arXiv subjects

Guoxiang Huang

Publications and source records attributed to Guoxiang Huang.

At least 55 records · Page 3Linked to original sources

arXiv2014

Ultraslow Optical Solitons and Their Storage and Retrieval in an Ultracold Ladder-Type Atomic System

We propose a scheme to obtain stable nonlinear optical pulses and realize their storage and retrieval in an ultracold ladder-type three-level atomic gas via electromagnetically induced transparency. Based on Maxwell-Bloch equations we derive a nonlinear equation governing the evolution of probe field envelope, and show that optical solitons with ultraslow propagating velocity and extremely low generation power can be created in the system. Furthermore, we demonstrate that such ultraslow optical solitons can be stored and retrieved by switching off and on a control field. Due to the balance between dispersion and nonlinearity, the ultraslow optical solitons are robust during propagation, and hence their storage and retrieval are more desirable than that of linear optical pulses. This raises the possibility of realizing the storage and retrieval of light and quantum information by using solitonic pulses.

physics.optics↗

arXiv2014

Guiding ultraslow weak-light bullets with Airy beams in a coherent atomic system

We investigate the possibility of guiding stable ultraslow weak-light bullets by using Airy beams in a cold, lifetime-broadened four-level atomic system via electromagnetically induced transparency (EIT). We show that under EIT condition the light bullet with ultraslow propagating velocity and extremely low generation power formed by the balance between diffraction and nonlinearity in the probe field can be not only stabilized but also steered by the assisted field. In particular, when the assisted field is taken to be an Airy beam, the light bullet can be trapped into the main lobe of the Airy beam, propagate ultraslowly in longitudinal direction, accelerate in transverse directions, and move along a parabolic trajectory. We further show that the light bullet can bypass an obstacle when guided by two sequential Airy beams. A technique for generating ultraslow helical weak-light bullets is also proposed.

physics.optics↗

arXiv2014

PT-symmetric coupler with a coupling defect: soliton interaction with exceptional point

We study interaction of a soliton in a parity-time (PT) symmetric coupler which has local perturbation of the coupling constant. Such a defect does not change the PT-symmetry of the system, but locally can achieve the exceptional point. We found that the symmetric solitons after interaction with the defect either transform into breathers or blow up. The dynamics of anti-symmetric solitons is more complex, showing domains of successive broadening of the beam and of the beam splitting in two outwards propagating solitons, in addition to the single breather generation and blow up. All the effects are preserved when the coupling strength in the center of the defect deviates from the exceptional point. If the coupling is strong enough the only observable outcome of the soliton-defect interaction is the generation of the breather.

physics.optics↗

arXiv2014

Ultraslow Helical Optical Bullets and Their Acceleration in Magneto-Optically Controlled Coherent Atomic Media

We propose a scheme to produce ultraslow (3+1)-dimensional helical optical solitons, alias helical optical bullets, in a resonant three-level $Λ$-type atomic system via quantum coherence. We show that, due to the effect of electromagnetically induced transparency, the helical optical bullets can propagate with an ultraslow velocity up to $10^{-5}$ $c$ ($c$ is the light speed in vacuum) in longitudinal direction and a slow rotational motion (with velocity $10^{-7}$ $c$) in transverse directions. The generation power of such optical bullets can be lowered to microwatt, and their stability can be achieved by using a Bessel optical lattice potential formed by a far-detuned laser field. We also show that the transverse rotational motion of the optical bullets can be accelerated by applying a time-dependent Stern-Gerlach magnetic field. Because of the untraslow velocity in the longitudinal direction, a significant acceleration of the rotational motion of optical bullets may be observed for a very short medium length.

physics.optics↗

arXiv2014

Slow-light Airy wave packets and their active control via electromagnetically induced transparency

We propose a scheme to generate (3+1)-dimensional slow-light Airy wave packets in a resonant $Λ$-type three-level atomic gas via electromagnetically induced transparency. We show that in the absence of dispersion the Airy wave packets formed by a probe field consist of two Airy wave packets accelerated in transverse directions and a longitudinal Gaussian pulse with a constant propagating velocity lowered to $10^{-5}\,c$ ($c$ is the light speed in vacuum). We also show that in the presence of dispersion it is possible to generate another type of slow-light Airy wave packets consisting of two Airy beams in transverse directions and an Airy wave packet in the longitudinal direction. In this case, the longitudinal velocity of the Airy wave packet can be further reduced during propagation. Additionally, we further show that the transverse accelerations (or bending) of the both types of slow-light Airy wave packets can be completely eliminated and the motional trajectories of them can be actively manipulated and controlled by using a Stern-Gerlach gradient magnetic field.

