GRATING-COUPLED SURFACE-PLASMON FOR MEASURING THE REFRACTIVE-INDEX OF A LIQUID SAMPLE

We propose a technique for measuring the refractive index of a liquid sample through the use of a grating-coupled surface plasmon. The surface plasmon is excited on the metallic grating by an incident optical beam. The liquid sample is placed in contact with the grating, and its refractive index is determined from the dependence of the plasmon excitation angle on the refractive index value. The effects of the grating groove pitch and depth on the measured value of the refractive index are analysed using the mode-matching method. Experimental results are presented for water and ethanol samples.