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-decade of Fourier frequency from mHz to tens 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.

Frequency comb-based microwave transfer over fiber with $7 times 10^{-19}$ instability using fiber-loop optical-microwave phase detectors

We demonstrate a remote microwave/radio-frequency (RF) transfer technique based on the stabilization of a fiber link using a fiber-loop optical-microwave phase detector (FLOM-PD). This method compensates for the excess phase fluctuations introduced in fiber transfer by direct phase comparison between the optical pulse train reflected from the remote site and the local microwave/RF signal using the FLOM-PD. This enables sub-fs resolution and long-term stable link stabilization while having wide timing detection range and less demand in fiber dispersion compensation. The demonstrated relative frequency instability between 2.856-GHz RF oscillators separated by a 2.3-km fiber link is $7.6 times 10^{-18}$ and $6.5 times 10^{-19}$ at 1000 s and 82500 s averaging time, respectively.

Sub-100-as timing jitter optical pulse trains from mode-locked Er-fiber lasers

We demonstrate sub-100-attosecond timing jitter optical pulse trains generated from free-running, 77.6-MHz repetition-rate, mode-locked Er-fiber lasers. At -0.002(pm0.001) ps2 net cavity dispersion, the rms timing jitter is 70 as (224 as) integrated from 10 kHz (1 kHz) to 38.8 MHz offset frequency, when measured by a 24-as-resolution balanced optical cross-correlator. To our knowledge, this result corresponds to the lowest rms timing jitter measured from any mode-locked fiber lasers so far. The measured result also agrees fairly well with the Namiki-Haus analytic model of quantum-limited timing jitter in stretched-pulse fiber lasers.

Timing jitter optimization of mode-locked Yb-fiber lasers toward the attosecond regime

We demonstrate ultra-low timing jitter optical pulse trains from free- running, 80 MHz repetition rate, mode-locked Yb-fiber lasers. Timing jitter of various mode-locking conditions at close-to-zero intra-cavity dispersion (-0.004 to +0.002 ps2 range at 1040 nm center wavelength) is characterized using a sub-20-attosecond-resolution balanced optical cross-correlation method. The measured lowest rms timing jitter is 175 attoseconds when integrated from 10 kHz to 40 MHz (Nyquist frequency) offset frequency range, which corresponds to the record-low timing jitter from free-running mode-locked fiber lasers so far. We also experimentally found the mode-locking conditions of fiber lasers where both ultra-low timing jitter and relative intensity noise can be achieved.