Attosecond-resolution timing jitter characterization of free-running mode-locked lasers.

Timing jitter characterization of optical pulse trains from free-running mode-locked lasers with attosecond resolution is demonstrated using balanced optical cross correlation in the timing detector and the timing delay configurations. In the timing detector configuration, the balanced cross correlation between two mode-locked lasers synchronized by a low-bandwidth phase-locked loop is used to measure the timing jitter spectral density outside the locking bandwidth. In addition, the timing delay configuration using a 325 m long timing-stabilized fiber link enables the characterization of timing jitter faster than the delay time. The limitation set by shot noise in this configuration is 2.2 x 10(-8) fs(2)/Hz corresponding to 470 as in 10 MHz bandwidth.