K. Stahrenberg, Th. Herrmann, K. Wilmers, N. Esser, W. Richter, and M. J. G. Lee. Optical properties of copper and silver in the energy range 2.5-9.0 eV, Phys Rev. B64, 115111 (2001) (Numerical data kindly provided by Prof. Dr. Norbert Esser)
Copper (Cu) is a highly versatile transition metal with excellent electrical and thermal conductivity. While its primary applications span electrical wiring, plumbing, and various industrial machinery, it also finds specialized uses in optics. Notably, polished, bare copper is often the material of choice for high-power infrared mirrors, including those used in CO2 lasers, due to its high reflectivity in the infrared spectrum and exceptional thermal resilience. The metal's malleability and corrosion resistance further allow it to be shaped into intricate forms, making it invaluable across a range of industries. Whether in general construction or specific niches like high-power optical components, copper's multifaceted properties make it a material of critical importance.