Optimization and prospects of the use of antireflection optical films in biomedicine

Abstract

The work is devoted to the optimization of the structure of a multilayer anti-reflective film with good integral optical properties in a wide range of angles of incidence and wavelengths of the infrared range, coinciding with the absorption of CO2, and for both types of polarization of the incident wave. The optimization is performed on the basis of the initial solution of the problem, which is adjusted to a quarter-wave optical thickness of each layer(SiO2, SiO, SiO1<x<2, Si), where the optical thickness is chosen from the condition of maximum sensitivity to the absorption spectrum of carbon dioxide (CO2). The matrix method is used to determine the integral reflection coefficient. Next, the thickness of the layers of the system is optimized by finding the global minimum of the function that determines the total amount of reflected radiation in a given range of wavelengths and angles of incidence of radiation. It is shown that by means of statistical modelling it is possible to determine the thickness of the film layers, which provides a systematic improvement in the value of the integral reflection coefficient. It is also shown that by means of statistical modelling it is indeed possible to obtain an optimized film structure, despite a small improvement in the integral reflection coefficient (less than 1%). Therefore, the developed analysis method has important practical significance for the analysis and detection of absorption effects of optical radiation of non-interference origin. The results of the research are also compared with studies using the Swanepoel method and published in literary sources. The obtained results are of practical interest in biomedical applications: biocompatible thin films of implanted organs, optical sensors for medical diagnostic systems, since in biological structures non-interference absorption effects of the optical range have a systematic and clearly expressed appearance.