Multi-slot photonic crystal cavities for high-sensitivity refractive index sensing.

Peipeng Xu,Jun Zhou,Arka Majumdar,Jiajiu Zheng,Yueyang Chen,Chen Zou

doi:10.1364/oe.27.003609

Abstract

We present the design, fabrication, and characterization of a multi-slot photonic crystal (PhC) cavity sensor on the silicon-on-insulator platform. By optimizing the structure of the PhC cavity, most of the light can be distributed in the lower index region; thus, the sensitivity can be dramatically improved. By exposing the cavities to different mass concentrations of NaCl solutions, we obtained that the wavelength shift per refractive index unit (RIU) for the sensor is 586 nm/RIU, which is one of the highest sensitivities achieved in a non-suspended cavity. Furthermore, the size of the sensing region of the reported sensor is only 22.8 μm × 1.5 μm, making the high-sensitivity PhC cavity sensor attractive for the realization of on-chip sensor arrays.

Highlights

Lab-on-a-chip (LOC), which integrates many of the analytical capabilities of a biomedical research lab into a small disposable chip, can provide instant, multiplexed, and cost-effective measurements at the point of need compared with a centralized laboratory [1,2]
1D Photonic crystal (PhC) cavities are intriguing in sensing community owing to their compact size and enhanced light-matter interaction due to ultra-high Q-factor and low mode volumes ~(λ/n
The total amount of analytes required to produce a measurable change in the refractive index can be extremely tiny resulting in a very high sensitivity

Summary

Introduction

Lab-on-a-chip (LOC), which integrates many of the analytical capabilities of a biomedical research lab into a small disposable chip, can provide instant, multiplexed, and cost-effective measurements at the point of need compared with a centralized laboratory [1,2]. In resonator-based architectures, a tiny change in the external refractive index can make a noticeable shift of the resonance frequencies and, provide a measurable response. Among these different structures, 1D Photonic crystal (PhC) cavities are intriguing in sensing community owing to their compact size and enhanced light-matter interaction due to ultra-high Q-factor and low mode volumes ~(λ/n). We demonstrate a multi-slot PhC cavity (MSPhC) in silicon, which consists of four nanogaps with a width of 70 nm Benefiting from this design, the sensitivity of the PhC sensors is highly improved. The device can be employed to detect proteins in ultra-low concentration with the appropriate choice of antibody

Design and analysis

Findings

Summary