Characterization of timing jitter spectra in free-running mode-locked lasers with 340  dB dynamic range over 10 decades of Fourier frequency.

We demonstrate a method that enables accurate timing jitter spectral-density characterization of free-running mode-locked laser oscillators over more than 10 decades of Fourier frequency from mHz to tens of MHz range. The method is based on analyzing both the input voltage noise to the slave laser and the output voltage noise from the balanced optical cross-correlator (BOC), when two mode-locked lasers are synchronized in repetition rate by the BOC. As a demonstration experiment, timing jitter spectrum of a free-running mode-locked Er-fiber laser with a dynamic range of >340  dB is measured over Fourier frequency ranging from 1 mHz to 38.5 MHz (Nyquist frequency). The demonstrated method can resolve different noise mechanisms that cause specific jitter characteristics in free-running mode-locked laser oscillators for a vast range of time scales from <100  ns to >1000  s.