Hou Bang-pin

High Refractive Index without Absorption in a Ladder-Type System

A three-level ladder-type system with vacuum-induced coherence and incoherent pumping is studied to obtain a high refractive index without absorption. It is shown that the enhancement of the refractive index without absorption can be accomplished by choosing the proper values of the incoherent pumping, the angle between the two dipole moments, the probe detuning and the relative phase of the two coherent fields.

Dynamical Properties of Two Coupled Dissipative QED Cavities Driven by Coherent Fields

When two identical QED cavities driven by the coherent fields are located in a uniform environment, in addition to dissipation, there appears an indirect coupling between the two cavities induced by the background fields. We investigate the effects of the coherent fields, the dissipation as well as the incoherent coupling on the following dynamical properties of the system: photon transfer, reversible decoherence, and quantum state transfer, etc. We find that the photons in the cavities do not leak completely into the environment due to the collective coupling between the cavities and the enviroment, and the photons are transferred irreversibly from the cavity with more photons to the cavity with less ones due to the incoherent coupling so that they are equally distributed among the two cavities. The coherent field pumping on the two cavities increases the mean photons, complements the revived magnitude of the reversible decoherence, but hinders the quantum state transfer between the two cavities. The above phenomena may find applications in quantum communication and other basic fields.

Local Modulation of Double Electromagnetically Induced Transparency Spectrum

The double electromagnetically induced transparency induced by two coupling fields can be realized in a four-level tripod-type atom. Such double transparency spectra can be locally modulated by using the weak coherent fields to perturb the coupling transitions. These investigations within this scheme can be independent of Doppler broadening by properly orienting these fields.

Exact Solution to Rate Equation with Time-Dependent Coefficients: Its Application in InGaAsP Lasers

By using the algebraic dynamics method, we obtain exact analytical solutions of rate equations with time-dependent coefficients, which might present an effective description of the physical mechanism of the practical semiconductor lasers. Based on the exact solutions, we investigate the dynamic behaviour and the emitted properties of the InGaAsP laser, which has been commonly used in long wavelength optical communication systems. It is found that when the cavity length varies with time exponentially, the output power of the laser will drop and approach its asymptote. When the cavity length is a sinusoid function of time, the intensity of the emitted optical pulses can be controlled by the amplitude of this function.

Exact Solution to Helmholtz Equation for Inhomogeneous Medium: Its Application in Optical Communication

In order to study the capability of amplifying the input optical signal of certain materials, we investigate the Helmholtz equation which describes a system of inhomogeneous media. After exploring its SU(1,1) algebraic structure, we obtain the exact solutions of this Helmholtz equation by means of the algebraic dynamical method. Based on the exact solutions, we analyse the capability of optical amplifiers, which is an important issue in modern optical communication. We take the wave number k0(z) and the expansion coefficient k2(z) to be the trigonometric functions, exponential functions and power functions of variable z, respectively. It is found that the material following the exponential functions is the best one for optical amplifiers.

Analytical Solution and Production of Coherent State of the Generalized Dissipative Two-Mode Optical System

We obtain the analytical solution to the master equation in the photon number representation by using algebraic dynamical method in the nonautonomous case. Based on the solution we find that a two-mode coherent sate can be produced within dissipative background, and the averaged photon number for each mode is related to the damping constant, external field amplitude and coupling constant between two modes.

Reversible Decoherence of a Mesoscopic Superposition Driven by a Time-Dependent External Field

By using the normal-ordering technique in the coherent state representation, we discuss the dynamical evolution of the coherence of a Schrodinger cat state in a high Q cavity coupled to another resonator in the presence of external fields. During the progression of the coherence, we pay particular attention to the effect of the external fields, as well as to the initial phase of the Schrodinger cat state.

Sum and two-atom dipole squeezing in a system of a two-mode vacuum field interacting with two coupled atoms

We discuss the effects of the initial atomic coherent factors (including the phase and the distribution parameter) and the dipole-dipole interaction on the sum and two-atom dipole squeezing in the system. The results show that the maximum squeezing in both cases is determined by the phase and the distribution parameter and the duration of squeezing becomes longer by strengthening the dipole-dipole interaction. In addition, the comparison of the two types of squeezing shows that one type of squeezing is obtained at the expense of increased fluctuations in the other squeezing function.