Phase-controlled atom-photon entanglement in a three-level V-type atomic system via spontaneously generated coherence

We investigate the dynamical behavior of the atom-photon entanglement in a V-type three-level quantum system using the atomic reduced entropy. It is shown that an atom and photons are entangled at the steady-state; however disentanglement can also be achieved in an especial condition. It is demonstrated that in the presence of quantum interference induced by spontaneous emission, the reduced entropy and the atom-photon entanglement are phase-dependent. Non-stationary solution is also obtained when the quantum interference due to the spontaneous emission is completely included.Comment: 16 pages, 7 figure

Phase control of electromagnetically induced transparency and its applications to tunable group velocity and atom localization

We show that, by simple modifications of the usual three-level $\Lambda$-type scheme used for obtaining electromagnetically induced transparency (EIT), phase dependence in the response of the atomic medium to a weak probe field can be introduced. This gives rise to phase dependent susceptibility. By properly controlling phase and amplitudes of the drive fields we obtain variety of interesting effects. On one hand we obtain phase control of the group velocity of a probe field passing through medium to the extent that continuous tuning of the group velocity from subluminal to superluminal and back is possible. While on the other hand, by choosing one of the drive fields to be a standing wave field inside a cavity, we obtain sub-wavelength localization of moving atoms passing through the cavity field.Comment: To Appear in SPIE Proceedings Volume 573

Subwavelength atom localization via amplitude and phase control of the absorption spectrum

We propose a scheme for subwavelength localization of an atom conditioned upon the absorption of a weak probe field at a particular frequency. Manipulating atom-field interaction on a certain transition by applying drive fields on nearby coupled transitions leads to interesting effects in the absorption spectrum of the weak probe field. We exploit this fact and employ a four-level system with three driving fields and a weak probe field, where one of the drive fields is a standing-wave field of a cavity. We show that the position of an atom along this standing wave is determined when probe field absorption is measured. We find that absorption of the weak probe field at a certain frequency leads to subwavelength localization of the atom in either of the two half-wavelength regions of the cavity field by appropriate choice of the system parameters. We term this result as sub-half-wavelength localization to contrast it with the usual atom localization result of four peaks spread over one wavelength of the standing wave. We observe two localization peaks in either of the two half-wavelength regions along the cavity axis.Comment: Accepted for publication to Physical Review

Group velocity control in the ultraviolet domain via interacting dark-state resonances

The propagation of a weak probe field in a laser-driven four-level atomic system is investigated. We choose mercury as our model system, where the probe transition is in the ultraviolet region. A high-resolution peak appears in the optical spectra due to the presence of interacting dark resonances. We show that this narrow peak leads to superluminal light propagation with strong absorption, and thus by itself is only of limited interest. But if in addition a weak incoherent pump field is applied to the probe transition, then the peak structure can be changed such that both sub- and superluminal light propagation or a negative group velocity can be achieved without absorption, controlled by the incoherent pumping strength

Phase-sensitive Kerr nonlinearity in a three-level n-doped semiconductor quantum well (SQW)

A three-level n-doped semiconductor quantum well (SQW) based on phase-sensitive Kerr nonlinearity is proposed. The effect of phase difference between applied fields on linear and nonlinear dispersion and absorption is then discussed. It is found that by proper selection of the relative phase of applied fields, the linear and nonlinear absorption converts to linear and nonlinear gain, and simultaneously the Kerr nonlinearity enhances dramatically. Also the impacts of coupling fields intensity on linear and nonlinear absorption and dispersion are discussed

Inversionless light amplification in one-dimensional photonic crystal with a dispersive layer

Probe field amplification through one-dimensional photonic crystal is investigated. Absorption and transmission properties of an incident probe pulse through one-dimensional photonic crystal are controlled by the quantum interference mechanism. It is shown that the quantum interference leads to phase control of the transmission and absorption behavior of a weak probe beam during its propagation through the one-dimensional photonic crystal. We further find that the gain without the population inversion can be achieved in the presence of doped atomic system at defect layer. In addition, the dynamical behavior of the probe field through the proposed medium is discussed, and the switching time of probe absorption to gain (or vice versa) is estimated

Controlling the Goos-Hänchen shift via quantum interference

The behavior of the Goos-Hänchen (GH) shifts of a probe beam reflected from or transmitted through a cavity with a fixed geometrical configuration is theoretically investigated. The effect of quantum interference induced by incoherent pump and spontaneous emission upon the control of GH shifts is then discussed. In addition, the effect of the rate of an incoherent pump field and the intensity of coupling field on the behavior of GH shifts are presented

The effect of spontaneously generated coherence on the Goos-Hänchen shifts behavior

The behavior of the Goos-Hänchen (GH) shifts of a probe beam reflected from or transmitted through a cavity with a fixed geometrical configuration is theoretically investigated. It is shown that in the absence of coherent control fields and just by quantum interference of spontaneous emission, the behavior of GH shift can be controlled

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