We review the most recent progress in ultralow-noise mode-locked fiber lasers and fiber-based frequency-comb sources. With the rapid progress in theory, measurement, and control of noise in passively mode-locked fiber lasers, we have reached the point where the residual carrier–envelope-offset phase jitter (when stabilized) and pulse timing jitter performance of such laser sources can be fully optimized to the unprecedented levels of attoseconds regime. In this paper, first, major principles in building such low-noise passively mode-locked fiber lasers are reviewed. We then define noise in mode-locked fiber lasers and present the basic theoretical and numerical framework for analyzing the noise in mode-locked fiber lasers. More detailed discussions on theory, measurement methods, state-of-the-art performances, and stabilization methods of intensity noise, timing jitter, and comb-line frequency noise follow. Finally, we overview today’s most representative applications of such ultralow-noise mode-locked fiber lasers and frequency-comb sources. As an already powerful tool for various high-precision applications, ultralow-noise mode-locked fiber lasers will keep finding more exciting applications in optical science and photonic technology in the coming years.

Ultrafast fiber lasers exhibit high broadband gain per pass, superior thermo-optical properties, and excellent beam quality, making them very suitable for practical use. For simplicity and efficiency, advanced mode-locked oscillator designs which can compete with the amplifier systems are always favorable. Here, we demonstrate a high-peak-power Mamyshev oscillator based on single-polarization, large-mode-area photonic crystal fibers. Using properly arranged filters, the fiber oscillator directly emits pulses with 9 W average power at 8 MHz repetition rate, corresponding to a single-pulse energy exceeding 1 μJ. The pulses are dechirped to 41 fs outside the cavity, leading to a record oscillator peak power as high as 13 MW. With such unprecedented performance, the proposed single-stage oscillator should be very attractive for various applications.

We demonstrate dual-comb spectroscopy in the vicinity of 2 µm wavelength based on a single dual-wavelength dual-comb Thulium-doped fiber laser. The shared laser cavity ensures passively maintained mutual coherence between the two combs due to common mode environmental noise rejection. In a proof-of-principle experiment, the absorption characteristics caused by the water in the optical path that composes the dual-comb spectrometer are measured. The retrieved spectral positions of the water absorption dips match with the HITRAN database.

Optics InfoBase is the Optical Society's online library for flagship journals, partnered and copublished journals, and recent proceedings from OSA conferences.

We demonstrate sub-$100\text{-}\mathrm{as}$ timing jitter optical pulse trains generated from free-running, $77.6\mathrm{MHz}$ repetition-rate, mode-locked Er-fiber lasers. At $-0.002(\pm 0.001){\mathrm{ps}}^2$ net cavity dispersion, the rms timing jitter is $70\mathrm{as}$ ($224\mathrm{as}$) integrated from $10\mathrm{kHz}$ ($1\mathrm{kHz}$) to $38.8\mathrm{MHz}$ offset frequency, when measured by a $24\mathrm{as}$ 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.

We demonstrate an all polarization-maintaining (PM) fiber based dual-wavelength mode-locked Er-fiber laser. A nonlinear amplifying loop mirror (NALM) with an intracavity nonreciprocal phase shifter is used for self-started mode-locking. A short segment of PM fiber is angle-spliced to the NALM, functioning as a PM Sagnac loop filter, thus enabling dual-wavelength mode-locking. The wavelength separation is solely determined by the angle-spliced PM fiber length. Stable dual-wavelength mode-locking operation is switchable between 1570/1581 nm and 1581/1594 nm. The two-color pulse trains oscillating in the same cavity have an inherent offset repetition rate of ~1 kHz owing to cavity dispersion, allowing future high precision dual-comb applications with a simple and robust configuration.