Diagnostics of Thin Gradient Dielectric Coatings by Surface Plasmon Resonance Microscopy and Ghost Imaging

The application of surface plasmon resonance microscopy for the time-continuous nondestructive control of thin dielectric coatings during their fabrication is considered. The high sensitivity of the method, in comparison with other photometric methods, and time-continuous optical control makes it possible to correctly restore the thickness profiles and optical constants for multilayer and gradient dielectric coatings. Adaptation of the ghost-imaging method to surface plasmon resonance microscopy makes it possible to measure the reflection coefficients locally for each surface point. It makes it possible to restore the spatial distribution of optical constants for planar optical elements. The operation of the method is described by the example of the Luneburg plasmon-lens model. One of the possible schemes of implementation of the proposed method in production (for a magnetron-sputtering unit) is presented. The superiority in the sensitivity of the surface plasmon resonance method over spectroreflectometry by 2 orders of magnitude in the case of the optical characterization of ultrathin dielectric films during their growth in thickness and in the case of the mutual diffusion of dielectric layers is demonstrated by examples. The source codes in Python of the numerical results are published in GitHub repository. The described approach of optical control is applicable both in the visible and infrared ranges of the electromagnetic spectrum.