Figure 2
From: Gravity measurements below 10−9 g with a transportable absolute quantum gravimeter
Laser linewidth (left) and long-term frequency stability measurements (right). We make a beatnote between the laser of the gravimeter and a similar independent laser. A Lorentzian fit of the tails of the beatnote gives a linewidth of less than 12 kHz for each laser. By recording the frequency of the beatnote over time on a frequency counter, we can estimate the long-term frequency stability of the lasers. Here, the standard deviation over four days is 27 kHz, and no significant drift is visible on the measurement.
