Concentration monitoring through a refractive index compass based on metasurface

Abstract

We have designed a directly-displayed refractive index detection chip based on rotating metal nanopillar arrays. When environments fluctuate, it can focus the detection signal on different directions as designed. This refractive index compass can be easily attached to conventional portable devices due to its compact structure, and has a wide adjustable working range. By utilizing multiple phase information contained in a single metasurface, the environmental refractive index on surface or solution concentration can be accurately determined by observing the position and color of the focal point under dual wavelength common incidence.