Propagation Of Light Pulses Research Articles

Transversally travelling ultrasound for light guiding deep into scattering media

The application of optical methods for tissue diagnosis, activation, and treatment suffers dramatically from the low accessible depths due to strong light scattering in tissues. Here we demonstrate a method to address this issue by utilizing transient ultrasound waves, travelling transversally to the light propagation direction, to guide light into deeper tissue regions. We study the formation of the ultrasound-induced refractive index structures and waveguides using simple ultrasound field configurations and analyze their effects on the propagation of short light pulses. As a proof of concept, we demonstrate using 5 ns pulses of 532 nm light and Intralipid-20%-based phantoms with mu _{mathrm{s}}^prime up to 4.5 cm−1 a waveguide supported light intensity increase up to the depths of at least 90 mean free paths.

Diffraction Limit in Theory of Light Bullets

An averaged variational procedure has been developed to study the propagation of light bullets in optical fibers using the propagation of light pulses in media with Kerr and quadratic nonlinearities as examples. Criteria for the correct choice of trial solutions are discussed. The condition under which the dispersion length is much greater than the length of diffraction spreading is called the diffraction limit. It is shown that, in this limit, the temporal and spatial dynamics of a bullet are independent of each other, while finding the dynamic parameters of a soliton is reduced to finding various solutions of the nonstationary linear Schrodinger equation for an imaginary quantum particle. The efficiency of the proposed approach is demonstrated by the example of finding solutions in the form of optical vortices in a waveguide for nonlinearities of both types.

Soliton solutions of the Sasa–Satsuma equation in the monomode optical fibers including the beta-derivatives

The main goal of the present paper is to steer an investigation on the dynamics of soliton solutions of a nonlinear model in the monomode optical fibers. In this respect, first, soliton solutions of the model termed as the Sasa–Satsuma (SS) equation describing the propagation of short light pulses are derived in the presence of the beta-derivatives; then, the dynamics of soliton solutions in the monomode optical fibers is analyzed for different values of the parameter β. The soliton solutions presented in this study are categorized in the most common classes of solitons namely bright and dark soliton solutions.

Random walks of trains of dissipative solitons

The propagation of light pulses in dual-core nonlinear optical fibers is studied using a model proposed by Sakaguchi and Malomed. The system consists of a supercritical complex Ginzburg-Landau equation coupled to a linear equation. Our analysis includes single standing and walking solitons as well as walking trains of 3, 5, 6, and 12 solitons. For the characterization of the different scenarios, we used ensemble-averaged square displacement of the soliton trajectories and time-averaged power spectrum of the background waves. Power law spectra, indicative of turbulence, were found to be associated with random walks. The number of solitons (or their separations) can trigger anomalous random walks or totally suppress the background waves.

On the Propagation of Short Electromagnetic Pulses through Quantum Metamaterials

In this paper, we analyse the propagation of a short light pulse through a 1D quantum metamaterial structure, composed of arranged artificial two-level quantum systems. We set up the model which material substance is treated quantum mechanically, while the electromagnetic pulse is classical. On the basis of the adopted model, we investigate the short light pulse propagation through the structure in dependence on the initial state of irradiated two-level systems, the amplitude of the incident light pulse, and the frequency of the pulse carrier wave. Finally, we determine the regimes when the incident pulse can propagate in undistorted soliton form.

Material slow and fast light in a zero-dispersion configuration

We study the propagation of light pulses in an absorbing medium when the frequency of their carrier coincides with a zero of the refractive index dispersion. Although slow light and, a fortiori, fast light are not expected in such conditions, we show that both can be obtained by selecting particular phase components of the transmitted field. Analytical expressions of the resulting signals are obtained by a procedure of periodic continuation of the incident pulse, and a proof of principle of the predicted phenomena is performed by means of a very simple electrical network; the transfer function of which mimics that of the medium.

