Silicon Photonics Suspended Ring Resonator Biosensor with Integrated On-Chip Optical Readout

  • Soha E. Yousuf

Student thesis: Doctoral Thesis


Sensor applications as real-time, label-free 'lab-on-a-chip' have posed an urgent need at significantly higher sensitivities than current state-of-the art technology. Despite this, highly sensitive and accurate sensors have been challenging to realize due to compromises such as cost, sensitivity, selectivity, footprint, and temperature stability. To this end, significant interest has escalated in the development and research of optical sensors that are regarded as valuable due to their small footprint, large sensitivity, wide dynamic range and multiplexing capabilities. The presented work is a theoretical and experimental study of optical sensing devices based on micro-ring resonators, as well as an efficient sensor system created using these proposed devices on a potentially scalable low-cost silicon-on-insulator (SOI) platform with a proven two-fold increase in sensitivity performance. The sensors and corresponding optical readout system have been developed for silicon photonics platform with the prospect of locally removing the buried oxide to generate suspended silicon structures. A novel suspended microring resonator sensor using internal sub-wavelength gratings was presented and demonstrated, with achieved Q factors above 100k, an intrinsic limit of detection on the order of 10-5 RIU, and very high predicted sensitivities of 500-800 nm/RIU, that ranges well in comparison to values in literature. Sensing experiments with the sensor device were conducted with gas mixtures (achieving an intrinsic limit of detection of 60 ppm). A 90 nm slab micro-ring resonator structure was also presented in a bio-sensing demonstration with 25 base-pairs ssDNA/morpholino hybridization using a covalently functionalized surface (250 Pico molar detection, limited by available test samples). Finally, a novel sensor system with integrated optical readout that is capable of working with low-cost, fixed-wavelength continuous wave lasers and low-cost broadband light sources to monitor resonant wavelength shifts has been proposed and presented, as an alternative to using expensive tunable lasers.
Date of AwardMay 2020
Original languageAmerican English


  • Silicon Photonics; Optical Sensor; Sub-wavelength grating; DNA Hybridization; Sensor System.

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