Spontaneously Generated Coherence Research Articles

Role of incoherent pumping field on control of optical bistability in a closed three-level ladder atomic system

In this paper, we analyze the role of incoherent pumping field on the control of optical bistability (OB) via the spontaneously generated coherence (SGC) and relative phase between laser fields in a closed three-level ladder-type atomic system. It is shown that in the presence of incoherent pumping field, the influences of the SGC and the relative phase of the OB behavior become more effective. Simultaneously, the threshold intensity and width of the OB reduce significantly when the incoherent pumping rate increases.

Sub-Doppler laser cooling via spontaneous generated coherence

We propose a system of four-level atoms which can generate a sub-Doppler cooling in the presence of quantum interference effects. The atom is modeled as a double -type system where dipole-allowed transitions are correlated through the spontaneously generated coherence (SGC). We will show that the including of such interference effects created by spontaneous emission gives rise to a cooling mechanism in which the lowest achievable temperatures approach the single-photon recoil limit. Indeed, this mechanism benefits from the features generated by the phenomenon of SGC-induced electromagnetically induced transparency; in the regime of weak coupling fields, atoms can be subject to a strong radiation pressure force, allowing them to be cooled to near, and even below, the recoil temperature.

Orbital angular momentum transfer via spontaneously generated coherence

We study the orbital angular momentum (OAM) transfer from a weak Laguerre–Gaussian (LG) field to a weak plane wave in two closed-loop three-level V-type atomic systems. In the first scheme, the atomic system has two non-degenerate upper levels where the corresponding transition is excited by a microwave plane wave. It is analytically shown that the microwave field induces an OAM transfer from an LG field to a generated third field. It is demonstrated that the efficiency of the OAM transfer decreases when the thermal velocity distribution of atoms is considered. In the second scheme, we consider a three-level V-type atomic system with two near-degenerate excited states and study the effect of the quantum interference due to the spontaneous emission on the OAM transfer. It is found that spontaneously generated coherence (SGC) induces the OAM transfer from the LG field to the weak planar field, and the OAM transfer does not occur in the absence of the SGC. The suggested models offer a rather simple method for the OAM transfer that can be used in quantum information processing and data storage.

Comparative Study of Light Manipulation in Three-Level Systems Via Spontaneously Generated Coherence and Relative Phase of Laser Fields**Supported by Vietnamese Ministry of Science and Technology under Grant No. DTDLCN.17/17

We present a comparative study of the control of group velocity in three-level atomic systems including Λ-, Ladder-, and V-types via spontaneously generated coherence (SGC) and relative phase of laser fields. In the steady regime, expressions of group index are derived as an analytical function of controllable parameters related to SGC and relative phase. It is shown that the group velocity can be further slowed down or speeded up under SGC in which modifications of group velocity due to the SGC in Λ- and V-systems are stronger than that in Ladder-system. In particular, when interference strength of SGC p increases from 0.7 to 1.0, the light propagation is switched from superluminal to subluminal modes (for Λ- and Ladder-systems) or from subluminal to superluminal modes (for V-system). In the presence of relative phase, the group velocity changes between subluminal and superluminal modes with a period of 2π. In resonant region, the largest positive value of group index reaches at the relative phase φ = π while the largest negative value of group index reaches at φ = 0 and 2π for the Λ- and Ladder-systems, otherwise, for the V-system the largest positive group index occurs at φ = 0 and 2π, and the largest negative group index occurs at φ = π.

Phase dependent Kerr nonlinearity via quantum interference

The first- and third-order susceptibilities of a five-level K-type atomic system with an upper V subsystem connected to a lower Λ subsystem are investigated. An enhanced Kerr nonlinearity accompanied by suppressed linear absorption is achieved just by tuning the intensity and the detuning of coupling laser fields. The effect of spontaneously generated coherence (SGC) on Kerr nonlinearity in such atomic system is then introduced. It is found that in the presence of SGC, the nonlinear response of the system depends on the relative phase of the applied fields.

Enhancement of Goos–Hänchen shifts due to spontaneously generated coherence in a four-level Rydberg atom

The impact of spontaneously generated coherence (SGC) on the Goos–Hänchen (GH) shifts of transmitted and reflected light beams from a cavity with a four-level rubidium atom with a Rydberg state are discussed. Using the quantum mechanical density matrix method, we first discuss the absorption and dispersion properties of the medium, then analyze the GH shifts of transmitted and reflected light beams, respectively. We find that quantum interference from SGC can modify the absorption–dispersion properties, which leads to enhancement in GH shifts in transmitted and reflected light beams. Moreover, the effects of coupling light and its detuning on the properties of GH shifts have been discussed.

