Editing Fabry–Pérot interferometer (section)

=== Spectroscopy ===

Fabry–Pérot etalons can be used to prolong the interaction length in [[laser absorption spectrometry]], particularly [[cavity ring-down spectroscopy|cavity ring-down]], techniques. An etalon of increasing thickness can be used as a linear variable optical filter to achieve [[spectroscopy]]. It can be made incredibly small using thin films of nanometer thicknesses.<ref>{{cite journal |last1=Vasireddy |first1=S |title=A general-purpose spectroscopic camera for single-board computers |journal=Optik |date=May 2024 |volume=302 |pages=171710 |doi=10.1016/j.ijleo.2024.171710 |url=https://www.sciencedirect.com/science/article/pii/S0030402624001086|url-access=subscription }}</ref>

A Fabry–Pérot etalon can be used to make a [[spectrometer]] capable of observing the [[Zeeman effect]], where the [[spectral lines]] are far too close together to distinguish with a normal spectrometer.