Soliton dynamics in the multiphoton plasma regime

Solitary waves have consistently captured the imagination of scientists, ranging from fundamental breakthroughs in spectroscopy and metrology enabled by supercontinuum light, to gap solitons for dispersionless slow-light, and discrete spatial solitons in lattices, amongst others. Recent progress in strong-field atomic physics include impressive demonstrations of attosecond pulses and high-harmonic generation via photoionization of free-electrons in gases at extreme intensities of 1014 Wcm2. Here we report the first phase-resolved observations of femtosecond optical solitons in a semiconductor microchip, with multiphoton ionization at picojoule energies and 1010 Wcm2 intensities. The dramatic nonlinearity leads to picojoule observations of free-electron-induced blue-shift at 1016 cm3 carrier densities and self-chirped femtosecond soliton acceleration. Furthermore, we evidence the time-gated dynamics of soliton splitting on-chip, and the suppression of soliton recurrence due to fast free-electron dynamics. These observations in the highly dispersive slow-light media reveal a rich set of physics governing ultralow-power nonlinear photon-plasma dynamics.Comment: 14 pages (main body and supplement), 11 figures - earlier draft; http://www.nature.com/srep/2013/130122/srep01100/full/srep01100.htm

Carbon chloride-core fibers for soliton mediated supercontinuum generation

We report on soliton-fission mediated infrared supercontinuum generation in liquid-core step-index fibers using highly transparent carbon chlorides (CCl4, C2Cl4). By developing models for the refractive index dispersions and nonlinear response functions, dispersion engineering and pumping with an ultrafast thulium fiber laser (300 fs) at 1.92 μm, distinct soliton fission and dispersive wave generation was observed, particularly in the case of tetrachloroethylene (C2Cl4). The measured results match simulations of both the generalized and a hybrid nonlinear Schrödinger equation, with the latter resembling the characteristics of non-instantaneous medium via a static potential term and representing a simulation tool with substantially reduced complexity. We show that C2Cl4 has the potential for observing non-instantaneous soliton dynamics along meters of liquid-core fiber opening a feasible route for directly observing hybrid soliton dynamics

Third harmonic generation in liquid core optical fibres

The objective of this thesis is to investigate third harmonic generation in liquid core fibres. Such fibres are formed by injection of liquid into a hollow, solid cladding by capillary forces. Carbon disulphide and tetrachloroethylene are identified as most promising liquid candidates. Such liquids offer a strong nonlinearity whose major contribution is non-instantaneous arising from the molecular structure. The effect of this material response during harmonic generation is investigated numerically by solving coupled evolution equations and causes distinct spectral shifts and broadening of both harmonic and fundamental wave. Both liquids offer excellent transparency and a high index of refraction enabling intermodal phase matching in a step-index geometry without requiring a complex microstructure. Aspects of fibre design and experimental realisation are presented in detail. Using sub-picosecond pump pulses of different duration the harmonic is generated in a higher order fibre mode and resulting signals are analysed in the spectral domain. Modification of the fibre cross-section towards an elliptical core is investigated. Besides the induced birefringence, harmonic generation in further sets of higher order modes is possible due to their transformation of electric fields. Design considerations of spatially modified fibres were confirmed experimentally and adaptive phase matching by controlling fibre temperature could be realised. Feasibility of long term exposure of liquid filled fibres to high average powers of femtosecond pulses is demonstrated underpinning that liquid core fibres withstand practical applications beyond laboratory use. Finally, possible routes to enhance the currently achieved conversion efficiencies for tetrachloroethylen of 2 ∙ 10^-5, and carbon disulphide of 10^-7, are identified and future prospects of this fibre platform are discussed