Ultrasensitive Optical Refractive Index Detection of NaCl and Alcohol Solutions Based on Weak Value Amplification

Abstract

An ultrasensitive surface plasmon resonance (SPR) refractive index detection scheme based on weak value amplification is presented. Extremely low refractive index change (9.8 × 10−7 RIU) of sodium chloride solution was readily measurable, with a resolution of 1.3 × 10−7 RIU, a nearly three orders of magnitude increase in sensitivity over conventional SPR index-sensors via intensity interrogation. Preliminary measurement of refractive index change of alcohol solution demonstrated a minimum of 4.0 × 10−6 RIU with a resolution of 3.7 × 10−7 RIU, better than those obtained through wavelength-modulated heterodyne interferometry (with a resolution of 1.5 × 10−6 RIU). The system is highly stable, having a simple and compact configuration, lending to easy and repeatable operation in standard ambient environment.