Silicon Photonics Mach-Zehnder Biosensor with Coherent Detection for Point-of-Care Devices

Abstract

Integrated photonic biosensors are a highly promising technology platform for biochemical diagnostics. In general, they have demonstrated impressively low detection limits and can offer highly multiplexed operations in real time. Ring-resonator-based photonic biosensors have been shown to be a practical solution for lab-on-chip solutions and first commercial products are already available. However, they mostly require an expensive high-quality laser for accurate operation. In recent years, interferometer-based photonic sensors have demonstrated even lower detection limits as well as multiplexation capabilities and are candidates for future point-of-care devices for primary care, directly at the patient site. Point-of-care solutions require a portable and inexpensive device. The read-out, i.e. optical source, detection scheme, and signal processing, typically make up a significant part of an integrated photonic biosensor system’s price. Ring-resonator-based systems often need a tunable narrow-linewidth laser as optical source to extract the resonance wavelength, whereas interferometers just need a fixed wavelength source to accurately extract the phase shift, but can suffer from sensitivity fading and ambiguity. In this thesis we investigate a coherently read symmetric Mach-Zehnder interferometer that overcomes these drawbacks and show that it is an attractive solution for point-of-care devices for several reasons.