Xue-Mei Su

Optical bistability in electromagnetically induced grating

Abstract We explore a new type of optical bistability (OB) based on electromagnetically induced grating (EIG) and discuss the factors that affect the instability of this system. The stability of each branch of the solution is analyzed.

Optical switching based on transparency in a semiconductor double-quantum well

Abstract We propose a scheme for a photon switch in a semiconductor double-quantum well structure by quantum interference in intersubband transitions.

Group velocity control of a light pulse using giant nonlinearities

In this paper, we propose and demonstrate a scheme to enhance nonlinearities of a probe pulse at both cross-phase modulation (XPM) and self-phase modulation (SPM) in a four-level system. Based on standing wave grating generated by counter-propagating resonant signal fields and an additional off-resonant coupling field, a giant nonlinear refractive index of the resonant probe field is obtained with absorption suppressed. Group velocity of the probe pulse can be controlled by both XPM and SPM nonlinearities.

Room-Temperature Steady-State Entanglement in a Four-Mode Optomechanical System*

Stationary entanglement in a four-mode optomechanical system, especially under roomtemperature, is discussed. In this scheme, when the coupling strengths between the two target modes and the mechanical resonator are equal, the results cannot be explained by the Bogoliubov mode- based scheme. This is related to the idea of quantum-mechanics-free subspace, which plays an important role when the thermal noise of the mechanical modes is considered. Significantly prominent steady-state entanglement can be available under room-temperature.

Observation of electromagnetically induced photonic band gaps in hot two-level atoms

In this paper, two-level thermal Cs atoms are used to observe electromagnetically induced photonic band gaps with a strong symmetric and two types of asymmetric standing-wave (SW) driving fields. One main band and two sidebands are measured for the transmitted and reflected spectra. We carry out physical interpretation about the observations in SW-dressed atom picture and employ method of Fourier transformation to solve density-matrix equations for hot two-level system to simulate the experimental results. The numerical analyses are consistent with the experimental observations for properties of electromagnetically induced photonic band gaps.

Single photon transfer controlled by excitation phase in a two-atom cavity system

We investigate the quantum interference effects of single photon transfer in two-atom cavity system caused by external excitation phase. In the proposed system, two identical atoms (with different positions in the optical cavity) are firstly prepared into a timed state by an external single photon field. During the excitation, the atoms grasp different phases which depend on the spatial positions of the atoms in the cavity. Due to strong resonant interaction between two atoms and optical cavity mode the absorbed input photon can be efficiently transferred from the atoms to the resonant cavity mode. We show that the quantum transfer is highly sensitive to the external excitation phases of atoms and it leads to quantum interference effects on the cavity mode excitation. Besides, the quantum transfer is also influenced by the dipole-dipole interaction dependent to the atomic distance. In this system the atomic positions also determine the coupling constants between atoms and cavity mode which causes additional interference effects to the photon exchange between atoms and cavity. Based on the characteristics of excitation phase we find that it is a feasible scheme to generate long-lived dark state and it could be useful for storage and manipulation of single photon fields by controlling the excitation phase.

Narrow dark polariton due to coupled coherence in a quantum well microcavity

A scheme is proposed to obtain slow light in a coulped quantum wells microcavity with tunneling induced transparency between intersubband electronic transitions. Three prolaritons are created by intracavity Fano interference between fundamental mode photon and two quantum oscillators of coherent subband electronic excitations. A narrow middle dark polariton of the three can be produced, which can be used to suppress the line profiles of the transmission or reflection spectra for the incident light. This leads to slow propagation of the incident light in the microcavity. The semiconductor optical microcavity can be an alternative choice of quantum photoelectronic devices in nanoscale.

Enhanced group velocity dispersion and nonlinearity for a weak field using quantum coherence

We propose a scheme in a four level atomic system to enhance group velocity dispersion and nonlinearity for a weak field using photonic bandgap created by quantum coherence with standing fields, where weak probe pulse propagates fast or slowly controlled by interaction between atoms and coherent fields.

Photon switch by Fano interference in a double quantum well structure

In this paper, we demonstrate a weak photon switch by Fano interference in a double quantum well structure. GaAs/AlGaAs and InGaAs/AlAs heterostructures are taken as switch media to show that the weak switch can work at different wavelength by choosing materials and structures. We also estimate the order of the switch power and show that this photon switch by Fano interference in coupled double quantum well structures is a weak optical switch that can be used to realize one optical beam control another beam.