonator optical waveguides) [11,12,13,14,15,16,17]
The group index ng c∕vg, with vg being the group velocity, is the slow-down factor as compared to the light propagation in vacuum, and nonlinear effects typically scale with this quantity

Summary

Introduction

One of the major research goals in the field of photonics is enhancing light–matter interactions and the resulting optical nonlinearities. A different approach—better suited for some applications [5]—involves slowing down the light propagation in a one-dimensional structure engineered for a low group velocity where, again, silicon PhCs have led to impressive results [6], in line-defect waveguide systems [7,8,9,10] and in coupled-cavity waveguides (CCWs, called coupled-resonator optical waveguides) [11,12,13,14,15,16,17].

Results

Conclusion