Ultrashort Soliton Research Articles

Derivation of a generalized double-sine-Gordon equation describing ultrashort-soliton propagation in optical media composed of multilevel atoms

We consider the propagation of ultrashort optical solitons in media described by a general Hamiltonian of multilevel atoms. Assuming that all transition frequencies of the medium are well below the typical wave frequency, i.e., only the contribution of infrared transitions is taken into account, we use a short-wave approximation and a rigorous application of the reductive perturbation formalism to derive a cumbersome coupled system of nonlinear partial differential equations describing ultrashort soliton evolution in such systems. The rather complicated set of coupled equations can be simplified to a generic double-sine-Gordon equation for a special case of identical three-level atoms, whereas for a special case of identical four-level atoms the system of coupled equations can be reduced to a generalized double-sine-Gordon equation. Numerical simulations showing the formation of robust breather-type solutions of both the standard double-sine-Gordon and of the generalized double-sine-Gordon equations from sinusoidal inputs with Gaussian envelopes are also presented.

Ultra-Short of Pico and Femtosecond Soliton Laser Pulse Using Microring Resonator for Cancer Cells Treatment

A system of microring resonators (MRRs) incorporating with an add/drop filter system is presented in which ultra-short single and multi temporal and spatial optical soliton pulses can be simulated and used to thermalbased killing of abnormal cells, tumor and cancer, applicable in nanomedical treatments. This proposed system uses chaotic signals generated by a bright soliton pulse within a nonlinear MRRs system. Interaction between gold nanoparticles and ultra-short femtosecond and picosecond laser pulses holds great interest in laser nanomedicine. By using the appropriate soliton input power and MRRs parameters, required spatial and temporal signals are generated spreading over the spectrum. Results obtained show that smallest single temporal and spatial soliton pulse with FWHM = 712 fs and FWHM = 17.5 pm could be generated respectively. The add/drop filter system is used to generate high capacity ultra-short soliton pulses in the range of nanometer/second and picometer/second.

Symbolic computation on soliton dynamics and Bäcklund transformation for the generalized coupled nonlinear Schrödinger equations with cubic-quintic nonlinearity

In this paper, we study the generalized coupled nonlinear Schrödinger equations with the cubic-quintic nonlinearity and arbitrary coupling parameters which describe the effects of the quintic nonlinearity on the ultrashort optical soliton pulse propagation in the non-Kerr media. Dark–dark N- and bright–dark two-soliton solutions are derived with symbolic computation. The bilinear Bäcklund transformation and the corresponding one-soliton solution are also given. Interactions of the dark–dark solitons including the repulsive and coherent interactions are investigated analytically and graphically, which are different from those in previous studies. The relationship between the amplitude and the velocity of the dark soliton is studied, especially the soliton with the small amplitude catches up with the one with the large amplitude. Head-on and overtaking interactions of dark–dark solitons are presented. Interactions between a stationary dark soliton and another dark one are shown. The asymptotic analysis shows that the interaction of dark–dark two solitons is elastic. The periodic attraction and repulsion of the bright–dark two solitons in the bound state are also analyzed, which are in accordance with those in the bright–dark vector soliton studies but different from the asymmetric and symmetric stationary bound states of Manakov bright–dark solitons.

Spatiotemporal optical solitons in carbon nanotube arrays

We consider the formation of ultrashort spatiotemporal optical waveforms in arrays of carbon nanotubes. We use a short-wave approximation to derive a generic two-dimensional sine-Gordon equation, describing ultrashort soliton evolution in such nanomaterials. This model was derived by using a rigorous application of the reductive perturbation formalism (multiscale analysis) for the Maxwell equations and for the corresponding Boltzmann kinetic equation for the distribution function of electrons in carbon nanotubes. We show numerically diffractionless and dispersionless robust propagation over large distances (with respect to the wavelength) of few-cycle (2+1)-dimensional spatiotemporal solitons in the form of optical breathers.

Ultra-short Laser Pulse Generated by a Microring Resonator System for Cancer Cell Treatment

A microring resonator (MRRs) system incorporated with a add/drop filter is proposed in which ultra-short single, multi-temporal, and spatial optical soliton pulses are simulated and used to kill abnormal cells, tumors, and cancer. Chaotic signals are generated by a bright soliton pulse within a nonlinear MRRs system. Gold nanoparticles and ultra-short femtosecond/picosecond laser pulses’ interaction holds great interest in laser nanomedicine. By using appropriate soliton input power and MRRs parameters, desired spatial and temporal signals can be generated over the spectrum. Results show that short temporal and spatial solitons pulse with FWHM = 712 fs and FWHM = 17.5 pm could be generated. The add/drop filter system is used to generate the high-capacity, ultra-short soliton pulses in the range of nanometer/second and picometer/second.

