Free-running quantum dot SESAM modelocked VECSEL with record-low timing jitter

Our laser is an InGaAs quantum well VECSEL operating at 953 nm passively modelocked with a quantum dot SESAM. It generates 4.6-ps pulses with 2 GHz repetition rate and 50 mW average output power. High mechanical stability is achieved by fixing all optical elements including the pump diode in a metallic housing avoiding air currents and reducing vibrations. This laser is free-running, the cavity length is not actively stabilized. Only the VECSEL heat sink is maintained at 15°C, while pump diode temperature and base plate temperature are not stabilized. The phase noise of the free-running laser integrated over a bandwidth from 100 Hz to 1 MHz corresponds to an RMS timing jitter of ≈212 fs, which is lower than previously obtained for modelocked VECSELs. Our measurements confirm that well-designed OP-VECSELs can achieve comparable low-noise performance as standard ion-doped solid-state lasers.