Fig. 4: Long-term stability characterisation of a 1.965 GHz beatnote generated by the DFG setup.
From: Frequency stable and low phase noise THz synthesis for precision spectroscopy
a Raw measurement of the Las1 optical frequency drift. b Experimental difference frequency beatnote drift (blue). Calculated beatnote drift (orange trace) applying a scaling factor of 1.015 × 10−5 to the Las1 drift plotted in panel a, this trace is offset by 10 Hz for better readability. See text for details. c Overlapping Allan deviation plot of the experimental difference frequency data from panel b showing sub-Hz level stability on short time and 0.17 mHz/s long-term drift.
