Solid and air-spaced etalons come in various shapes
Solid and air-spaced etalons in various shapes are available at customer-defined wavelengths from 190 nm to 2 µm and surface accuracy >λ/300 P-V. They are used in telecommunications, lasers and spectroscopy, and in precision tunable Fabry-Pérot etalons. Standard materials include UV-grade silica, silicon, and germanium.
Optical Surfaces
Kenley, U.K.