Fig. 2: Characterization of the overall frequency reference chain.
From: Absolute frequency metrology of buffer-gas-cooled molecular spectra at 1 kHz accuracy level
Characterization of the ECDL → BGC-HFC → OFCS → Rb/GPS lock chain, as derived by the fast Fourier transform (FFT) of the servo (mFALC110) error/correction signal. It is evident the excess noise due to the PT operation (fairly mitigated by the introduction of the Vulcuren elements), which in particular amplifies a structural (i.e., already present at room temperature) resonance at 100 Hz together with its second harmonic.
