Silicon-Nitride-Based Integrated Optofluidic Biochemical Sensors Using a Coupled-Resonator Optical Waveguide

Abstract

Citation:Wang J, Yao Z and Poon AW (2015) Silicon-nitride-based integrated optofluidic biochemical sensors using a coupled-resonator optical waveguide. Front. Mater. 2:34. doi: 10.3389/fmats.2015.00034 Silicon-nitride-based integrated optofluidic biochemical sensors using a coupled-resonator optical waveguide Silicon nitride (SiN) is a promising material platform for integrating photonic components and microfluidic channels on a chip for label-free, optical biochemical sensing applications in the visible to near-infrared wavelengths. The chip-scale SiN-based optofluidic sensors can be compact due to a relatively high refractive index contrast between SiN and the fluidic medium, and low-cost due to the complementary metal-oxide-semiconductor (CMOS)-compatible fabrication process. Here, we demonstrate SiN-based integrated optofluidic biochemical sensors using a coupled-resonator optical waveguide (CROW) in the visible wavelengths. The working principle is based on imaging in the far field the outof-plane elastic-light-scattering patterns of the CROW sensor at a fixed probe wavelength. We correlate the imaged pattern with reference patterns at the CROW eigenstates. Our sensing algorithm maps the correlation coefficients of the imaged pattern with a library of calibrated correlation coefficients to extract a minute change in the cladding refractive index. Given a calibrated CROW, our sensing mechanism in the spatial domain only requires a fixed-wavelength laser in the visible wavelengths as a light source, with the probe wavelength located within the CROW transmission band, and a silicon digital charge-coupled device/CMOS camera for recording the light scattering patterns. This is in sharp contrast with the conventional optical microcavity-based sensing methods that impose a strict requirement of spectral alignment with a high-quality cavity resonance using a wavelength-tunable laser. Our experimental results using a SiN CROW sensor with eight coupled microrings in the 680 nm wavelength reveal a cladding refractive index change of~1.3 × 10 −4 refractive index unit (RIU), with an average sensitivity of 281 ± 271 RIU −1 and a noise-equivalent detection limit of 1.8 × 10 −8~1 .0 × 10 −4 RIU across the CROW bandwidth of~1 nm.

Silicon‐Based Integrated Label‐Free Optofluidic Biosensors: Latest Advances and Roadmap

“…[ 185 ] The calibrated sensing system only requires a fixed‐wavelength laser diode and a CMOS camera. [ 186 ] In the latest demonstrations of streptavidin detection using surface‐functionalized CROWs, the varying light scattering patterns are recorded and analyzed through a correlation algorithm so that the relative spectral shift can be readily extracted. [ 85,187 ] In this scheme, an on‐chip spectrometer such as an AWG is circumvented, which largely minimizes the sensor footprint and facilitates multiplexed detection on a single chip.…”

Whispering Gallery Mode Optical Microresonators: Structures and Sensing Applications

“…Utilizing the split of eigenstates and direct imaging of elastic scattering patterns of multiple eigenstates in a CROW system, researchers have elegantly demonstrated a simple and straightforward scheme for RI sensing and protein detection without wavelength‐scanning step. This concept has provided a new idea for the research of integrated optical biochemical sensors with high performance, reliability and compactness, and laid a foundation for the follow‐up research …”

CMOS Nanophotonic Sensor With Integrated Readout System

“…Over the last decade nanophotonic sensors have improved tremendously in terms of sensitivity and detection limit by using different sensor designs made of different materials [4]- [9]. Furthermore, the size of the nanophotonic sensor chips has reduced by exploiting different physical phenomena via various design configurations and compact integration of nanophotonic structures on the sensor chip [10]- [15]. However, while the nanophotonic sensor chips are small, their readout requires large and expensive laboratory-based equipment such as laser, spectrometer, optical spectrum analyzer (OSA) or detector.…”