UBC Theses and Dissertations
Improving the performance of silicon photonic optical resonator-based sensors for biomedical applications Luan, Enxiao
Silicon photonic biosensors show great potential for applications in medical diagnostics and healthcare services. Near-infrared transparency and high refractive index of silicon allow us to build compact and efficient circuits leveraging CMOS foundries, which provide low-cost mass production and enable the integration of the optoelectronic components on the same chip. Although silicon photonic biosensors have proven performances close to today's gold standard diagnostics, many applications still require higher multiplexing, as well as more sensitive, reliable and quantitative measurements. This dissertation is based on theoretical and experimental studies of silicon photonic sensing architectures in terms of sensor performance improvement and unit-cost reduction. Specifically, two novel sub-wavelength grating-based (SWG) waveguide configurations are presented to improve the sensitivity. Leveraging the advantage of SWG metamaterials, the substrate-overetch (SOE) and multi-box SWG devices present a largely extended modal size and surface contact area, which gives 10-time enhanced sensitivity compared to the conventional devices. In addition, by employing the Bragg grating as the sensing architecture, the multi-box SWG-based grating configuration achieves a lower detection limit compared to the microring resonator (MRR) counterpart and demonstrates the capability for monitoring small molecule interactions. Replacing the laser with a broadband source can provide a lower-cost solution for the optical system. Therefore, two cost-effective broadband light source-based sensing implementations are proposed and demonstrated with acceptable sensitivities. The first implementation uses cascaded MRRs for index monitoring, where the analyte variation is converted to the photocurrent change as the readout. The second implementation uses a phase-shifted Bragg grating-based symmetrical Mach-Zehnder interferometer, where the analyte variation maps the intensity change at the resonant wavelength. Furthermore, a system-level integration of active silicon photonic sensors using Fan-Out Wafer-Level-Packaging (FOWLP) is proposed in the dissertation, which can reduce the die size down to 1 mm² while simplifying the microfluidic and optical integration. Leveraging the CMOS foundries and the proposed FOWLP technique, the unit cost of each packaged sensing die can be reduced to several dollars.
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Attribution-NonCommercial-NoDerivatives 4.0 International