Jin-Hui Wu

Mitigated Tregs and Augmented Th17 Cells and Cytokines are Associated with Severity of Experimental Autoimmune Neuritis

Experimental autoimmune neuritis (EAN), an animal model of human Guillain–Barré syndrome, has long been considered as a T helper (Th) 1 cell–mediated autoimmune disorder. However, deficiency of IFN‐γ, a signature Th1 cytokine, aggravated EAN, with features of elevated production of IL‐17A, despite an alleviated systemic Th1 immune response. We hypothesized that Th17 cells and their cytokines might play a pathogenic role in EAN. To further clarify the roles of these Th and regulatory T cell (Treg) cytokines in the pathogenesis of EAN and their interrelationship, we investigated the expression of Th1/Th2/Th17/Treg cytokines in EAN in this study. We found that the levels of Th17 cells and IL‐17A in cauda equina (CE)‐infiltrating cells and splenic mononuclear cells (MNCs) as well as in serum paralleled the disease evolution, which increased progressively during the initiation stage and reached higher value at the peak of EAN. The same pattern was also noticed for the expression of IL‐22. The diverse expression profiles of FoxP3, IL‐17 receptors A and C were seen in CE‐infiltrating cells and splenic MNCs in EAN. These findings indicate a major pro‐inflammatory role of Th17 cells and IL‐17A in the pathogenesis of EAN. Therapeutic interventions may be focused upon inhibiting Th17 cells and their cytokines in the early phase of EAN, so as to delay and suppress clinical signs of the disease, which has relevance for future studies on pathogenesis and treatment of GBS in humans.

Controlling the photonic band structure of optically driven cold atoms

An analytical method based on a two-mode approximation is here developed to study the optical response of a periodically modulated medium of ultracold atoms driven into a regime of standing-wave electromagnetically induced transparency. A systematic comparison with the usual approach based on the coupled Maxwell-Liouville equations shows that our method is very accurate in the frequency region of interest. Our method, in particular, explains in a straightforward manner the formation of a well-developed photonic bandgap in the optical Bloch wave vector dispersion. For ultracold 87Rb atoms nearly perfect reflectivity may be attained and a light pulse whose frequency components are contained within the gap is seen to be reflected with little loss and deformation.

Optical nonreciprocity of cold atom Bragg mirrors in motion.

Reciprocity is fundamental to light transport and is a concept that holds also in rather complex systems. Yet, reciprocity can be switched off even in linear, isotropic, and passive media by setting the material structure into motion. In highly dispersive multilayers this leads to a fairly large forward-backward asymmetry in the pulse transmission. Moreover, in multilevel systems, this transport phenomenon can be all-optically enhanced. For atomic multilayer structures made of three-level cold 87Rb atoms, for instance, forward-backward transmission contrast around 95% can be obtained already at atomic speeds in the meter per second range. The scheme we illustrate may open up avenues for optical isolation that were not previously accessible.

All-optical routing by light storage in a Pr3+:Y2SiO5 crystal

We experimentally demonstrate an all-optical routing based on light storage in a Pr3+:Y2SiO5 crystal. Under electromagnetically induced transparency, the optical information of the probe light pulse can be stored in the crystal. By simultaneously switching on two retrieve control fields in the release process, the stored optical information from one light channel can be distributed into two light channels. Such an all-optical routing in solids may have practical applications in quantum information and all-optical network.

Simulating spontaneously generated coherence in a four-level atomic system

We study the spontaneous emission property of a four-level atomic system driven by two coherent fields. By numerical calculations in the bare state picture, we show that such interesting phenomena as extremely narrow peaks and spontaneous emission quenching can be realized, which are well understood by qualitative explanations in the partially and fully dressed state pictures. Especially, this coherently driven atomic system has two close-lying levels in the partially dressed state picture so that spontaneously generated coherence arises. Using our considered scheme it is feasible to carry out experiments based on spontaneously generated coherence because all rigorous requirements have been avoided in the bare state picture.

Erasure of stored optical information in a Pr3+:Y2SiO5 crystal

We experimentally demonstrate an erasure of stored optical information in a Pr3+:Y2SiO5 crystal by applying an erasing pulse to destroy atomic spin coherence. We observed an erasing efficiency of about 85%. Such an erasing operation of stored optical information may have practical applications in the field of information processing and all-optical network.

Coherent perfect absorption, transmission, and synthesis in a double-cavity optomechanical system

We study a double-cavity optomechanical system in which a movable mirror with perfect reflection is inserted between two fixed mirrors with partial transmission. This optomechanical system is driven from both fixed end mirrors in a symmetric scheme by two strong coupling fields and two weak probe fields. We find that three interesting phenomena: coherent perfect absorption (CPA), coherent perfect transmission (CPT), and coherent perfect synthesis (CPS) can be attained within different parameter regimes. That is, we can make two input probe fields totally absorbed by the movable mirror without yielding any energy output from either end mirror (CPA); make an input probe field transmitted from one end mirror to the other end mirror without suffering any energy loss in the two cavities (CPT); make two input probe fields synthesized into one output probe field after undergoing either a perfect transmission or a perfect reflection (CPS). These interesting phenomena originate from the efficient hybrid coupling of optical and mechanical modes and may be all-optically controlled to realize novel photonic devices in quantum information networks.

Probe gain with population inversion in a four-level atomic system with vacuum-induced coherence

For a four-level atomic system with a doublet of closely spaced levels, we find that, owing to the coherence that results from the vacuum of the radiation field, population trapping at excited levels and probe gain with population inversion can be achieved with weak incoherent pumping. This gain is different from both the conventional lasing gain and gain without inversion in that there exists population inversion on probe transitions but the inversion is achieved by the vacuum-induced coherence.

Enhanced four-wave mixing by atomic coherence in a Pr3+:Y2SiO5 crystal

We experimentally demonstrate an enhanced four-wave mixing (FWM) based on atomic coherence in a Pr3+:Y2SiO5 crystal. By employing coherent population return and fractional stimulated Raman adiabatic passage to prepare maximum atomic coherence in the crystal, an efficient FWM signal can be generated. By measuring the generated FWM signal, the time-dependent atomic coherence is monitored. Such an enhanced FWM in solids may have practical applications in nonlinear optics and laser spectroscopy.

Slowing and storage of double light pulses in a Pr3+:Y2SiO5 crystal.

We experimentally demonstrate the slowing and storage of double light pulses in a Pr(3+):Y(2)SiO(5) crystal using a multilevel-tripod scheme. Owing to double dark-state polaritons of the tripod-type system, two signal pulses can be simultaneously slowed. Also, we realize the simultaneous storage (and retrieval) of double light pulses by switching off (and back on) the control field. Slowing and storage of double light pulses in solids may have practical applications in quantum information and quantum networks.