Derivation of a coupled system of Korteweg–de Vries equations describing ultrashort soliton propagation in quadratic media by using a general Hamiltonian for multilevel atoms

We consider the propagation of ultrashort solitons in noncentrosymmetric quadratically nonlinear optical media described by a general Hamiltonian of multilevel atoms. We use a long-wave approximation to derive a coupled system of Korteweg--de Vries equations describing ultrashort soliton evolution in such materials. This model was derived by using a rigorous application of the reductive perturbation formalism (multiscale analysis). The study of linear eigenpolarizations in the degenerate case and the corresponding formation of half-cycle solitons from few-cycle-pulse inputs are also presented.

Symbolic computation on the bright soliton solutions for the generalized coupled nonlinear Schrödinger equations with cubic–quintic nonlinearity

Under investigation in this paper are the generalized coupled nonlinear Schrödinger equations with cubic–quintic nonlinearity which describe the effects of the quintic nonlinearity on the ultrashort optical soliton pulse propagation in the non-Kerr media. Via the dependent variable transformation and Hirota method, the bilinear form is derived. Based on the bilinear form obtained, the one-, two- and three-soliton solutions are presented in the form of exponential polynomials with the help of symbolic computation. Propagation and interactions of solitons are investigated analytically and graphically. Evolution of one soliton is discussed with the analysis of such physical quantities as the soliton amplitude, width, velocity, initial phase and energy. Interactions of the solitons appear in the forms of the repulsion or attraction alternately and propagation in parallel. Inelastic and head-on interactions of the solitons are also showed. Finally, via the asymptotic analysis, conditions of the elastic and inelastic interactions are obtained.

Coherent ultrashort pulse generation from incoherent light by pulse trapping in birefringent fibers

We investigated the nonlinear fiber phenomena of pulse trapping and amplification between incoherent light and an ultrashort soliton pulse in birefringent fibers both experimentally and numerically. Using the phenomena in a 1.4 km-long low-birefringence fiber, a coherent, nearly transform-limited, sech2-shaped, ultrashort pulse was generated from incoherent light from a super-luminescent diode. The average pulse energy and pulse width were 121 pJ and 640 fs, respectively. The estimated gain of this system was as large as 62 dB.

Partition of the instantaneous and delayed nonlinear responses for the propagation of ultrashort solitons in optical fibers

We address the long-standing issue of accurately partitioning the nonlinear response of silica glass into electronic (Kerr) and nuclear (Raman) contributions to correctly describe the propagation of ultrashort solitons in a unified way independently of their duration. This is done with a semianalytical approach leading to a modified nonlinear coefficient and thus to a modified condition for fundamental soliton propagation valid for durations much less, in the same order, or much greater than the characteristic time scale of the Raman response function. The results provided by this model are in good agreement with numerical integration of the nonlinear Schr\"odinger equation taking the Raman response into account.

Derivation of a modified Korteweg–de Vries model for few-optical-cycles soliton propagation from a general Hamiltonian

Propagation of few-cycles optical pulses in a centrosymmetric nonlinear optical Kerr (cubic) type material described by a general Hamiltonian of multilevel atoms is considered. Assuming that all transition frequencies of the nonlinear medium are well above the typical wave frequency, we use a long-wave approximation to derive an approximate evolution model of modified Korteweg–de Vries type. The model derived by rigorous application of the reductive perturbation formalism allows one the adequate description of propagation of ultrashort (few-cycles long) solitons.

Theory of Photoionization-Induced Blueshift of Ultrashort Solitons in Gas-Filled Hollow-Core Photonic Crystal Fibers

We show theoretically that the photoionization process in a hollow-core photonic crystal fiber filled with a Raman-inactive noble gas leads to a constant acceleration of solitons in the time domain with a continuous shift to higher frequencies, limited only by ionization loss. This phenomenon is opposite to the well-known Raman self-frequency redshift of solitons in solid-core glass fibers. We also predict the existence of unconventional long-range nonlocal soliton interactions leading to spectral and temporal soliton clustering. Furthermore, if the core is filled with a Raman-active molecular gas, spectral transformations between redshifted, blueshifted, and stabilized solitons can take place in the same fiber.

Ultrafast all-optical signal regenerator using pulse trapping in birefringent fibers

We demonstrated an all-optical signal control technique, novel to our knowledge, based on pulse trapping and amplification by ultrashort soliton pulse in a birefringent fiber to implement three functions: amplification, reshaping, and retiming. The signal and control pulses trap each other and copropagate in the fiber. The signal pulse experiences Raman gain and soliton effect by an ultrashort control pulse. The characteristics were investigated both experimentally and numerically. The maximum gain obtained was 28 dB in a 140 m long fiber. The output waveforms were ∼300 fs, chirp-free, sech2-shaped, ultrashort pulses. Delays and advances within ±0.4 ps in the initial signal were compensated for.

