Unveiling out-of-loop attosecond timing jitter precision in Ti:sapphire mode-locked lasers with an optical heterodyne technique.

The out-of-loop timing jitter exhibited in free-running Ti:sapphire mode-locked lasers with attosecond resolution is demonstrated using an optical heterodyne technique. To assess the feasibility of the experiment and discrimination signal properties, numerical simulations were conducted for Ti:sapphire mode-locked lasers. For accurately characterizing the genuine phase noise exhibited by Ti:sapphire mode-locked lasers, out-of-loop measurements were conducted, and a straightforward yet improved optical heterodyne setup was employed, allowing simultaneous low-bandwidth locking and out-of-loop timing jitter measurements with two Ti:sapphire mode-locked lasers. The out-of-loop phase noise floor for a single mode-locked laser reaches -203.47 / , assuming a 10 GHz carrier frequency. Additionally, the out-of-loop integrated timing jitter is 11.9 from 10 kHz to the Nyquist frequency (50 ).