Structural tuning of guiding modes of line-defect waveguides of silicon-on-insulator photonic crystal slabs

We experimentally demonstrate the structural tuning of the waveguiding modes of line defects in photonic crystal (PC) slabs. By tuning the defect widths, we realized efficient single-mode waveguides that operate within photonic band gap frequencies in silicon-on-insulator PC slabs. The observed waveguiding characteristics agree very well with three-dimensional finite difference time-domain calculations. We also directly measured the propagation loss of the line defect waveguides and obtained a value of 6 dB/mm.

I. Introduction

Certain types of photonic crystals (PCs) can possess a photonic bandgap (PBG) and thus become equivalent to a photonic insulator [1], [2]. Such photonic insulators are expected to serve as a basic platform for photonic integrated circuits (PICs) because we can utilize the strong two-dimensional (2-D) or three-dimensional (3-D) confinement that results from the existence of the PBGs. By incorporating structural defects into PCs with PBGs, various functional components can be implemented, which is analogous with doping into insulators in electronic crystals [3]. Line defects can work as strongly confined waveguides and point defects work as ultrasmall high-Q resonators. These functional defects will be key components of PC-based integrated circuits.