Time-domain near-infrared spectroscopy using a wavelength-tunable narrow-linewidth source by spectral compression of ultrashort soliton pulses

Time-domain absorption spectroscopy was demonstrated using a wideband, rapid wavelength-tunable, narrow-linewidth source based on an Er-doped ultrashort pulse fiber laser system. The spectrum of the Raman-shifted ultrashort soliton pulse was compressed using a comb-profile dispersion increasing fiber. Rapid wavelength sweeping was demonstrated using an electro-optical intensity modulator. The absorption spectrum of CH(2)Cl(2) liquid at 1625-1780 nm was observed in a 10 μs time-domain measurement.

超短光脉冲在双芯光子晶体光纤中的非线性传输和孤子开关现象的产生

超短光脉冲在双芯光子晶体光纤中的非线性传输和孤子开关现象的产生

パルス捕捉現象を用いた超短ソリトンパルスによるcw光からの超短パルス光生成

パルス捕捉現象を用いた超短ソリトンパルスによるcw光からの超短パルス光生成

Ultrashort pulse generation from continuous wave by pulse trapping in birefringent fibers

We investigated the phenomenon of orthogonally polarized pulse trapping between a continuous-wave beam and an ultrashort soliton pulse in birefringent fibers both experimentally and numerically. Using pulse trapping and amplification, we demonstrated ultrashort pulse generation from a continuous-wave beam. The generated pulse had a nearly transform-limited sech(2)-shape and a temporal width of 350 fs. The obtained maximum pulse energy was 300 pJ using a 400 m-long low-birefringence fiber, and the corresponding gain was as large as 41 dB.

Ultrashort soliton pulses in the modified nonlinear Schrödinger equation with distributed coefficients in inhomogeneous fibers

This paper investigates a variable-coefficient modified nonlinear Schrodinger model for describing the ultrashort pulse dynamics with the distributed dispersion, self-phase modulation, self-steepening and linear gain/loss. Under specified soliton management conditions, the bright one- and two-soliton solutions are analytically derived by the Hiroa bilinear method. Dynamical behaviors and main features of the ultrashort pulse propagation in inhomogeneous fibers are discussed by analyzing some important physical quantities. Additionally, interactions of two neighboring ultrashort pulses with varying management parameters are investigated in detail. Results obtained in this paper will be of certain value to the studies on the propagation and application of the ultrashort pulse in the dispersion-managed fiber system.

Wideband spectral compression of wavelength-tunable ultrashort soliton pulse using comb-profile fiber

We demonstrated spectral compression of ultrashort soliton pulses in a wide wavelength region based on an adiabatic soliton spectral compression technique using a comb-profile fiber. The comb-profile fiber was carefully designed using numerical analysis and fabricated using a conventional single-mode fiber and a dispersion-shifted fiber. The spectral width of a 200 fs soliton pulse was compressed from 12 to 15 nm to 0.54-0.71 nm in the wavelength region 1620-1850 nm, giving a spectral compression factor of up to 19.8-25.9. Owing to the soliton effect, the side lobe level was suppressed to -19.2 to -9.7 dB.

Time-resolved interferometric detection of ultrashort strain solitons in sapphire

Received 12 November 2009; revised manuscript received 23 March 2010; published 13 April 2010We study one-dimensional nonlinear propagation of high-amplitude acoustic waves in sapphire, for varioussample temperatures, sample thicknesses, and pump fluences. Strain waves are generated in a 100-nm-thickchromium film and launched into the sapphire. For temperatures 60 K, damping can be neglected andpropagation is dominated by the nonlinear and dispersive properties of the sapphire substrate. An interfero-metric technique is used to detect the wave on an epitaxially grown 20-nm-thick Cr film at the opposite sideof the sample. At the lowest temperature of 18 K, a train of up to seven solitons is detected in sapphire for apump fluence of 11 mJ/cm

The influence of higher-order effects on the transmission performances of the ultra-short soliton pulses and its suppression method

Under the condition of the higher order effects, a propagation equation is established to investigate the way to suppress the soliton self frequency shift and timing jitter in the picosecond and femtosecond soliton communication system using a combined control method of time domain and frequency domain. By the use of the variational approach, the evolution of the chirping Gaussian quasi-soliton pulse is analyzed in the presence of the effects including third order dispersion, intrapulse Raman scattering (IRS), and self steepening. Considering the soliton evolution properties and the mechanism of the timing jitter under the higher-order effects, the combined control method is adopted to eliminate the influence from Raman scattering and self-steepening. The soliton central frequency is stabilized and the timing jitter is suppressed effectively. A 160 Gb/s long-haul soliton transmission system is designed and its performance is numerically simulated. The simulation results are in good agreement with our theoretical analysis.