Biosensing Using Microring Resonator Interferograms

Shih-Hsiang Hsu,Yu-Hou Su,Yung-Chia Yang,Sheng-Min Wang,Ching-Yu Lin,Shih-An Huang

doi:10.3390/s140101184

Abstract

Optical low-coherence interferometry (OLCI) takes advantage of the variation in refractive index in silicon-wire microring resonator (MRR) effective lengths to perform glucose biosensing using MRR interferograms. The MRR quality factor (Q), proportional to the effective length, could be improved using the silicon-wire propagation loss and coupling ratio from the MRR coupler. Our study showed that multimode interference (MMI) performed well in broad band response, but the splitting ratio drifted to 75/25 due to the stress issue. The glucose sensing sensitivity demonstrated 0.00279 meter per refractive-index-unit (RIU) with a Q factor of ∼30,000 under transverse electric polarization. The 1,310 nm DFB laser was built in the OLCI system as the optical ruler achieving 655 nm characterization accuracy. The lowest sensing limitation was therefore 2 × 10−4 RIU. Moreover, the MRR effective length from the glucose sensitivity could be utilized to experimentally demonstrate the silicon wire effective refractive index with a width of 0.45 μm and height of 0.26 μm.

Highlights

Optical waveguide sensors have attracted considerable attention due to their immunity to electromagnetic interference, good compactness and robustness and high compatibility with fiber networks, while exhibiting shorter response times and higher sensitivities [1]
Most microring resonator (MRR) use the resonating wavelength shift induced by the cladding layer refractive index change in biosensing applications
If polarization is applied to the MRR for different glucose sensing levels, the silicon wire effective index of refraction and birefringence can be derived from MRR

Summary

Introduction

Optical waveguide sensors have attracted considerable attention due to their immunity to electromagnetic interference, good compactness and robustness and high compatibility with fiber networks, while exhibiting shorter response times and higher sensitivities [1]. Most MRRs use the resonating wavelength shift induced by the cladding layer refractive index change in biosensing applications. MZ interferometer and a continuous-wave broad-band source used to characterize the high Q MRR on one MZ arm using the optical ruler for resolution enhancement. Since the optical paths between the optical ruler and DUT are different, a high coherent short wavelength with free space light tracking could be applied to the optical ruler for higher sensitivity. Refractive index sensors usually use the optical power or wavelength related for sensing. The former sensitivity is affected by the light power fluctuation and the sensitivity of the latter is limited by the availability of a costly high resolution optical spectrum analyzer (OSA). Different glucose concentrations could be derived using silicon-wire waveguide birefringence from relative interferogram movement distances

Design and Theory

Experiments and Discussions

Findings

Conclusions