Analytical Description of the Spectral Characteristics of a Refractive Index Sensor Based on a Reflection Interferometer

摘要

For the first time, analytical formulas are presented that describe the spectral characteristics of a sensor based on a reflection interferometer for oblique incidence of light in the Kretschmann's optical scheme. This sensor is designed to measure the refractive index of an analytical medium (liquid, gas) due to the effect of total internal reflection in a structure based on a metal-dielectric multilayer coating. The parameters of a thin metal film included in the structure are determined, which are necessary to optimize the spectral profile of the sensor, which have a spectral maximum with a variable width. As a dielectric coating, quarter-wave layers are used for oblique incidence of light. Analytical dependences of the sensor characteristics on polarization are given: resolution, sensitivity and contrast, as well as the quality parameter. Theoretically, the quality parameter of the sensor can have infinitely high values for both polarizations, but in practice it is limited by losses in the layers of the structure. It is shown that it is more advantageous to use S-polarization due to the higher Q-factor of the resonator in the sensor structure with the same number of dielectric layers. A method for fabricating a sensor structure with optical control in the process of vacuum deposition is proposed.