physics.optics↗

arXiv2013

PT Symmetry via Electromagnetically Induced Transparency

We propose a scheme to realize parity-time (PT) symmetry via electromagnetically induced transparency (EIT). The system we consider is an ensemble of cold four-level atoms with an EIT core. We show that the cross-phase modulation contributed by an assisted field, the optical lattice potential provided by a far-detuned laser field, and the optical gain resulted from an incoherent pumping can be used to construct a PT-symmetric complex optical potential for probe field propagation in a controllable way. Comparing with previous study, the present scheme uses only a single atomic species and hence is easy for the physical realization of PT-symmetric Hamiltonian via atomic coherence.

quant-ph↗

arXiv2013

Crossover from Electromagnetically Induced Transparency to Autler-Townes Splitting in Open Ladder Systems with Doppler Broadening

We propose a general theoretical scheme to investigate the crossover from electromagnetically induced transparency (EIT) to Autler-Townes splitting (ATS) in open ladder-type atomic and molecular systems with Doppler broadening. We show that when the wavenumber ratio $k_c/k_p\approx -1$, EIT, ATS, and EIT-ATS crossover exist for both ladder-I and ladder-II systems, where $k_c$ ($k_p$) is the wavenumber of control (probe) field. Furthermore, when $k_c/k_p$ is far from $-1$ EIT can occur but ATS is destroyed if the upper state of the ladder-I system is a Rydberg state. In addition, ATS exists but EIT is not possible if the control field used to couple the two lower states of the ladder-II system is a microwave field. The theoretical scheme developed here can be applied to atoms, molecules, and other systems (including Na$_2$ molecules, and Rydberg atoms), and the results obtained may have practical applications in optical information processing and transformation.

physics.optics↗

arXiv2013

Tunable nonlinear PT-symmetric defect modes with an atomic cell

We propose a scheme of creating a tunable highly nonlinear defect in a one-dimensional photonic crystal. The defect consists of an atomic cell filled in with two isotopes of three-level atoms. The probe-field refractive index of the defect can be made parity-time (PT) symmetric, which is achieved by proper combination of a control field and of Stark shifts induced by a far-off-resonance field. In the PT-symmetric system families of stable nonlinear defect modes can be formed by the probe field.

physics.optics↗

arXiv2013

Crossover from Electromagnetically Induced Transparency to Autler-Townes Splitting in Open V-Type Molecular Systems

We investigate electromagnetically induced transparency (EIT) and Autler-Townes splitting(ATS) in an open V-type molecular system. Through detailed analytical calculations on the absorption spectrum of probe laser field by using residue theorem and spectrum decomposition, we find that EIT may occur and there exists a crossover from EIT to ATS (i.e. EIT-ATS crossover) for hot molecules. However, there is no EIT and hence no EIT-ATS crossover for cold molecules. Furthermore, we prove that for hot molecules EIT is allowed even for a counter-propagating configuration. We provide explicit formulas of EIT conditions and widths of EIT transparency windows of probe field when hot molecules work in co-propagating and counter-propagating configurations, respectively. Our theoretical result agrees well with the recent experimental one reported by Lazoudis et al. [Phys. Rev. A 83, 063419 (2011)].

physics.optics↗

arXiv2012

Analytical approach on linear and nonlinear pulse propagations in an open Lambda-type molecular system with Doppler broadening

We develop a systematic analytical approach on linear and nonlinear pulse propagations in an open Lambda-type molecular system with Doppler broadening. In linear case, by using residue theorem and a spectrum decomposition method, we prove that there exists a crossover from electromagnetically induced transparency (EIT) to Autler-Townes splitting (ATS) for co-propagating configuration of probe and control fields. However, there is no EIT and hence no EIT-ATS crossover for counter-propagating configuration. We give various explicit formulas, including probe-field spectrum decomposition, EIT condition, width of EIT transparency window, as well as a comparison with the result of cold molecules. Our analytical result agrees well with the experimental one reported recently by A. Lazoudis et al. [Phys. Rev.A82, 023812 (2010)]. In nonlinear case, by using the method of multiple-scales, we derive a nonlinear envelope equation for probe-field propagation. We show that stable ultraslow solitons can be realized in the open molecular system.

physics.optics↗

arXiv2012

PT-symmetry with a system of three-level atoms

We show that a vapor of multilevel atoms driven by far-off resonant laser beams, with possibility of interference of two Raman resonances, is highly efficient for creating parity-time (PT) symmetric profiles of the probe-field refractive index, whose real part is symmetric and imaginary part is anti-symmetric in space. The spatial modulation of the susceptibility is achieved by proper combination of standing-wave strong control fields and of Stark shifts induced by a far-off-resonance laser field. As particular examples we explore a mixture of isotopes of Rubidium atoms and design a PT-symmetric lattice and a parabolic refractive index with a linear imaginary part.