Theoretical Investigation of Optical Bistability and Multistability Via Spontaneously Generated Coherence in Four-Level Rydberg Atoms

In this paper, we have suggested a configuration based on Rydberg atoms for adjusting properties of optical bistability (OB) and optical multistability (OM) via spontaneously generated coherence (SGC) in a unidirectional ring cavity. The Rydberg atoms consist of four energy levels interacts by a weak probe and a strong coupling fields, respectively. We have found that due to presence of SGC, threshold of OB and OM can be controlled when the strong light coupled the intermediate levels to the Rydberg state.

Pulse propagation in an atomic medium under spontaneously generated coherence, incoherent pumping, and relative laser phase

Influences of spontaneously generated coherence (SGC) and relative phase of laser fields on a probe laser pulse propagating in a three-level cascade atomic medium under incoherent pumping and electromagnetically induced transparency (EIT) are studied theoretically. It is shown that the leading edge of the pulse oscillates during its propagation. Furthermore, the oscillating magnitude is enhanced by growing SGC, however, it can be depressed by choosing a suitable relative phase between the laser fields. Indeed, the probe pulse depends sensitively on the relative phase with a period of 2 π in which it oscillates strongest at ϕ=0, π and 2 π; whereas it is unchanged at ϕ=π∕2 and 3π/2. On the other hand, the influences of SGC and the relative phase on the pulse envelope are more effective as growing the incoherent pumping rate.

Two-dimensional atom localization based on coherent field controlling in a five-level M-type atomic system.

We study two-dimensional sub-wavelength atom localization based on the microwave coupling field controlling and spontaneously generated coherence (SGC) effect. For a five-level M-type atom, introducing a microwave coupling field between two upper levels and considering the quantum interference between two transitions from two upper levels to lower levels, the analytical expression of conditional position probability (CPP) distribution is obtained using the iterative method. The influence of the detuning of a spontaneously emitted photon, Rabi frequency of the microwave field, and the SGC effect on the CPP are discussed. The two-dimensional sub-half-wavelength atom localization with high-precision and high spatial resolution is achieved by adjusting the detuning and the Rabi frequency, where the atom can be localized in a region smaller thanλ/10×λ/10. The spatial resolution is improved significantly compared with the case without the microwave field.

Phase-sensitive Kerr nonlinearity of V-type atoms-doped dielectric slab

We investigate the linear and nonlinear dispersion and absorption properties of a weak probe field in a slab doped with V-type atoms. The effect of relative phase between applied fields on linear and nonlinear dispersion and absorption is discussed. It is demonstrated that the system is phase-sensitive when spontaneously generated coherence (SGC) exists. The effects of coupling field intensity, incoherent pump, and phase difference between probe and coupling fields on Kerr nonlinearity are also presented.

Generation of one-way Einstein–Podolsky–Rosen steering using interference-controlled asymmetric dissipation process

We show that one-way Einstein–Podolsky–Rosen (EPR) steering effects can be generated via the asymmetric dissipation scheme induced by the spontaneously generated coherence (SGC) in a resonantly driven V-type atomic system. According to the dressed atomic states and Bogoliubov transformation, we find that there exist two identical dissipation channels being responsible for the appearance of entanglement and symmetric two-way steering effects in the absence of SGC effect. More interestingly, the one-way EPR steering effect occurs when the population differences between the dressed states are prominently modified by the SGC effect. As a consequence, the symmetry of the two dissipation channels is broken by the quantum interference, leading to the generation of one-way EPR steering effect.

Multiple spontaneously generated coherence and phase control of optical bistability and multistability in a tripod four-level atomic medium.

Optical bistability (OB) and optical multistability (OM) behaviors induced by multiple spontaneously generated coherence (SGC) are investigated theoretically in a tripod four-level atomic scheme. It is found that OB or OM is sensitive to the SGC effects, and the thresholds of OB can be controlled via changing the strength of multiple SGC or the relative phases of the applied fields. In addition, we can switch OB to OM by adjusting the twofold relative phases of the applied fields or vice versa.

Cavity electromagnetically induced transparency via spontaneously generated coherence

A four-level N-type atomic ensemble enclosed in a cavity is revisited to investigate the influence of spontaneous generated coherence (SGC) on transmission features of weak probe light field. A weak probe field is propagating through the cavity where each atom inside the cavity follows four-level N-type atom-field configuration of rubidium () atom. We use input–output theory and study the interaction of atomic ensemble and three cavity fields which are coupled to the same cavity mode. A SGC affects the transmission properties of weak probe light field due to which a transparency window (cavity EIT) appears. At resonance condition the transparency window increases with increasing the SGC in the system. We also studied the influence of the SGC on group delay and investigated magnitude enhancement of group delay for the maximum SGC in the system.

