Investigation of Sodium D Lines with a Fabry-Pérot Etalon

Fabry-Pérot etalons are widely used in laser resonators and spectroscopy for sensitive wavelength filtering. Typically, they are composed of two high-reflective (HR) coated surfaces with air or glass in between. In this example, an optical metrology system with a silica spaced etalon is set up to measure the sodium D lines in VirtualLab Fusion. With the non-sequential field tracing technique, the interference due to multiple reflections in the etalon is fully considered, and the influence from the reflectance of the applied coatings on the fringe contrast is investigated.