Light pulse propagation in a double prism layout close to the angle of total internal reflection

Both transmission and reflection of a short light pulse are considered for a double prism system in the geometry of in-gap refraction with an account of material dispersion. Within a frame of linear optics and Snell refraction law, we revealed the effect of a ‘negative dispersion’ regime close to the total internal reflection. A narrow area of parameters (wave number and angle of incidence) in the close vicinity of the total internal reflection is found to possess specific properties for the refracted field. A resonance excitation of leaky waveguide modes enables to extract the refracted field from the gap efficiently and inspect various transmission regimes. Analytical consideration and simulations demonstrate an appearance of advanced pulse in the transmitted and reflected waveforms, with the temporal shape depending on a number of modes enclosed in a spectral width of an incident pulse as well as the existence of elongated precursor within a gap.

Propagation of dipole solitons in inhomogeneous highly dispersive optical-fiber media.

We consider ultrashort light pulse propagation through an inhomogeneous monomodal optical fiber exhibiting higher-order dispersive effects. Wave propagation is governed by a generalized nonlinear Schrödinger equation with varying second-, third-, and fourth-order dispersions, cubic nonlinearity, and linear gain or loss. We construct a type of exact self-similar soliton solution that takes the structure of a dipole via a similarity transformation connected to the related constant-coefficients one. The conditions on the optical-fiber parameters for the existence of these self-similar structures are also given. The results show that the contribution of all orders of dispersion is an important feature to form this kind of self-similar dipole pulse shape. The dynamic behaviors of the self-similar dipole solitons in a periodic distributed amplification system are analyzed. The significance of the obtained self-similar pulses is also discussed. By performing numerical simulations, the self-similar soliton solutions are found to be stable under slight disturbance of the constraint conditions and the initial perturbation of white noise.

On the Propagation of a Short Light Pulse in a Medium With a Lorentz Contour of the Spectral Gain Line

On the Propagation of a Short Light Pulse in a Medium With a Lorentz Contour of the Spectral Gain Line

Triangular Rogue Waves and Multi- Wave Trains Generation in a Chameleon Electrical Transmission Line

In this work, we present a particular nonlinear transmission line called chameleon nonlinear transmission line. In fact, the chameleon’s behavior is related to the fact that without changing its appearance, the line can exhibit alternatively purely right - or left - handed behavior. This transmission line is different to the composite one. So, the goal of this work is to demonstrate that this special line can support the propagation of soliton light pulse subjected to quintic – phase modulation, improve the freak wave’s mechanism of generation and verify the chameleon’s behavior of the line. Consequently, we employ collective coordinate’s theory in order to give a great characterization of the light pulse. Then, we introduce an upgraded function called “type II Ansatz function” with eight collective coordinates compared to the conventional Gaussian Ansatz with six collective coordinates. We show that the two additional coordinates will allow us to improve the technique of measurement of internal excitation leading to the generation of rogue events. Moreover, these coordinates will give supplemental details on frequency shift and chirp distortions during the generation of specific rogue events such as “wall of waves”, tree structures, multi - wave trains, Kuznetsov - Ma breathers, Akhmediev breathers, Peregrine solitons and triangular rogue waves. The stability of the soliton light pulse will be also investigated at specific frequency ranges.

Numerical analysis of the Hirota equation: Modulational instability, breathers, rogue waves, and interactions.

In this paper, we focus on the integrable Hirota equation, which describes the propagation of ultrashort light pulses in optical fibers. First, we numerically study spectral signatures of the spatial Lax pair with distinct potentials [e.g., solitons, Akhmediev-Kuznetsov-Ma (AKM) and Kuznetsov-Ma (KM) breathers, and rogue waves (RWs)] of the Hirota equation. Second, we discuss the RW generation by using the dam-break problem with a decaying initial condition and further analyze spectral signatures of periodized wavetrains. Third, we explore two kinds of noise-derived modulational instabilities: (i) the one case is based on the initial condition (one plus a random noise) such that the KM and AKM breathers, and RWs can be generated, and they agree well with analytical solutions; (ii) another case is to consider another initial condition (one plus a Gaussian wave with a random noise phase) such that some RWs with higher amplitudes can be found. Moreover, we also investigate the spectral signatures of corresponding periodic wavetrains. Finally, we find that the interactions of two waves can also generate the RW phenomena with higher amplitudes. These obtained results will be useful to understand the RW generation in the third-order nonlinear Schrödinger equation and other related models.

