Two mode-locked Ti:sapphire lasers were synchronized with different kinds of phase-locked loops. Conventional phase-locked loop (EPLL) systems employ an electrical device known as a double balanced mixer for phase comparison. However, a novel phase-locked loop in our system employs an optical up-converted signal (OPLL). When two lasers were synchronized with the EPLL, the up-converted signal of two lasers was measured and the relative timing jitter for 1 ms was estimated to be longer than 430 fs. When two lasers were synchronized with the OPLL, the crosscorrelation of two lasers could be measured for the small relative timing jitter. The timing jitter of two lasers for 1.8 s was 28 fs. The holding time of the OPLL was 60 minutes.
© 2001 Optical Society of AmericaPDF Article