Localization of cold [formula omitted] atom simulated by a three-level quantum system within half-wavelength domain

Simulating the cold R87b atom with a three-level quantum system interacting with two orthogonal standing-wave fields, the localization within half-wavelength domain in the x-y plane is achieved by monitoring the probe absorption. Within the half-wavelength domain, the single absorption peak increases from 0.2 to 1.0 via the spontaneously generated coherence (SGC), while the diameters of the single absorption peaks are diminished by the increasing incoherent pumping field. Our scheme provides the flexible parameters manipulating manner for the localization of cold R87b atom.

Dynamically controlled optical nonreciprocity of a double-ladder system with spontaneously generated coherence in moving atomic optical lattice**Project supported by the National Natural Science Foundation of China (Grant Nos. 11347137, 11247201, and 11247005) and the Twelfth Five-year Program for Science and Technology of Education Department of Jilin Province, China (Grant No. 20150215).

A four-level double-ladder cold atoms system with spontaneously generated coherence trapped in a moving optical lattice is explored to achieve optical nonreciprocity. When spontaneously generated coherence (SGC) is present, the remarkable contrast optical nonreciprocity of light transmission and reflection can be generated at each induced photonic bandgap in the optical lattice with a velocity of a few m/s. However, when the SGC effect is absent, the optical nonreciprocity becomes weak or even vanishing due to the strong absorption. It is found that the optical nonreciprocity is related to the asymmetric Doppler effect in transmission and reflection, meanwhile the degree and position of optical nonreciprocity can be tuned by the SGC effect and the Rabi frequency of the trigger field.

Dual peaks evolving into a single-peak for sub-wavelength 2-D atom localization in a V-type atomic system

The atom localization of a V-type atomic system is discussed by the detunings associated with the probe and the two orthogonal standing-wave fields, and by the spontaneously generated coherence (SGC). Within the half-wavelength domain in the 2-dimensional (2-D) plane, the atom localization depicted by the probe dual absorption peaks is achieved when the detunings are tuned. However, the dual peaks change into a single-peak when the SGC arises. The single-peak 2-D localization demonstrated the advantage for atom localization achieved by the flexible manipulating parameters in our scheme.

Probe gain via four-wave mixing based on spontaneously generated coherence**Project supported by the Natural Science Foundation of Hainan Province, China (Grant Nos. 20151005, 20151015, and 20161006), the National Natural Science Foundation of China (Grant Nos. 11247005, 51262007, 11501153, and 41564006), the Postdoctoral Scientific Research Program of Jilin Province, China (Grant No. RB201330), the Project Sponsored by Science Research Foundation for

We have studied the probe gain via a double-Λ atomic system with a pair of closely lying lower levels in the presence of two probe and two coherent pump fields. The inversionless gain can be realized by using nondegenerate four-wave mixing under the condition of spontaneously generated coherence (SGC) owing to near-degenerate lower levels. Note that by using SGC, two probe fields can be amplified with more remarkable amplitudes, and the gain spectra of an extremely narrow linewidth can be obtained. Last but not least, our results show that the probe gain is quite sensitive to relative phases due to the SGC presence which allows one to modulate the gain spectra periodically by phase modulation, and can also be influenced by all laser field intensities and frequencies, and the angles between dipole elements.

All-optical switching in an open V-type atomic system

In this paper, the optical bistability (OB) and absorption properties of a weak probe field in an open V-type three-level atomic system have been investigated. We found that the OB threshold could be reduced via spontaneously generated coherence (SGC), coherent and incoherent pump fields, atomic injection, and exit rates. We also found that the threshold intensity of OB in an open system was less than that in the closed system. The all-optical switching due to the OB has also been discussed.

Giant gain from spontaneously generated coherence in Y-type double quantum dot structure

A theoretical model was presented for linear susceptibility using density matrix theory for Y-configuration of double quantum dots (QDs) system including spontaneously generated coherence (SGC). Two SGC components are included for this system: V, and Λ subsystems. It is shown that at high V-component, the system have a giga gain. At low Λ-system component; it is possible to controls the light speed between superluminal and subluminal using one parameter by increasing SGC component of the V-system. This have applications in quantum information storage and spatially-varying temporal clock.

High-precision three-dimensional atom localization via three-wave mixing in V-type three-level atoms

We propose a scheme for realizing high-precision three-dimensional (3D) atom localization by using V-type three-level atoms in which atoms interact with a weak probe field, a weak control field together with three mutually perpendicular standing-wave fields. Our numerical results show that the precision of 3D atom localization in volumes can be improved via three-wave mixing (TWM) in the presence of the control switch field but made instead to be reduced when the TWM channel is off in absence of the switch field. As a result, assisting with TWM, a single position information of the atom in the 3D space can be achieved, and the atom can be localized in volumes that are substantially smaller than a cubic optical wavelength. The effect of spontaneously generated coherence (SGC) as well as the relative phase of the applied fields on the precision of 3D atom localization are also discussed.