High-resolution refractometry using phase shifting interferometry based on spatial light modulator and vortex probe

Abstract

We present a spatial light modulator (SLM) based phase shifting interferometry (PSI) using an optical vortex for sensing the refractive index (RI) of liquids. The vortex phase rotates according to the phase shift introduced by a medium, and its rotation angle quantifies the index of refraction of the sample. An interferometer modified with the SLM is designed to obtain reliable results. We experimentally demonstrate the stability of the SLM-based system by measuring interference and phase fluctuation. Experimental results show that the proposed system keeps the fluctuation small. The vortex probe PSI combined with the SLM-based interferometer enables not only detecting extremely small changes in concentration but also precisely measuring the RI with high resolution of ∼10−5 refractive index unit.