Optical strain sensor based on diffraction grating and surface plasmon resonance heterodyne interferometer

We designed an optical sensor for measuring a tensile strain by using a diffraction grating and a surface plasmon resonance (SPR) interferometer, and analyzed the periodic nonlinearity effect and the thermal effects in the sensor. As a heterodyne light beam strikes a grating, the +1st order diffraction beam generates and then enters into a SPR apparatus at the resonance angle. A tensile force applied to the grating will introduce a significant phase-difference variation between p- and s-polarizations of the light emerging from SPR apparatus. The variation used to determine the strain can be precisely measured with heterodyne interferometric technique. The feasibility of our method was demonstrated with a measurement resolution of 0.52 mɛ and a sensitivity of 0.58°/mɛ in a dynamic range of 10 mɛ. The sensor provides the advantages of low temperature sensitivity, high stability against air fluctuation, a simple structure, rapid measurement, and straightforward operation.

► We designed an optical strain sensor using a diffraction grating and SPR heterodyne interferometry.
► This study derived the equations of the phase difference variation versus the tensile strain.
► The sensor has merits of low temperature sensitivity, high stability, a simple structure, rapid measurement, and easy operation.