Noise characterization of femtosecond color-center lasers

We used power-spectrum techniques to measure both amplitude noise and timing jitter of two femtosecond colorcenter lasers in the near infrared: a passively mode-locked laser and an additive-pulse mode-locked laser. The cw pumped passively mode-locked color-center laser showed better noise performance than the feedback-controlled, much more complex additive-pulse mode-locked color-center laser. For both laser systems, we observed unexpected drastic increases of amplitude noise under certain operation conditions. In the low-noise operation regime, the amplitude noise of the passively mode-locked color-center laser is entirely dominated by its pump laser, whereas the additive-pulse mode-locked laser exhibits >10 dB of excess noise up to 200 kHz and tended to break up in the subhertz regime. The timing jitter for both lasers was approximately 9 psec rms for jitter rates above 130 Hz.