Compact and bench-top common-path interferometric biosensor utilizing guided mode resonance phase enhancement

The early detection and diagnosis of diseases are of paramount importance for effective healthcare outcomes. Serum albumin is an important biomarker for many diseases. A reduction in albumin can be noted in various diseases, rendering it an important marker for assessing disease progression and treatment efficacy. To get accurate readings of these biomarker levels, we need methods that are very sensitive, reliable, quick, and non-invasive. Optical phase detection techniques exhibit high sensitivity, convenient readout strategies, and low limit of detection (LOD) in comparison to other detection methods. Here, we demonstrate a new phase detection mechanism employing a Fresnel biprism in conjunction with resonantly enhanced phase sensitivity achieved by using guided mode resonance (GMR). These elements are combined into a compact and bench-top common-path phase-detection system that can be realized with very few low-cost components. The common-path configuration effectively mitigates mechanical vibrations typically associated with two-beam interferometry used for phase detection. To demonstrate the capability of our approach, we designed and fabricated a GMR-based instrument and used it to detect bovine serum albumin (BSA) at different concentrations. The stability of the setup was instrumental in detecting BSA concentrations as low as 1 pg/mL.