Etalons perform like a Fabry-Pérot interferometer and are extremely plane-parallel substrates (//<1") of defined thickness. Depending on the application, the two side surfaces are identically coated with a partially reflecting mirror. The distance between two transmission maxima depends on the etalon thickness. Depending on the freely selectable reflectance, the resolving power can also be influenced.

LAYERTEC offers etalons e.g. made of fused silica, crystalline quartz, CaF2, undoped YAG, BK10 with customer specific diameters. Fabrication down to 50 µm thickness and parallelism <1 arcsec is possible depending on the diameter. We are able to adjust the etalon thickness within the periodicity down to 10 nm.

By a fine angle adjustment an etalon can be adjusted to the desired transmission wavelength. Conversely, the function of an etalon is disturbed by a beam that is not plane-parallel.

Fig. 1   Geometry of a Fabry-Perot cavity and illustration of standing waves in the case of resonance
Fig. 2   Calculated with L = 1 cm for different finesse values F