Guided mode resonance based phase sensing with spectral interferometry

Abstract

In photonic biosensor designs, the phase-detection methods offer better sensing capabilities and lower detection limits in contrast to other conventional interrogation schemes. However, this class of detection scheme is explored very limitedly for realizing compact biosensing detection schemes. Predominantly, complex experimental setups involving bulk optical components are required for the phase interrogation scheme, which constrains the practical applicability of phase detection apart from the laboratory environment. Here, we present a common-path spectral interferometric technique utilizing a birefringent crystal and spectrometer to evaluate the phase of the guided mode resonance (GMR) signal operating in transmission mode. The common path method offers better stability and constitutes a simple and compact detection modality that can be incorporated into the practical world. A Window Fourier Transform method is implemented to extract the phase of the GMR signal. From the proposed technique, a sensitivity of 103.4 rad/RIU and a limit of detection of 9.8 × 10−5 RIU could be obtained experimentally. This method provides an improved limit of detection as compared to the conventional wavelength interrogation techniques, which also use a spectrometer as the detection system. Hence, this proposed simple and compact detection system enables the realization of highly sensitive portable biosensors.