Slow light pulse propagation through spherical quantum dot with on-center hydrogen impurity in magnetic field

Abstract The probe pulse propagation through the spherical quantum dot with an on-center hydrogen impurity in an external magnetic field in the regime of the electromagnetically induced transparency is studied in detail. The interaction of this quantum system with the weak pulse probe and strong continuous wave control laser is described by the three-level ladder-type configuration. By solving Maxwell-Bloch equations with the help of the Fourier transform method, the approximate analytic expressions for the probe pulse envelope and probe pulse group velocity are obtained. We investigate the influence of the magnetic field strength and dephasing rates on slowing down the probe pulse and on its shape during the propagation. We found that the magnetic field can additionally reduce the group velocity of the probe pulse. It has also been found that reducing dephasing rates enables the weak probe pulse propagation with almost negligible losses. The obtained analytic expressions are in the good agreement with the numerical calculations.

Propagation of megawatt subpicosecond light pulses with the minimum possible shape and spectrum distortion in an air- or argon-filled hollow-core revolver fibre

We have examined the feasibility of undistorted subpicosecond pulse transmission at peak powers of up to 100 MW and a wavelength of 1030 nm in a hollow-core revolver fibre having a core filled with atmospheric air or argon. A hollow-core revolver fibre has been fabricated which has a low-dispersion (β2 ≈ – 0.25 ps2 km−1) transmission band in the spectral range of ytterbium and neodymium lasers. Conditions for the nonlinear (soliton) regime of megawatt picosecond pulse propagation over up to 1-km lengths of revolver fibre in atmospheric air and argon at pressures in the range 10−5 to 1 atm have been found theoretically. We have experimentally demonstrated transmission of pulses of 0.8-ps duration and up to ∼100-MW power over an ∼3-m length of revolver fibre with the minimum possible distortion of their shape and spectrum.

Bright and dark solitons in (n + 1)-dimensions with spatio-temporal dispersion

This work is devoted to scrutinize new optical soliton solutions to the spatially temporal (n + 1)-dimensional nonlinear Schrodinger’s equation. The initial ansatz supposed in the form of Jacobi elliptic functions to obtain dark and bright optical solitons in the presence of different non-Kerr media. Kerr law, power law, parabolic law and dual-power law have been utilized as nonlinear medium. The fetched results are new and useful for the propagation of light pulses in optical fibers. For the existence of these solitons constraint conditions are also listed.

Highly efficient deep UV generation by four-wave mixing in gas-filled hollow-core photonic crystal fiber.

We report on a highly efficient experimental scheme for the generation of deep-ultraviolet (UV) ultrashort light pulses using four-wave mixing in gas-filled kagomé-style photonic crystal fiber. By pumping with ultrashort, few microjoule pulses centered at 400nm, we generate an idler pulse at 266nm and amplify a seeded signal at 800nm. We achieve remarkably high pump-to-idler energy conversion efficiencies of up to 38%. Although the pump and seed pulse durations are ∼100 fs, the generated UV spectral bandwidths support sub-15fs pulses. These can be further extended to support few-cycle pulses. Four-wave mixing in gas-filled hollow-core fibers can be scaled to high average powers and different spectral regions such as the vacuum UV (100-200nm).

Dispersionless limit of the (1+1)-dimensional Fokas-Lenells equation

Nonlinear dispersionless equations can be obtained as dispersionless limits (quasiclassical limits) of integrable hierarchies of equations or by constructing a system of hydrodynamic type. In this paper, the dispersionless limit of the (1+1)-dimensional Fokas-Lenells equation is found. We present Lax pair for this dispersionless equation. As well known, the Fokas-Lenells equation characterizes the propagation of ultrashort nonlinear light pulses in optical fibers. Exact solutions of the dispersionless version of the Fokas-Lenells equation describe nonlinear shock waves in optical fiber systems. By using the obtained results, one can find shock wave solutions of the dispersionless equation, which have different physical applications.

