Zhang Yan-Peng

The Interaction of Peregrine Solitons

We theoretically investigate the interaction of two in-phase and out-of-phase Peregrine solitons in a Kerr nonlinear medium, addressing both the cases of first- and second-order solitons. Upon adjusting the interval between the solitons, their interactions exhibit different properties. If the interval is sufficiently large, two Peregrine solitons will propagate individually and will not interact each other. However, if the interval is not very large, the Peregrine solitons will strongly interact and display varying behavior.

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.

Fourth-Order Spatial Correlation of Thermal Light

We investigate the fourth-order spatial correlation properties of pseudo-thermal light in the photon counting regime, and apply the Klyshko advanced-wave picture to describe the process of four-photon coincidence counting measurement. We deduce the theory of a proof-of-principle four-photon coincidence counting configuration, and find that if the four randomly radiated photons come from the same radiation area and are indistinguishable in principle, the fourth-order correlation of them is 24 times larger than that when four photons come from different radiation areas. In addition, we also show that the higher-order spatial correlation function can be decomposed into multiple lower-order correlation functions, and the contrast and visibility of low-order correlation peaks are less than those of higher orders, while the resolutions all are identical. This study may be useful for better understanding the four-photon interference and multi-channel correlation imaging.

Interplay of Coexisting Odd-Order Wave Mixings in a Five-Level Atomic System

We experimentally investigate the interplay between two coexisting six-wave mixing (SWM) signals and the interference between coexisting four-wave mixing (FWM) and SWM signals in a five-level atomic system of 85Rb. When two electromagnetically induced transparency windows gradually overlap in frequency, the competition between these two SWM signals arises. Moreover, we report the experimental result which shows that the temporal interference with femtosecond time scales between FWM and SWM signals.

Wavelength dependence four-wave mixing spectroscopy in a micrometric atomic vapour

This paper presents a theoretical study of wavelength dependence four-wave-mixing (FWM) spectroscopy in a micrometric thin atomic vapour. It compares three cases termed as mismatched case I, matched case and mismatched case II for the probe wavelength less, equal and greater than the pump wavelength respectively. It finds that Dicke-narrowing can overcome width broadening induced by Doppler effects and polarisation interference of thermal atoms, and high resolution FWM spectra can be achieved both in matched and mismatched wavelength for many cases. It also finds that the magnitude of the FWM signal can be dramatically modified to be suppressed or to be enhanced in comparison with that of matched wavelength in mismatched case I or II. The width narrowing and the magnitude suppression or enhancement can be demonstrated by considering enhanced contribution of slow atoms induced by atom-wall collision and transient effect of atom-light interaction in a micrometric thin vapour.

Spatial Splitting and Intensity Suppression of Four-Wave Mixing in V-Type Three-Level Atomic System

We illustrate our experimental observation of coexisting the controllable spatial splitting and intensity suppression of four-wave mixing (FWM) beam in a V-type three-level atomic system. The peak number and separation distance of the FWM beam are controlled by the intensities and frequencies of the laser beams, as well as atomic density.

Visibility and Resolution Enhancement of Fourth-Order Ghost Interference with Thermal Light

A scheme for fourth-order double-slit ghost interference with a pseudo-thermal light source is proposed. It is shown that not only can the visibility be dramatically enhanced compared to the third-order case, but also higher resolution is demonstrated if we scan two of three reference detectors in opposite directions with the same speed, meanwhile another two in identical directions where the speed of one reference detector is twice the other. The results show that the visibility and resolution improvement of the fourth-order ghost interference fringe can be applied to the N th-order ghost imaging.

Stop Band Gap in Periodic Layers of Confined Atomic Vapor/Dielectric Medium

A stop band gap is predicted in periodic layers of a confined atomic vapor/dielectric medium. Reflection and transmission profile of the layers over the band gap can be dramatically modified by the confined atoms and the number of layer periods. These gap and line features can be ascribed to the enhanced contribution of slow atoms induced by atom-wall collision, transient behavior of atom-light interaction and Fabry—Perot effects in a thermal confined atomic system.

Enhancement and suppression of spatial splitting four-wave mixing in atomic medium

We experimentally report on the evolution from singly-dressed to doubly-dressed four-wave mixing (FWM) process by controlling the powers of the probe, the pump and the dressing fields respectively. The differences in the enhancement and the suppression of FWM signal between the two-level and cascade three-level atomic systems are observed and explained by the multi-dressed effect theoretically. Both the x direction and the y direction spatial splittings of the degenerate-FWM (DWFM) beams are obtained. We also investigate the switch between the enhancement and the suppression of the DWFM signals and between its spatial splittings in x direction and y direction. The spatial splittings in x direction and y direction can be controlled by the relative position and the intensity of the involved laser beams. Such a study can be useful for optimizing the efficiency of the FWM process and providing potential applications in spatial signal processing.

Polarized Spatial Splitting of Four-Wave Mixing Signal in Multi-Level Atomic Systems

We illustrate our experimental observation of the periodic changes of spatial splitting of the generated four-wave mixing (FWM) signal induced by different polarization states of one of the dressing beams. It is pointed out that the changes of intensity of the dressing beam and the FWM signal have influences on the spatial splitting and their influences compete with each other. The differences between p- and s-polarized FWM beams are demonstrated. The influences of the dressing beams, which lead to the larger spatial splitting with different polarization states or frequency detuning, are observed as well.