Noise of the stretched pulse fiber laser. II. Experiments

For pt.I see ibid., p.649, 1997. The noise characteristics of the stretched pulse fiber ring laser are determined from the power spectrum of the current of a detector illuminated by the output pulse train. Amplitude fluctuations as low as 0.05% of the pulse energy and jitter <80 fs (measurement time=0.09 s) are obtained with no external stabilization. These are the lowest noise levels reported to date for a passively mode-locked laser. The experimental results are compared with the noise theory of the companion paper. Good agreement is obtained between theory and experiment. Comparison with theory also shows that the jitter at frequencies higher than 60 Hz is due to amplified spontaneous emission (quantum) fluctuations when the measurement time is on the order of 0.1 s.