Loss-Induced Resonant Refractive Index Sensing using Total Internal Reflection Phase Shift

Refractometry has a variety of applications in chemistry, biotechnology, or food industry. A number of sensor systems are available to analyze the refractive index of liquid solutions or even biological tissue. We present a novel technique that aims at recording local distributions of refractive indices. The approach relies on the phase shift upon total internal reflection (TIR) and uses an extremely short Fabry-Pérot microcavity of less than 3 μm effective length as the key element to precisely measure refractive indices at less than 100 μm spatial resolution.