See https://refractiveindex.info/about
refractiveindex.info Database
This comprehensive database of optical constants was initiated and has been maintained by Mikhail Polyanskiy since 2008. It is a compilation of data from publicly available sources such as scientific journal articles and material datasheets published by manufacturers. Numerous researchers have contributed to the refractiveindex.info database by providing numerical data, reporting bugs, and suggesting improvements.
The database is made freely available under the CC0 1.0 Universal Public Domain Dedication. This means you are free to use, modify, and distribute its content without any restrictions, even for commercial purposes, no permission required.
The refractiveindex.info database is organized as a library of YAML files. This file format was chosen for its simplicity, clarity, and human readability.
RefractiveIndex.INFO Website
The RefractiveIndex.INFO website serves as a user interface to the refractiveindex.info database, offering straightforward access to the data and basic calculations such as absorption, Fresnel reflection, and Brewster angle. Mikhail Polyanskiy is the owner and maintainer of the website.
Using the RefractiveIndex.INFO website is not a requirement for accessing the refractiveindex.info database. Alternative web-based interfaces, Python scripts, and other methods (including direct reading of the YAML files) can be used.