This Review explains the concept of dissipative solitons and their application to high-energy mode-locked fibre laser cavities. Dynamics and effects such as dissipative soliton ‘explosions’ and ‘rain’ are summarized, and an outlook of the field is also provided.

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Dissipative solitons for mode-locked lasers

Dual-comb spectroscopy is an emerging new spectroscopic tool that exploits the frequency resolution, frequency accuracy, broad bandwidth, and brightness of frequency combs for ultrahigh-resolution, high-sensitivity broadband spectroscopy. By using two coherent frequency combs, dual-comb spectroscopy allows a sample’s spectral response to be measured on a comb tooth-by-tooth basis rapidly and without the size constraints or instrument response limitations of conventional spectrometers. This review describes dual-comb spectroscopy and summarizes the current state of the art. As frequency comb technology progresses, dual-comb spectroscopy will continue to mature and could surpass conventional broadband spectroscopy for a wide range of laboratory and field applications.

Dual-comb spectroscopy

Self-similar propagation of ultrashort, parabolic pulses in a laser resonator is observed theoretically and experimentally. This constitutes a new type of pulse shaping in mode-locked lasers: in contrast to the well-known static (solitonlike) and breathing (dispersion-managed soliton) pulse evolutions, asymptotic solutions to the nonlinear wave equation that governs pulse propagation in most of the laser cavity are observed. Stable self-similar pulses exist with energies much greater than can be tolerated in solitonlike pulse shaping, and this has implications for practical lasers.

https://arxiv.org/pdf/physics/0402013.pdf

Self-similar evolution of parabolic pulses in a laser.

A modelocked fiber laser is designed to have strong pulse-shaping based on spectral filtering of a highly-chirped pulse in the laser cavity. The laser generates femtosecond pulses without a dispersive delay line or anomalous dispersion in the cavity.

All-normal-dispersion femtosecond fiber laser

The generation and stable propagation of ultrashort optical pulses tend to be limited by accumulation of excessive nonlinear phase shifts. The limitations are particularly challenging in fiber-based devices, and as a result, short-pulse fiber lasers have lagged behind bulk solid-state lasers in performance. This article will review several new modes of pulse formation and propagation in fiber lasers. These modes exist with large normal cavity dispersion, and so are qualitatively distinct from the soliton-like processes that have been exploited effectively in modern femtosecond lasers but which are also quite limiting. Self-similar evolution can stabilize high-energy pulses in fiber lasers, and this leads to order-of-magnitude increases in performance: fiber lasers that generate 10 nJ pulses of 100 fs duration are now possible. Pulse-shaping based on spectral filtering of a phase-modulated pulse yields similar performance, from lasers that have no intracavity dispersion control. These new modes feature highly-chirped pulses in the laser cavity, and a theoretical framework offers the possibility of unifying our view of normal-dispersion femtosecond lasers. Instruments based on these new pulse-shaping mechanisms offer performance that is comparable to that of solid-state lasers but with the major practical advantages of fiber.

High-energy femtosecond fiber lasers based on pulse propagation at normal dispersion

We report the generation of 6-nJ chirped pulses from a mode-locked Yb fiber laser at 1.03 μm . A linear anomalous-dispersion segment suppresses wave-breaking effects of solitonlike pulse shaping at high energies. The dechirped pulse duration is 50 fs, and the energy is 5 nJ. This laser produces twice the pulse energy and average power, and approximately five times the peak power, of the previous best mode-locked fiber laser. It is to our knowledge the first fiber laser that directly offers performance similar to that of solid-state lasers such as Ti:sapphire.

W. G. Clark

Papers

Self-similar evolution of parabolic pulses in a laser.

Generation of 50-fs, 5-nJ pulses at 1.03 μm from a wave-breaking-free fiber laser