Soliton fibre lasers mode-locked at a high harmonic of their round-trip frequency have many potential applications, from telecommunications to data storage(1). Control of multiple pulses in passively mode-locked fibre lasers has, however, proved very difficult to achieve. This has recently changed with the advent of fibre lasers mode-locked by intense optomechanical interactions in a short length of photonic crystal fibre(2,3). Optomechanical coupling between cavity modes gives rise to highly stable, optomechanically bound, laser soliton states. The repetition rate of these states corresponds to the mechanical resonant frequency in the photonic crystal fibre core(4), which can be a few gigahertz. Here we show that this system can be successfully used for programmable generation and storage of gigahertz-rate soliton sequences over many hours

Self-assembly of fundamental elements through weak, long-range interactions plays a central role in both supramolecular DNA assembly and bottom-up synthesis of nanostructures. Optical solitons, analogous in many ways to particles, arise from the balance between nonlinearity and dispersion and have been studied in numerous optical systems. Although both short- and long-range interactions between optical solitons have attracted extensive interest for decades, stable soliton supramolecules, with multiple aspects of complexity and flexibility, have thus far escaped experimental observation due to the absence of techniques for enhancing and controlling the long-range inter-soliton forces. Here we report that long-range soliton interactions originating from optoacoustic effects and dispersive-wave radiations can be precisely tailored in a fibre laser cavity, enabling self-assembly of large numbers of optical solitons into highly-ordered supramolecular structures. We demonstrate several features of such optical structures, highlighting their potential applications in optical information storage and ultrafast laser-field manipulation.

Ultrafast lasers with high repetition rates are of considerable interest in applications such as optical fiber telecommunications, frequency metrology, high-speed optical sampling, and arbitrary waveform generation. For fiber lasers mode-locked at the cavity round-trip frequency, the pulse repetition rate is limited to tens or hundreds of megahertz by the meter-order cavity lengths. Here we report a soliton fiber laser passively mode-locked at a high harmonic (similar to 2 GHz) of its fundamental frequency by means of optoacoustic interactions in the small solid glass core of a short length ( 60 cm) of photonic crystal fiber. Due to tight confinement of both light and vibrations, the optomechanical interaction is strongly enhanced. The long-lived acoustic vibration provides strong modulation of the refractive index in the photonic crystal fiber core, fixing the soliton spacing in the laser cavity and allowing stable mode-locking, with low pulse timing jitter, at gigahertz repetition rates. (C) 2015 Optical Society of Americ

Gasification of comingled biomass and coal feedstock is an effective means of reducing the net life cycle greenhouse gas emissions in the coal gasification process while maintaining its inherent benefits of abundance and high-energy density. However, feeding a comingled biomass and coal feedstock into a pressurized gasification reactor poses a technical problem. Conventional dry feeding systems, such as lock hoppers and pressurized pneumatic transport, are complex and operationally expensive. A slurry formation of comingled biomass and coal feedstock can be easily fed into the gasification reactor but, in normal conditions, only allows for a small portion of biomass in the mixture. This is a consequence of the hydroscopic and hydrophilic nature of the biomass. The College of Engineering Center for Environmental Research and Technology (CE-CERT) at the University of California, Riverside, has developed a process producing high solid content biomass-water slurry using a hydrothermal pretreatment process. In this paper, the systematic investigation of the rheological properties (e.g., shear rate, shear stress, and viscosity) of coal-water slurries, biomass-water slurries, and comingled biomass and coal-water slurries is reported. The solid particle size distribution in the slurry and the initial solid/water ratio were investigated to determine the impact on shear rate and viscosity. This was determined using a rotational rheometer. The experimental results show that larger particle size offers better pumpability. The presence of a high percentage of biomass in solid form significantly decreases slurry pumpability. It is also shown that the solid loading of the biomass-water slurry can be increased to approximately 35 wt % with viscosity of less than 0.7 Pa 3 s after the pretreatment process. The solid loading increased to approximately 45 wt % when the biomass is comingled with coal.

Compact and powerful ultrafast light sources at high pulse repetition rates, based on mode-locked near infrared fiber lasers, are now widely available and are being used in applications such as frequency metrology, molecular spectroscopy, and laser micro-machining. The realization of such lasers in the mid-infrared has, however, remained a challenge for many years. Here we report a record-breaking three-stage fiber laser system that uses an Er-doped fluoride fiber as gain medium, delivering W-level few-cycle pulses at 2.8 µm at a repetition rate of 42.1 MHz. A fiber-based seed oscillator, cavity dispersion-managed by a pulse-stretcher, generates near-100-fs mid-infrared pulses with > 110 n m spectral bandwidth. These pulses are amplified to an average power of ∼ 1 W in a chirp-engineered fiber amplifier, and then compressed to ∼ 16 f s in a short length of highly nonlinear ZBLAN fiber, resulting in a more-than-octave-wide spectrum reaching from 1.8 µm to 3.8 µm with a total power of 430 mW.

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Mode-locked lasers have been widely used to explore interactions between optical solitons, including bound-soliton states that may be regarded as “photonic molecules”. Conventional mode-locked lasers normally, however, host at most only a few solitons, which means that stochastic behaviours involving large numbers of solitons cannot easily be studied under controlled experimental conditions. Here we report the use of an optoacoustically mode-locked fibre laser to create hundreds of temporal traps or “reactors” in parallel, within each of which multiple solitons can be isolated and controlled both globally and individually using all-optical methods. We achieve on-demand synthesis and dissociation of soliton molecules within these reactors, in this way unfolding a novel panorama of diverse dynamics in which the statistics of multi-soliton interactions can be studied. The results are of crucial importance in understanding dynamical soliton interactions and may motivate potential applications for all-optical control of ultrafast light fields in optical resonators.

Current pulsed fiber lasers that are capable of delivering stable sub-100-fs pulses at megahertz repetition rates require intracavity pulse energies in the nanojoule range. Scaling these lasers to gigahertz repetition rates necessitates, therefore, very high average power levels and complex cladding-pumped configurations. Here we report a type of stretchedsoliton all-fiber laser that generates broadband, soliton-like pulses at 1.55 μm with intracavity pulse energies of only tens of picojoules. In the laser cavity, strong dispersion management leads to a temporal breathing ratio of ∼70, while the weak residual anomalous dispersion is perfectly balanced by the low Kerr nonlinearity, resulting in the formation of temporally stretched, hyperbolic-secant pulses. A lumped wavelength-dependent attenuator compensates for the effects of the gain filtering on the pulse spectrum, ensuring intracavity pulse self-consistency. This unique stretchedsoliton mechanism, combined with a harmonic mode-locking technique based on intense optoacoustic interactions in solid-core photonic crystal fiber, yields for the first time stable gigahertz-rate, sub-100-fs, dispersive-wave-free pulse trains at moderate pump powers.