Gires-Tournois_interferometer
In optics, a Gires–Tournois etalon (also known as Gires–Tournois interferometer) is a transparent plate with two reflecting surfaces, one of which has very high reflectivity, ideally unity. Due to multiple-beam interference, light incident on a Gires–Tournois etalon is (almost) completely reflected, but has an effective phase shift that depends strongly on the wavelength of the light.
The complex amplitude reflectivity of a Gires–Tournois etalon is given by
where r1 is the complex amplitude reflectivity of the first surface,
- n is the index of refraction of the plate
- t is the thickness of the plate
- θt is the angle of refraction the light makes within the plate, and
- λ is the wavelength of the light in vacuum.