Active-synchronization between two femtosecond lasers based on phase locked loops

We demonstrate a reduction of the timing jitter between two actively synchronized Ti: sapphire lasers by using a combination of three phase looked loops(PLLs). The main PLL works for primary synchronization, the second one maintains long-term stability and the third one (an optical PLL) increases the precision. The PLLs permit the achievement of timing jitter less than 30fs measured in 10 seconds, while the laser pulse width is about 100fs.