Lateral lattice shift engineered slow light in elliptical photonics crystal waveguides

Bo Li,Chengkuo Lee,Fu-Li Hsiao,Chong Pei Ho

doi:10.1117/1.jnp.8.084090

Bo Li, Chengkuo Lee + Show 2 more

Open Access

https://doi.org/10.1117/1.jnp.8.084090

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Abstract

A photonics crystal (PhC) waveguide that operates in the slow-light regime is reported in this paper. A second line of circular air holes from the PhC waveguide in a triangular lattice is replaced by a line of elliptical air holes. Based on a three-dimensional plane wave expansion, the lateral shift of elliptical air holes is conducted to enhance the slow-light characteristics. A group index of 166 and a delay-bandwidth product of 0.1812 are derived from an optimized PhC using elliptical air holes with a lateral shift of 160 nm according to the simulation results. A Mach–Zehnder interferometer (MZI) is integrated with the above-mentioned PhC waveguide with a 17 μm length in one of its arms. The measured transmission spectrum of the fabricated MZI embedded with a PhC waveguide shows slow-light interference patterns.

Highlights

In recent decades, photonics crystal (PhC), because of its fundamental significance and promising optical performance, has attracted more and more research effort around the world
The bandwidth of the PhC waveguide expands to its maximum value at ΔL 1⁄4 160 nm and it narrows down as the ellipse lattice further shifts, while the group index peak is observed in the plot
The group index and the bandwidth are 166 and 1.69 nm at the shift distance of 160 nm, where a maximum delay-bandwidth product (DBP) is derived as 0.1812. By considering both data of the group index and the dispersion, we fabricated and tested the designed PhC waveguide with the elliptical air holes with a lateral shift of 160 nm

Summary

Introduction

Photonics crystal (PhC), because of its fundamental significance and promising optical performance, has attracted more and more research effort around the world. Slow light enhances the nonlinear optical effect in the PhC waveguide, as the intensity scales with the slowdown factor.[15,16] The strong localized electric field of the slowlight region enables and enhances liquid and gas sensing.[17,18] High-order dispersion usually occurs and distorts the optical signals in the case of devices having a long optical path. To eliminate such distortion, several zero-dispersion devices were developed.[19,20,21,22,23] a coupledresonator optical waveguide based on PhC cavities or microrings can help in compensation of the slow-light device distortions.[24,25]. To demonstrate the slow-light effect, we fabricate slow-light devices comprising a Mach–Zehnder interferometer (MZI) embedded with the PhC waveguides based on the optimized lattice shift results

Design and Modeling

Design Ellipse without shift

Device Fabrication and Characterization

Findings

Conclusion