Li Yuanyuan

The scattering states of the generalized Hulthén potential with an improved new approximate scheme for the centrifugal term

This paper finds the approximate analytical scattering state solutions of the arbitrary 1-wave Schrodinger equation for the generalized Hulthen potential by taking an improved new approximate scheme for the centrifugal term. The normalized analytical radial wave functions of the l-wave Schrodinger equation for the generalized Hulthen potential are presented and the corresponding calculation formula of phase shifts is derived. Some useful figures are plotted to show the improved accuracy of the obtained results and two special cases for the standard Hulthen potential and Woods–Saxon potential are also studied briefly.

Enhancement and Suppression of Four-Wave Mixing in a Four-Level Atomic System

We report observations of the enhancement and suppression of four-wave mixing (FWM) in an electromagnetically induced transparency window in a Y-type 85Rb atomic system. The results show the evolution of the dressed effects (from pure enhancement to partial enhancement/suppression, and finally into pure suppression) in the degenerate-FWM processes. Moreover, we use the perturbation chain method to describe the FWM process. Finally, we observe the polarization dependence of the enhancement and suppression of the FWM signal.

High-Power and High-Efficiency Operation of Terahertz Quantum Cascade Lasers at 3.3 THz

A high-power and high-efficiency GaAs/AlGaAs-based terahertz (THz) quantum cascade laser structure emitting at 3.3 THz is presented. The structure is based on a hybrid bound-to-continuum transition and resonant-phonon extraction active region combined with a semi-insulating surface-plasmon waveguide. By optimizing material structure and device processing, the peak optical output power of 758 mW with a threshold current density of 120 A/cm2 and a wall-plug efficiency of 0.92% at 10K and 404mW at 77K are obtained in pulsed operation. The maximum operating temperature is as high as 115 K. In the cw mode, a record optical output power of 160 mW with a threshold current density of 178 A/cm2 and a wall-plug efficiency of 1.32% is achieved at 10 K.

Selective reflection combined with Fabry–Perot effects from two-level atoms confined between two dielectric walls

The coefficient of selective reflection at oblique incidence from two-level atoms confined between two dielectric walls is calculated in this paper. It is found to be related to the transient behaviour of atoms after colliding with the wall and the distribution of the field inside the vapour corresponds to L/λ, with L the thickness of the film and λ the incident wavelength. We find that the sub-Doppler structure is manifest both for normal incidence and small angle oblique incidence. It is feasible to detect the real part of selective reflection in several cases that have not been achieved before.

Phase dispersion of Raman and Rayleigh-enhanced four-wave mixings in femtosecond polarization beats

Based on color-locking noisy field correlation in three Markovian stochastic models, phase dispersions of the Raman- and Rayleigh-enhanced four-wave mixing (FWM) have been investigated. The phase dispersions are modified by both linewidth and time delay for negative time delay, but only by linewidth for positive time delay. Moreover, the results under narrowband condition are close to the nonmodified nonlinear dispersion and absorption of the material. Homodyne and heterodyne detections of the Raman, the Rayleigh and the mixing femtosecond difference-frequency polarization beats have also been investigated, separately.

Competition between dispersion and absorption of doubly-dressed four-wave mixing and dressed six-wave mixing

We study the competition between dispersion and absorption of doubly-dressed four-wave mixing (DDFWM) and dressed six-wave mixing. In the case of weak coupling fields limit, we find DDFWM signal is affected by destructive interference between four-wave mixing(FWM) and six-wave mixing as well as constructive interference between FWM and eight-wave mixing. By analysing the difference between two kinds of doubly dressing mechanisms (parallel cascade and nested cascade) in this opening five-level system, we can further understand the generated high-order nonlinear optical signal dressed by multi-fields.

Interaction of Triply-Dressing Electromagnetically Induced Transparency in Five-level Folding Atomic System

We consider a five-level atomic folding system, which involve two kinds of dressing mechanisms (the nested-cascade and the sequential-cascade) in interaction of three-dressing fields, the numerical results show that three-dressing fields are interchangeable under certain conditions, which can be considered as two four-level sub-system configurations (a nested-cascade N configuration and a sequential-cascade inverted-Y configuration).

Coherent Phase Control of Ultrafast Polarization Beats in Reverse V-Type Three-Level System

We investigate the third-order nonlinear absorption and dispersion of femto- and atto-second polarization beats between the one-photon degenerate four-wave mixing process and the two-photon nondegenerate four-wave mixing process in the pure homogeneously-broadened reverse V-three-level using twin noisy fields. The third-order nonlinear response can be controlled and modified by the colour-locked correlation of twin noisy fields. Most importantly, the coherent phase control in optical heterodyne detection for studying the phase dispersion of the third-order susceptibility is demonstrated. The radiation-matter detuning oscillation is also considered in the frequency domain.

Six-wave mixing phase-dispersion by optical heterodyne detection in dressed reverse N-type four-level system

We have investigated the dressed effects of non-degenerate four-wave mixing (NDFWM) and demonstrated a phase-sensitive method of studying the fifth-order nonlinear susceptibility due to atomic coherence in RN-type four-level system. In the presence of a strong coupling field, NDFWM spectrum exhibits Autler–Townes splitting, accompanied by either suppression or enhancement of the NDFWM signal, which is directly related to the competition between the absorption and dispersion contributions. The heterodyne-detected nonlinear absorption and dispersion of six-wave mixing signal in the RN-type system show that the hybrid radiation-matter detuning damping oscillation is in the THz range and can be controlled and modified through the colour-locked correlation of twin noisy fields.