Silicon photonic resonator sensors and devices

Abstract

Silicon photonic resonators, implemented using silicon-on-insulator substrates, are promising for numerous applications. The most commonly studied resonators are ring/racetrack resonators. We have fabricated these and other resonators including disk resonators, waveguide-grating resonators, ring resonator reflectors, contra-directional grating-coupler ring resonators, and racetrack-based multiplexer/demultiplexers. While numerous resonators have been demonstrated for sensing purposes, it remains unclear as to which structures provide the highest sensitivity and best limit of detection; for example, disc resonators and slot-waveguide-based ring resonators have been conjectured to provide an improved limit of detection. Here, we compare various resonators in terms of sensor metrics for label-free bio-sensing in a micro-fluidic environment. We have integrated resonator arrays with PDMS micro-fluidics for real-time detection of biomolecules in experiments such as antigen-antibody binding reaction experiments using Human Factor IX proteins. Numerous resonators are fabricated on the same wafer and experimentally compared. We identify that, while evanescent-field sensors all operate on the principle that the analyte's refractive index shifts the resonant frequency, there are important differences between implementations that lie in the relationship between the optical field overlap with the analyte and the relative contributions of the various loss mechanisms. The chips were fabricated in the context of the CMC-UBC Silicon Nanophotonics Fabrication course and workshop. This yearlong, design-based, graduate training program is offered to students from across Canada and, over the last four years, has attracted participants from nearly every Canadian university involved in photonics research. The course takes students through a full design cycle of a photonic circuit, including theory, modelling, design, and experimentation.

Electrically tunable resonant filters in phase-shifted contra-directional couplers

“…Significant progress has been achieved in this field, including high-speed modulators/switches [1] and on-chip biomedical sensors [2]. To further enhance the tuning/modulation efficiency, it is important to shrink the mode volume in an optical resonator.…”

On-chip sensing with high-Q amorphous silicon microdisk resonators

“…Silicon is a promising platform to fabricate sensors for chemical, medical and biosensing applications, which is mainly due to the ultra-compact size of these resonators, their low limits of detection, the mass fabrication capabilities at low-costs, and the feasibility to fabricate large sensor arrays on a common planar substrate [1][2][3]. Owing to the tight light confinement in high index contrast (HIC) photonic waveguides there is a strong evanescent field at the core cladding interfaces which consequently gives a large response to changes in the surrounding cladding media [4].…”

Label-free photonic biosensors fabricated with low-loss hydrogenated amorphous silicon resonators

“…However, a high Q factor does not necessarily improve the sensitivity, especially for water-based solutions, because water adds substantial propagation loss (≈10 cm −1 at 1550 nm), and a high quality factor often results from a stronger mode confinement in the resonator core and hence less light can effectively interact with the sensing medium. 12,13 Based on these considerations, the homogeneous sensing experiments were carried out with microdisk resonators which exhibit moderate Q-factors of 10 4 although we have already fabricated critically coupled disk resonators with higher intrinsic Q of ≥10 5 for qTE and ≥0.9 × 10 6 for qTM with amorphous silicon.…”