Spectral measurement of the noise in continuous-wave mode-locked laser pulses

A theoretical analysis of the noise of a periodic optical pulse train is presented. It is shown that the amplitude fluctuation, the pulsewidth fluctuation, the pulse timing jitter, and the cross correlations between any two of these three noise parameters can be separately quantified by comparing the noise power spectra of the fundamental pulses and those of the second-harmonic pulses. The noise characteristics of an actively mode-locked Nd:YLF laser are presented to demonstrate this technique.