Lab-on-a-Chip Optical Biosensor Platform: Micro Ring Resonator Integrated with Near-Infrared Fourier Transform Spectrometer

TL;DR

This paper presents a monolithically integrated lab-on-a-chip optical biosensor platform combining a micro-ring resonator and a near-infrared Fourier transform spectrometer on a silicon-on-insulator wafer, enabling compact, sensitive detection without external spectrum analyzers.

Contribution

The work demonstrates the design and experimental validation of an integrated MRR biosensor with an on-chip spectrometer, eliminating the need for external optical spectrum analysis in lab-on-a-chip applications.

Findings

Achieved a spectral resolution of ~3.1 nm with the integrated spectrometer.

Demonstrated a bulk sensitivity of ~73 nm/RIU for the MRR biosensor.

Validated wavelength shift detection through experimental measurements with air and water claddings.

Abstract

A micro-ring-resonator (MRR) optical biosensor based on the evanescent field sensing mechanism has been extensively studied due to its high sensitivity and compact device size. However, a suitable on-chip integrated spectrometer device has to be demonstrated for the lab-on-a-chip applications, which can read the resonance wavelength shift from MRR biosensors based on minuscule changes in refractive index. In this paper, we demonstrated the design and experimental results of the near-infrared lab-on-a-chip optical biosensor platform that monolithically integrates the MRR and the on-chip spectrometer on the silicon-on-insulator (SOI) wafer, which can eliminate the external optical spectrum analyzer for scanning the wavelength spectrum. The symmetric add-drop MRR biosensor is designed to have a free spectral range (FSR) of ~19 nm, and a bulk sensitivity of ~73 nm/RIU; then the drop-port output resonance peaks are reconstructed from the integrated spatial-heterodyne Fourier transform spectrometer (SHFTS) with the spectral resolution of ~3.1 nm and bandwidth of ~50 nm, which results in the limit of detection of 0.042 RIU. The MRR output spectrum with air- and water-claddings are measured and reconstructed from the MRR-SHFTS integrated device experimentally to validate the wavelength shifting measurement.