Resonant two-beam interferometric sensor independent of intracavity losses
Résumé
We study a resonant interferometric sensor with two cavity eigenstates. The finesse associated to one eigenstate is significantly lower than the empty cavity value, because of the presence of a lossy intracavity sample. We show theoretically that the sensitivity of the interferometer only depends on the empty cavity finesse when the low-finesse eigenfrequency is locked to resonance. This is experimentally demonstrated and a resolution of 60 pm is reported. Our method can be applied to any resonant two-beam interferometer.