Fabry-Perot interferometer with picometer resolution referenced to an optical frequency comb

A picometer resolution Fabry-Perot (F-P) interferometer is proposed. The Pound-Drever-Hall locking scheme is employed to lock the frequency of a tracking external cavity diode laser (ECDL) to the resonance of a F-P cavity. The frequency change of ECDL induced by the probe mirror displacement is measured using an optical frequency comb (OFC). Therefore, the measurement result of the F-P interferometer is traceable to the radio frequency reference of the OFC. Experimentally, we demonstrate that the displacement resolution of 0.46 pm at 80 ms averaging time is achieved in our F-P interferometer and the uncertainty is 1.2 nm at the displacement of 1μm. One application example of the F-P interferometer is presented to measure the hysteresis nonlinearity of the piezoelectric transducer attached to the probe mirror. The hysteresis nonlinearity observed is about 6% over the displacement of 700 nm.