Biomedical subjects

Guoxiang Huang

Publications and source records attributed to Guoxiang Huang.

7 recordsLinked to original sources

PubMed2006

Stable high-dimensional spatial weak-light solitons in a resonant three-state atomic system.

We study the formation of a nonlinear localized high-dimensional optical beam in a lifetime-broadened three-state atomic system. We show that stable high-dimensional spatial optical solitons with extremely weak-light intensity can occur in such a highly resonant medium through a mechanism of electromagnetically induced transparency. We demonstrate that the interaction between two high-dimensional spatial optical solitons displays interesting properties and these solitons can be easily controlled by manipulating the coupling optical field of the system.

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PubMed2006

Formation and propagation of coupled ultraslow optical soliton pairs in a cold three-state double- system.

We investigate the simultaneous formation and propagation of coupled ultraslow optical soliton pairs in a cold, lifetime-broadened three-state double-Lambda atomic system. Starting from the equations of motion of atomic response and two-mode probe-control electromagnetic fields, we derive coupled nonlinear Schrödinger equations that govern the nonlinear evolution of the envelopes of the probe fields in this four-wave mixing scheme by means of the standard method of multiple scales. We demonstrate that for weak probe fields and with suitable operation conditions, a pair of coupled optical solitons moving with remarkably slow propagating velocity can be established in such a highly resonant atomic medium. The key elements to such a shape preserving, well matched yet interacting soliton pair is the balance between dispersion effect and self- and cross-phase modulation effects of the system.

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PubMed2006

Generalized nonlinear Schrödinger equation and ultraslow optical solitons in a cold four-state atomic system.

We investigate the influence of high-order dispersion and nonlinearity on the propagation of ultraslow optical solitons in a lifetime broadened four-state atomic system under a Raman excitation. Using a standard method of multiple-scales we derive a generalized nonlinear Schrödinger equation and show that for realistic physical parameters and at the pulse duration of 10(-6)s, the effects of third-order linear dispersion, nonlinear dispersion, and delay in nonlinear refractive index can be significant and may not be considered as perturbations. We provide exact soliton solutions for the generalized nonlinear Schrödinger equation and demonstrate that optical solitons obtained may still have ultraslow propagating velocity. Numerical simulations on the stability and interaction of these ultraslow optical solitons in the presence of linear and differential absorptions are also presented.

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PubMed2005

Formation and propagation of matched and coupled ultraslow optical soliton pairs in a four-level double- system.

We investigate the simultaneous formation and stable propagation of ultraslow optical soliton pairs in a lifetime broadened four-state atomic system under double-Lambda excitation with large one- and two-photon detunings. We show that detrimental probe field distortions due to strong dispersion effects under weak driving conditions can be well balanced by self- and cross-phase modulation effects, leading to a pair of temporal, group velocity, and amplitude matched ultraslow optical solitons of different frequencies.

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PubMed2005

Davey-Stewartson description of two-dimensional nonlinear excitations in Bose-Einstein condensates.

We study nonlinear modulation of collective excitations in disk-shaped Bose-Einstein condensates with a repulsive interatomic interaction. Using a method of multiple scales we show that the nonlinear evolution of a wave packet, formed by the superposition of short-wavelength excitations, and a long-wavelength mean field, generated by the self-interaction of the wave packet, are governed by Davey-Stewartson (DS) equations. Consequently, two-dimensional soliton (dromion) solutions can develop and propagate. We further derive a set of DS equations with variable coefficients for the situation where a slowly varying trapping potential in transverse directions has been taken into consideration. Finally, the dromion solutions and their stability are investigated by numerical simulations.

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PubMed2005

Dynamics of ultraslow optical solitons in a cold three-state atomic system.

We present a systematic study on the dynamics of a ultraslow optical soliton in a cold, highly resonant three-state atomic system under Raman excitation. Using a method of multiple scales we derive a modified nonlinear Schrödinger equation with high-order corrections that describe effects of linear and differential absorption, nonlinear dispersion, delay response of nonlinear refractive index, diffraction, and third-order dispersion. Taking these effects as perturbations we investigate in detail the evolution of the ultraslow optical soliton using a standard soliton perturbation theory. We show that due to these high-order corrections the ultraslow optical soliton undergoes deformation, change of propagating velocity, and shift of oscillating frequency. In addition, a small radiation superposed by dispersive waves is also generated from the soliton. The results of the present work may provide a guidance that is useful for experimental demonstration of ultraslow optical soliton in cold atomic systems.

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PubMed2004

Second-harmonic generation in optical fibers on a continuous-wave background.

We predict that a different type of second-harmonic generation (SHG) in nonlinear optical fibers is possible for the waves excited from a continuous-wave background. We show that in a normal dispersion regime and near the zero-dispersion point of a single-mode optical fiber the phase-matching condition of the SHG can be satisfied by suitably choosing the wave vectors and frequencies of fundamental and second-harmonic waves. Using a multiscale method the nonlinearly coupled envelope equations for the SHG are derived and their explicit solutions are provided and checked by numerical simulation.

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