Phase-interrogated surface plasmon resonance sensor based on laser feedback interferometry

This work reports a phase-interrogated surface plasmon resonance sensor based on a laser feedback interferometer to detect a small refractive index change. The laser feedback interferometer technique is introduced to demonstrate the sensing technique's performance, which offers several inherent advantages, such as compact, optically self-aligned, and high accuracy measurement. Moreover, this technique doubles the interrogating light beam propagation to the solution under the test, leading to an improvement of intrinsic sensitivity measurement up to two-fold. The proposed technique was characterized, and the performance was compared to another phase-interrogated surface plasmon resonance (SPR) based on the Mach-Zehnder interferometer. Laser feedback interferometer SPR has shown significant improvement to the performance parameter under test, namely sensitivity, drift, repeatability, and resolution.