Extended Data Fig. 2: Linewidth measurements of the 750-nm and 710-nm Ti:sapphire lasers.
From: Continuous-wave narrow-linewidth vacuum ultraviolet laser source
a, 750-nm Ti:sapphire laser. b, 710-nm Ti:sapphire laser. Both lasers are Pound–Drever–Hall-locked to a 10-cm-long ULE cavity. Each is heterodyned with an optical frequency comb referenced to a ULE-stabilized fibre laser at 1,550 nm (linewidth 0.25(1) Hz). The optical beats are down-mixed to an intermediate frequency within the span of a dynamic signal analyser and the resulting spectra (blue points) are fitted with Lorentzians (blue lines), yielding FWHM linewidths of Δf750 = 1.05(7) Hz and Δf710 = 1.01(9) Hz after subtracting the comb contribution67.
