A figure of merit for a Fabry-Perot cavity or etalon, set mainly by mirror reflectivity and loss. With 99 percent mirrors finesse is about 300; supermirrors with losses of a few parts per million reach over 100,000. High finesse gives narrow transmission peaks for frequency references, cavity ring-down and laser stabilization, but makes the cavity very sensitive to alignment and contamination.
Finesse dropped from 20,000 to 6,000 overnight, something landed on the mirrors, so we're cleaning in the flow hood.
Also heard as
- cavity finesse
Related terms
Free spectral range
The frequency spacing between neighboring resonances of a laser cavity, etalon or interferometer.
Etalon
A pair of parallel reflecting surfaces that transmits a comb of sharp frequency peaks, used to select or measure wavelengths.
Linewidth
The spectral width of a single-frequency laser's output, usually given in Hz, kHz or MHz at half maximum.
Resonator
The arrangement of mirrors that sends light back and forth through the gain medium to build up laser oscillation.