physics.optics↗

arXiv2012

Stern-Gerlach Effect of Weak-Light Ultraslow Vector Solitons

We propose a scheme to exhibit Stern-Gerlach (SG) deflection of high-dimensional vector optical soliton (VOS) at weak-light level in a cold atomic gas via electromagnetically induced transparency. We show that the propagating velocity and generation power of such VOS can be reduced to $10^{-6}\,\,c$ ($c$ is light speed in vacuum) and lowered to magnitude of nanowatt, respectively. The stabilization of the VOS may be realized by using an optical lattice formed by a far-detuned laser field, and its trajectory can be deflected significantly by using a SG magnetic field. Deflection angle of the VOS can be of magnitude of $10^{-3}$ rad when propagating several millimeters. Different from atomic SG deflection, deflection angle of the VOS can be distinct for different polarization components and can be manipulated in a controllable way. The results obtained can be described in terms of a SG effect for the VOS with quasispin and effective magnetic moment.

physics.optics↗

arXiv2011

Highly Entangled Photons and Rapidly Responding Polarization Qubit Phase Gates in a Room-Temperature Active Raman Gain Medium

We present a scheme for obtaining entangled photons and quantum phase gates in a room-temperature four-state tripod-type atomic system with two-mode active Raman gain (ARG). We analyze the linear and nonlinear optical response of this ARG system and show that the scheme is fundamentally different from those based on electromagnetically induced transparency and hence can avoid significant probe-field absorption as well as temperature-related Doppler effect. We demonstrate that highly entangled photon pairs can be produced and rapidly responding polarization qubit phase gates can be constructed based on the unique features of enhanced cross-phase modulation and superluminal probe-field propagation of the system.

physics.optics↗

arXiv2011

Linear and Nonlinear Pulse Propagations in Lifetime-Broadened Atomic Media with Spontaneously Generated Coherence

The linear and nonlinear pulse propagations in lifetime-broadened three-state media with spontaneously generated coherence (SGC) are investigated theoretically. Three generic systems of V-, $Λ$-, and $Ξ$-type level configurations are considered and compared. It is shown that in linear propagation regime the SGC in the V-type system can result in a significant change of dispersion and absorption and may be used to completely eliminate the absorption and largely reduce the group velocity of a probe field. However, the SGC has no effect on the dispersion and absorption of the $Λ$- and $Ξ$-type systems. In nonlinear propagation regime, the SGC displays different influences on Kerr nonlinearity for different systems. Specifically, it can enhance the Kerr nonlinearity of the V-type system whereas weaken the Kerr nonlinearity of the $Λ$-type system. Using the SGC, stable optical solitons with ultraslow propagating velocity and very low pump power can be produced in the V-type system by exploiting only one laser field in the system.

physics.optics↗

arXiv2011

Strongly interacting and highly entangled photons in asymmetric quantum well with resonant tunneling

We propose an asymmetric quantum well structure to realize strong interaction between two slow optical pulses. The linear optical properties and nonlinear optical responses associated with cross-Kerr nonlinearity are analyzed. Combining the resonant tunneling and the advantages of inverted-Y type scheme, giant cross-Kerr nonlinearity can be achieved with vanishing absorptions. Based on the unique feature, we demonstrate that highly entangled photons can be produced and photonic controlled phase gate can be constructed. In this construction, the scheme is symmetric for the probe and signal pulses. Consequently, the condition of group velocity matching can be fulfilled by adjusting the initial electron distribution.

physics.optics↗

arXiv2007

Weak-Light Ultraslow Vector Optical Solitons via Electromagnetically Induced Transparency

We propose a scheme to generate temporal vector optical solitons in a lifetime broadened five-state atomic medium via electromagnetically induced transparency. We show that this scheme, which is fundamentally different from the passive one by using optical fibers, is capable of achieving distortion-free vector optical solitons with ultraslow propagating velocity under very weak drive conditions. We demonstrate both analytically and numerically that it is easy to realize Manakov temporal vector solitons by actively manipulating the dispersion and self- and cross-phase modulation effects of the system.

physics.optics↗

arXiv2006

Quantum Depletion of a Soliton Condensate

We present rigorous results on the diagonalization of Bogoliubov Hamilto- nian for a soliton condensate. Using the complete and orthonomalized set of eigenfunction for the Bogoliubov de Gennes equations, we calculate ex- actly the quantum depletion of the condensate and show that two degenerate zero-modes, which originate from a U(1) guage- and a translational-symmetry breaking of the system, induce the quantum diffusion and transverse instabil- ity of the soliton condensate.

cond-mat.other↗

arXiv2006

Three-Way Entanglement and Three-Qubit Phase Gate Based on a Coherent Six-Level Atomic System

We analyze the nonlinear optical response of a six-level atomic system under a configuration of electromagnetically induced transparency. The giant fifth-order nonlinearity generated in such a system with a relatively large cross-phase modulation effect can produce efficient three-way entanglement and may be used for realizing a three-qubit quantum phase gate. We demonstrate that such phase gate can be transferred to a Toffoli gate, facilitating practical applications in quantum information and computation.

quant-ph↗