Modified nonlinear Schrödinger equation for frequency-dependent nonlinear profiles of arbitrary sign

In recent times, materials exhibiting frequency-dependent optical nonlinearities, such as nanoparticle-doped glasses and other metamaterials, have gathered significant interest. The simulation of the propagation of intense light pulses in such media, by means of the nonlinear Schrodinger equation (NLSE), poses the problem in that straightforward inclusion of a frequency-dependent nonlinearity may lead to unphysical results, namely, neither the energy nor the photon number is conserved in general. Inspired by a simple quantum-mechanical argument, we derive an energy- and photon-conserving NLSE (pcNLSE). Unlike others, our approach relies only on the knowledge of the frequency-dependent nonlinearity profile and a generalization of Miller’s rule for nonlinear susceptibility, enabling the simulation of nonlinear profiles of arbitrary frequency dependence and sign. Moreover, the proposed pcNLSE can be efficiently solved by the same numerical techniques commonly used to deal with the NLSE. Relevant simulation results supporting our theoretical approach are presented.

Coherent generation and manipulation of stationary light pulses encoded in degrees of freedom of polarization and orbital angular momentum

We propose a double-$\mathsf{M}$ system of cold atoms for realizing the reversible storage and manipulation of signal fields encoded in degrees of freedom (DOFs) of polarization and orbital angular momentum (OAM). By employing two pairs of counterpropagating controlling fields, we show that the system exhibits dark state polaritons relating to the polarization and propagation direction of the light fields. Through the active operation of the controlling fields in time, stationary light pulses with polarizations and OAM information can be generated due to the tight coupling and balanced competition between the retrieved signal fields, and can be manipulated coherently and all-optically. Another advantage of our proposed scheme is that the two polarization components of the signal field can be decoupled and thus be independently retrieved from the atomic ensemble, and then the scheme can be employed to realize polarization-dependent beam splitting. Such a multiple DOF-dependent scheme could pave the way toward quantum nonlinear optics without a cavity, and could greatly enhance the tunability and capacity for both classical and quantum information processing.

Reconstruction of coherent anti‐Stokes Raman scattering signals generated by means of laser pulses with asymmetric amplitude and phase

AbstractTime and frequency asymmetries in ultrashort chirped laser fields might appear as a consequence of dispersive propagation, pulse shaping techniques, or generation of auxiliary light pulses needed in nonlinear optics. Here, we try to find an answer to the question of how to solve analytically coherent anti‐Stokes Raman scattering (CARS) under asymmetric conditions of chirped femtosecond laser pulses. The approach breaks in two parts. One for the field amplitudes and the other for the phases. The former revolves around Gaussian dependences that, besides being rather common in ultrashort laser physics, can be arranged and mixed to reproduce spectrally asymmetric laser amplitudes. The latter is limited to field phases with cubic frequency dependence (i.e., second‐order chirp) whose asymmetry is simulated by adding a linear term to the quadratic phase. Both approximations for amplitudes and phases of the three laser pulses are mandatory to guarantee the solution to the complexity posed by the CARS problem. Comparisons with known experimental and numerical results support the validity of the model.

Self-consistent quantum-kinetic theory for interplay between pulsed-laser excitation and nonlinear carrier transport in a quantum-wire array.

We propose a self-consistent many-body theory for coupling the ultrafast dipole-transition and carrier-plasma dynamics in a linear array of quantum wires with the scattering and absorption of ultrashort laser pulses. The quantum-wire non-thermal carrier occupations are further driven by an applied DC electric field along the wires in the presence of resistive forces from intrinsic phonon and Coulomb scattering of photo-excited carriers. The same strong DC field greatly modifies the non-equilibrium properties of the induced electron-hole plasma coupled to the propagating light pulse, while the induced longitudinal polarization fields of each wire significantly alters the nonlocal optical response from neighboring wires. Here, we clarify several fundamental physics issues in this laser-coupled quantum wire system, including laser pulse influence on local transient photo-currents, photoluminescence spectra, and the effect of nonlinear transport in a micro-scale system on laser pulse propagation. Meanwhile, we also anticipate some applications from this work, such as specifying the best combination of pulse sequence through a quantum-wire array to generate a desired THz spectrum and applying ultra-fast optical modulations to nonlinear carrier transport in nanowires.