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The Maxwell-Bloch equations (MBE) describe the interaction between a two-level quantum mechanical system and an electromagnetic wave. They are widely used in nonlinear optics in general and to model quantum cascade lasers (QCLs) in particular [1]. Due to their nonlinearity, numerical methods are usually required to solve the equations. In order to cope with the computational complexity that arises,...
Shock waves have been thoroughly investigated during the last century in many different branches of physics. In conservative (Hamiltonian) systems the shock singularity is regularized by weak wave dispersion, thus leading to the formation of a rapidly and regular oscillating structure, usually termed in the literature dispersive shock wave (DSW), see e.g. [1]. Here, we show that this fundamental singular...
Multimode fibers (MMF) recently received considerable attention to realize space-division multiplexed (SDM) transmission systems, in order to increase the capacity of optical transmission systems. The nonlinear signal propagation in MMFs systems can be described by the nonlinear Schrödinger or the Manakov equation [1]. These are commonly solved numerically by applying split-step Fourier methods [2],...
Kerr micro-resonator frequency combs exhibit a variety of nonlinear phenomena, most prominently the formation of dissipative Kerr solitons (DKSs). These solitons are critical for applications in frequency metrology, precision time-keeping and ultrashort pulse generation. Thus far all studies of DKSs have been limited to single cavities [1, 2] or two uncoupled cavities [3-5], though coupled dual microring...
Squeezed states of light are referred to as non-classical field states and are known to be characterized by strong correlations between photons both in the spectral and spatial domain. For these reasons they are very perspective for many important and interesting practical applications in modern quantum optics including storage and transfer of quantum information. From this point of view multiphoton...
Realistically, any discussion of fiber-optic solitons must consider the impact of gain and loss. Even when both are balanced on average, pulse reshaping does occur, and radiation is generated (which drains energy from the soliton). Mathematically speaking, the Nonlinear Schrodinger Equation (NLSE) is integrable, and solitons are its solutions: but in the presence of only infinitesimal loss or gain,...
π-shifted distributed feedback (DFB) fiber Bragg grating (FBG) Raman lasers have been demonstrated in the last few years [1, 2] and many attempts at optimisation have been made using theoretical calculations [3]. However, due to the limitations of resolution of the coupled-mode equations, theoretical optimisation has been limited to a few case studies. By using a simple approximation, we demonstrate...
The recent findings of line narrowing in Raman-active continuous-wave-pumped gas [1] showed that the Stokes scattering occurs in a Lamb-Dicke regime and is associated to formation of array of deep subwavelength nanotraps, which resulted in a sub-recoil linewidth Stokes radiation [1]. The results also showed that this nanotrap lattice exhibits a macroscopic motion. Here we present theoretical and numerical...
The emergence of long range phase coherence among random nonlinear waves is a fascinating effect that characterizes many fundamental phenomena. For instance, the condensation of classical waves [1,2] is an important example of self-organization process that generates lot of interest as a classical analogue of quantum Bose-Einstein condensation. Wave condensation is known to be characterized by the...
Fully-structured light — light with non-uniform intensity, phase and polarisation — lies at the heart of an emerging and extremely promising field of research, with applications in high-resolution imaging, optical trapping and manipulation of nanoparticles, plasmonic lithography, and optical communication. We show that the interplay of polarisation structure and nonlinearity can be used as a means...
Recently, various research groups have studied spontaneous symmetry breaking and bistable behaviour in both active and passively driven coupled photonic nanocavities[1]. This work is of interest both in itself and because it naturally extends to coupled nonlinear quantum systems described by the Bose-Hubbard model [2]. Here we present a theoretical study of the dynamics in such a system by considering...
Pulsed Laser Ablation in Liquid (PLAL) is a flexible technique for synthesis of nanoparticles of various materials, in particular of noble metals [1]. Despite of the widespread use of this method, processes involved in PLAL are still poorly understood. The presence of the liquid makes the PLAL process much more complicated as compared to conventional ablation in vacuum or in an ambient gas. The poor...
Just five years after invention of the laser, laser induced periodic structures (LIPSS) had been reported [1]. However, the structure period is not very uniform in LIPSS. Recently, with nonlinear laser lithography (NLL), long range ordered periodic surface structures had been maintained by exploiting various feedback mechanisms and nonlinearities [2]. Albeit, fine tuning of structure period remains...
Mechanisms of spatiotemporal localization of femtosecond powerful pulses, the problems and conditions of light bullets (LB) stability, being key issues for many applications, nowadays remain challenging and largely unresolved tasks. Therefore these questions attract much attention of scientists. As is known, in Kerr media the filamentation makes possible the generation of spatially and temporally...
X-ray Free Electron Lasers (XFELs) are a new generation of x-ray sources, offering highly coherent, intense x-ray pulses with pulse lengths down to a few femtoseconds. Applications for intense X-ray pulses from XFELS span a broad spectrum from atomic and molecular physics to chemical, materials and biological sciences [1]. Recently, XFELs proved the ability to produce two intense femtosecond x-ray...
Over the past decade, the increasing potential of terahertz (THz) radiation has stimulated intensive efforts to develop efficient emitters based on the ionization of gases by ultrashort laser pulses [1]. In order to properly calibrate dedicated experiments, nonlinear propagation codes have to be particularly accurate to describe the low-frequency part of the pulse spectrum. Usually, solving full Maxwell...
In the traditional rate equation-approach to nanolasers, the active material is modelled as a collection of independent emitters [1], but in recent years it has become increasingly clear that radiative coupling of the emitters in the cavity can significantly change the characteristics of a (nano)laser under certain conditions [2-5]. The collective effects arising as an emitter-emitter coupling are...
Solid-state materials have recently emerged as a new stage for strong-field physics. Since the first observation of high-harmonic generation (HHG) from solids by Ghimire et al. [1], its mechanism is under intensive discussion.
Recent advance in generation of strong electric fields in the mid-infrared to terahertz regions triggers research on extremely fast electron transportation in crystalline solids with terahertz to petahertz frequencies and associated high harmonic generation (HHG) in the spectral regions from visible to vacuum ultraviolet beyond typical bandgaps of solids [1, 2]. So far, most of the experiments choose...
Recently some of us have shown that the use of a correct ab initio approach to nonlinear pulse propagation simulations during nonlinear optical device designing can result in threefold efficiency increase with respect to the efficiency of existing solutions [1]. In that work we have focused on small beam size, and thus, high divergence regime where the effects of diffraction, spatial and temporal...
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