Experimental implementation of a spectral refractive index sensor based on a reflection interferometer

Experimental study of the sensor in the Kretschmann optical scheme, in which the sensitive element is a reflection interferometer (RI) for the oblique incidence of light, is presented for the first time. A brief theory of RI is given. The experimental sample was used to measure the refractive index of the residual atmosphere in a vacuum chamber during its pumping. The high Q-factor of the RI resonator made it possible to obtain a fairly narrow spectral maximum with a width of 1.7 nm. The spectral sensitivity of the sensor was 1000 nm/RIU and the quality parameter was 529 RIU$^{-1}$, it was also demonstrated that resolution of 6.5 $\cdot$ 10$^{-8}$ RIU can be achieved. Proposals for further improvement of the sensor characteristics are formulated.