The transmission of an ctalon as a function of wavclength. Ahigh-finessc ctalon (red linę) shows sharper peaks and lower transmission minima than a low-finesse etalon (blue).
The maximuni reflcctivity is given by:
Rmax 1
1
l + F
and this occurs when the path-lcngth diffcrence is equal to half an odd multiple of the wavelcngth.