Vernier-cascade silicon photonic label-free biosensor with very large sensitivity and low-cost interrogation

Abstract

Recently, cheap silicon-on-insulator label-free ring resonator biosensors have been demonstrated that allow fast and accurate quantitative detection of biologically relevant molecules for applications in medical diagnostics and drug development. However, a further improvement of their detection limit is limited by their small sensitivity and an expensive tunable laser is typically required to resolve the sharp resonances for wavelength interrogation. Therefore, we experimentally investigated the use of a Vernier-cascade sensor that achieves a sensitivity (thousands of nm/RIU) that is an order of magnitude larger than that of a ring resonator sensor (approx. 100 nm/RIU), while still maintaining sharp spectral features that allow precise monitoring of spectral shifts with data-fitting. Moreover we prove that it's also possible to accurately interrogate the sensor with a low-cost broadband light source by integrating it with an arrayed waveguide grating spectral filter that divides the sensor's transmission spectrum in multiple wavelength channels and transmits them to spatially separated output ports. Experiments show that this sensor can monitor refractive index changes of watery solutions in real-time with a detection limit (1.6 · 10 −5 RIU ) competitive with more expensive interrogation schemes, indicating its applicability in low-cost label-free biosensing.

An Approach to Ring Resonator Biosensing Assisted by Dielectrophoresis: Design, Simulation and Fabrication

“…Ring resonators with different configurations and geometries have been developed to improve the sensing ability, reduce the impact of production tolerances, and improve the detection limit [ 9 ]. These include the coupling of two linear waveguides to form a single microring, a two-cascade ring resonator (Vernier-cascade silicon photonic label-free biosensor) [ 10 ], and a coupled-resonator optical waveguide (CROW) that is an array of optical cavities, where adjacent cavities are coupled to each other and thereby amplify the response [ 11 ].…”

A Design of a Novel Silicon Photonics Sensor with Ultra-Large Free Spectral Range Based on a Directional Coupler-Assisted Racetrack Resonator (DCARR)

“…For example, Li et al described a cavity that consists of a ring coupled to an asymmetric loop-MZI reflector with FSR = 150 nm [26]. An alternative approach is to couple multiple resonators of different sizes to produce an envelope signal (optical Vernier effect) for which only overlapping resonances are transmitted to a common output [8,27,28]. However, one drawback of these types of devices is their rather large footprint and relatively complex design that is highly susceptible to fabrication tolerance.…”

“…Therefore, to optimise the practical performance of the device, it is necessary to carefully balance the desired S Vernier with the limitations of the detection instrumentation, taking into account the trade-off between sensitivity and dynamic range. Assuming negligible dispersion, the FSR of the envelope (FSR Vernier ) can be expressed as [27]:…”

Optimizing the Limit of Detection of Waveguide-Based Interferometric Biosensor Devices

“…Two different sensing architectures are widely used in photonic biosensing: resonant and interferometric arrangements [21]. Single rings or multiple rings using the Vernier effect have been shown to reach state-of-the-art LODs of around 10−60.166667emRIU [14,16,17,22,23,24]. Unfortunately, to read the sensor signal they require a tunable laser source or a white light source and a spectrum analyzer [23], thereby increasing the complexity of the overall sensing system.…”