Sub-60-fs Timing Jitter of a SESAM Modelocked VECSEL

We present noise measurements of a pulse train emitted from an actively stabilized semiconductor-saturable-absorber-mirror (SESAM) modelocked vertical external cavity surface emitting laser (VECSEL). The laser generated 6-ps pulses with 2-GHz pulse-repetition rate and 40-mW average output power. The repetition rate was phase locked to a reference source using a piezo actuator. The timing phase noise power spectral density of the laser output was detected with a highly linear photodiode and measured with a signal source analyzer. The resulting RMS timing jitter integrated over an offset frequency range from 1 Hz to 100 MHz gives a value of below 60 fs, lower than previous modelocked VECSELs and comparable with the noise performance of ion-doped solid-state lasers. The RMS amplitude noise was below 0.4% (1 Hz to 40 MHz) and not influenced by the timing phase stabilization.