Bose-Einstein condensation (BEC) has been observed in a dilute gas of sodium atoms. A Bose-Einstein condensate consists of a macroscopic population of the ground state of the system, and is a coherent state of matter. In an ideal gas, this phase transition is purely quantum-statistical. The study of BEC in weakly interacting systems which can be controlled and observed with precision holds the promise of revealing new macroscopic quantum phenomena that can be understood from first principles.

Bose-Einstein condensation in a gas of sodium atoms

The rise in output power from rare-earth-doped fiber sources over the past decade, via the use of cladding-pumped fiber architectures, has been dramatic, leading to a range of fiber-based devices with outstanding performance in terms of output power, beam quality, overall efficiency, and flexibility with regard to operating wavelength and radiation format. This success in the high-power arena is largely due to the fiber’s geometry, which provides considerable resilience to the effects of heat generation in the core, and facilitates efficient conversion from relatively low-brightness diode pump radiation to high-brightness laser output. In this paper we review the current state of the art in terms of continuous-wave and pulsed performance of ytterbium-doped fiber lasers, the current fiber gain medium of choice, and by far the most developed in terms of high-power performance. We then review the current status and challenges of extending the technology to other rare-earth dopants and associated wavelengths of operation. Throughout we identify the key factors currently limiting fiber laser performance in different operating regimes—in particular thermal management, optical nonlinearity, and damage. Finally, we speculate as to the likely developments in pump laser technology, fiber design and fabrication, architectural approaches, and functionality that lie ahead in the coming decade and the implications they have on fiber laser performance and industrial/scientific adoption.

High power fiber lasers: current status and future perspectives [Invited]

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.

Ultrafast fibre lasers are an important optical system with industrial, medical and purely scientific applications. Essential components and the operation regimes of ultrafast fibre laser systems are reviewed, as are their use in various applications.

Ultrafast fibre lasers

Nanotubes and graphene have emerged as promising materials for use in ultrafast fibre lasers. Their unique electrical and optical properties enable them to be used as saturable absorbers that have fast responses and broadband operation and that can be easily integrated in fibre lasers.

Nanotube and graphene saturable absorbers for fibre lasers

A new design scheme for a comb-like dispersion decreasing fibre (DDF) has been implemented in a two stage cascaded DDF similariton compression system to compress 10 ps pulse down to 580 fs

Improved design of dispersion decreasing fiber for similariton pulse compression

Summary form only given. The rapid development in optical fiber amplifiers continues to have major impact on telecommunications and ultrafast optics, and opens up new possibilities for fundamental studies of nonlinear and dispersive pulse propagation in the presence of gain.

http://ieeexplore.ieee.org/iel5/7267/19606/00910275.pdf

Self-similar propagation of parabolic pulses in high gain optical amplifiers

The generation of self-similar parabolic pulses (similaritons) has so far only been obtained in single-pass Raman amplifier configurations [1–3] or in rare-earth doped fiber lasers [4–6]. We report here the first demonstration of a mode-locked parabolic pulse fiber laser, which can potentially be run at any wavelength using Raman gain. This new all-fiber ring similariton laser scheme [Fig.1] has been designed with the aid of a full theoretical model of its operation. The output similariton pulses of the laser have a true parabolic shape and a linear chirp.

Mode-locked parabolic Raman fiber oscillator

We present an analytical solution for parabolic similaritons with saturation effects and new self-similar linearly chirped pulses generated in normal dispersion fibers with fast decaying gain, the Hyper-Gaussian pulse, suitable for low energy systems.

Parabolic and Hyper-Gaussian similaritons propagating in fiber amplifier and lasers with saturation effect

We report on a new similariton fibre laser system based on a nonlinear amplifying loop mirror The laser is robust and produces linearly chirped pulses that can be recompressed to 350fs

Vladimir Kruglov

Papers

Improved design of dispersion decreasing fiber for similariton pulse compression

Self-similar propagation of parabolic pulses in high gain optical amplifiers

Mode-locked parabolic Raman fiber oscillator

Parabolic and Hyper-Gaussian similaritons propagating in fiber amplifier and lasers with saturation effect

Environmentally stable, passively modelocked, all-normal dispersion fibre similariton laser