Inversion of Optical Constants from Reflectance Curve Measurements of Optical Thin Films

This paper introduces a method for determining optical constants (including thickness and refractive index) by measuring the reflectance curve of optical thin films. The fundamental principle involves measuring the reflectance characteristics of optical films and inversely calculating their optical parameters from the obtained data. Specifically, the methodology employs specialized instrumentation to acquire precise reflectance curves, followed by numerical optimization algorithms (such as genetic algorithms or gradient descent methods) to solve the inverse problem. Implementation typically involves constructing a theoretical reflectance model based on the transfer matrix method, which simulates light propagation through multilayer structures. The inverse calculation process minimizes the difference between measured and simulated reflectance data through iterative fitting procedures. Key functions in the implementation include spectral data preprocessing, merit function calculation, and parameter space exploration. This approach not only provides accurate determination of optical constants but also demonstrates high stability and reliability, making it widely applicable in scientific research and engineering applications. In summary, this method offers researchers and engineers a robust tool for characterizing optical thin films, thereby enhancing the understanding of their properties and practical applications.