Wei-Ping Huang’s research while affiliated with Guangdong Academy of Medical Sciences and General Hospital and other places

Neuroinflammatory deregulation in the brain plays a crucial role in the pathogenesis of sepsis associated encephalopathy (SAE). Given the mounting evidence of anti-inflammatory and neuroprotective effects of the cholinergic nervous system, it is surprising that there is little information about its changes in the brain during sepsis. To elucidate the role of the cholinergic nervous system in SAE, hippocampal choline acetyltransferase, muscarinic acetylcholine receptor-1, acetylcholinesterase and acetylcholine were evaluated in LPS-induced sepsis rats. Expression of pro-inflammatory cytokines, neuronal apoptosis, and animal cognitive performance were also assessed. Furthermore, therapeutic effects of the acetylcholinesterase inhibitor Huperzine A (HupA) on the hippocampal cholinergic nervous function and neuroinflammation were evaluated. A deficiency of the cholinergic nervous function was revealed in SAE, accompanied with over-expressed pro-inflammatory cytokines, increase in neuronal apoptosis and brain cognitive impairment. HupA remarkably promoted the deficient cholinergic nervous function and attenuated the abnormal neuroinflammation in SAE, paralleled with the recovery of brain function. We suggest that the deficiency of the cholinergic nervous function and the abnormal neuroinflammation are synergistically implicated in the pathogenesis of SAE. Thus, HupA is a potential therapeutic candidate for SAE, as it improves the deficient cholinergic nervous function and exerts anti-inflammatory action.

A low-loss surface plasmonic polariton (SPP) laser is designed as a candidate for the light-source in large-scale integrated (LSI) photonic circuits. Key design parameters of the laser are discussed and optimized to enhance the optical gain and minimize the metallic absorption loss. Performance of the laser is calculated to verify the device feasibility in the designed application.

Theoretical modeling and numerical simulation have been performed at λ = 2100 nm on silicon-on-insulator channel-waveguide directional couplers in which the outer two Si waveguides are passive and the central waveguide(s) are electro-optical (EO) “islands.” The EO channel(s) utilize a 10 nm layer of Ge 2 Sb 2 Te 5 phase-change-material sited at midlevel of a doped Si channel. A voltage-driven phase change produces a large change in the effective index of the TE o and TM o modes, thereby inducing crossbar 2 × 2 switching. A mode-matching method is employed to estimate EO switching performance in the limit of strong interguide coupling. Low-loss switching is predicted for cross-to-bar and bar-to-cross coupling lengths. These “self-holding” switches had active lengths of 500–1000 μm, which are shorter than those in couplers relying upon free-carrier injection. The four-waveguide devices had lower cross talk but higher loss than the three-waveguide devices. For the crystalline phase we sometimes used an active length that was smaller than that for the amorphous phase.

This paper reports theoretical designs and simulations of electrooptical 2 × 2 switches and 1 × 1 loss modulators based upon GST-embedded SOI channel waveguides. It is assumed that the amorphous and crystalline phases of GST can be triggered electrically by Joule heating current applied to a 10-nm GST film sandwiched between doped-Si waveguide strips. TEo and TMo mode effective indices are calculated over 1.3 to 2.1-μm wavelength range. For 2 × 2 Mach–Zehnder and directional coupler switches, low insertion loss, low crosstalk, and short device lengths are predicted for 2.1 μm, although a decreased performance is projected for 1.55 μm. For 1.3–2.1 μm, the 1 × 1 EO waveguide has application as a variable optical attenuator and as a digital modulator, albeit with ≦100-ns state-transition time. Because the active material has two “stable” phases, the device holds itself in either state, and voltage needs to be applied only during transition.

Two fundamental principles of the mode-matching method-mode orthogonality and tangential field continuity conditions have been revisited in depth. With a finite number of modes employed in the conventional method, the tangential field continuity condition at the waveguide-discontinuity interface fails leading to a field mismatch error. We propose an alternate, superior mode-matching method implemented by reconstruction of the auxiliary coefficient matrix, rather than by applying the above-mentioned continuity and orthogonality. Detailed transfer-matrix equations have been derived for the finite-mode-number case. We showed that the improved mode-matching method yields a smaller field mismatch error under equal computational effort. Examples of bent and faceted waveguide structure have been investigated and the numerical simulation results demonstrated that the newly proposed method has the merits of simple implementation, high accuracy, and high computational efficiency for application in high-index-contrast photonic integrated circuits.

New designs for electro-optical free-space and waveguided 2 x 2 switches are presented and analyzed at the 1.55 μm telecoms wavelength. The proposed devices employ a ~10 nm film of GeSe that is electrically actuated to transition the layer forth-and-back from the amorphous to the crystal phase, yielding a switch with two self-sustaining states. This phase change material was selected for its very low absorption loss at the operation wavelength, along with its electro-refraction Δn ~0.6. All switches are cascadeable into N x M devices. The free-space prism-shaped structures use III-V prism material to match the GeSe crystal index. The Si/GeSe/Si “active waveguides” are quite suitable for directional-coupler switches as well as Mach-Zehnder devices—all of which have an active length 16x less than that in the free-carrier art.

We have investigated a hybrid plasmonic-photonic mode in Si and Ge channel waveguides over the 1.55-8.0 μm wavelength range. A 10-nm Cu ribbon was buried midway within a Si3N4 “photonic slot” centered in the semiconductor strip. For the TMo mode, propagation lengths L of several millimeters are predicted for a waveguide cross-section of about 0.7λ/n x 0.7λ/n which offers optical confinement mainly within the ~λ²/400-area slot. The L increased strongly with λ. For 0.4λ/n x 0.4λ/n channels, we found multi-centimeter propagation, but there ~60% of the propagating energy had leaked out into the thick, all-around Si3N4 cladding.

Radiation coupling plays a key role in the bending waveguide structure with very small bending radius. Insights of radiation coupling and energy transfer by way of high order bending modes have been discussed. Modes in bending waveguide structures with small bending radii are investigated.

Passive optical network (PON) is considered as the most appealing access network architecture in terms of cost-effectiveness, bandwidth management flexibility, scalability and durability. And to further reduce the cost per subscriber, a Fabry-Perot (FP) laser diode is preferred as the transmitter at the optical network units (ONUs) because of its lower cost compared to distributed feedback (DFB) laser diode. However, the mode partition noise (MPN) associated with the multi-longitudinal-mode FP laser diode becomes the limiting factor in the network. This paper studies the MPN characteristics of the FP laser diode using the time-domain simulation of noise-driven multi-mode laser rate equation. The probability density functions are calculated for each longitudinal mode. The paper focuses on the investigation of the k-factor, which is a simple yet important measure of the noise power, but is usually taken as a fitted or assumed value in the penalty calculations. In this paper, the sources of the k-factor are studied with simulation, including the intrinsic source of the laser Langevin noise, and the extrinsic source of the bit pattern. The photon waveforms are shown under four simulation conditions for regular or random bit pattern, and with or without Langevin noise. The k-factors contributed by those sources are studied with a variety of bias current and modulation current. Simulation results are illustrated in figures, and show that the contribution of Langevin noise to the k-factor is larger than that of the random bit pattern, and is more dominant at lower bias current or higher modulation current.

The single-mode plasmonic Fabry–Perot (FP) lasers are designed by introducing an inversely heavily doped semiconductor layer to the Schottky contact, to provide both carrier confinement and adjustable barrier for the III–V type high gain materials. The pixel method is also used to allocate non-periodic slot positions onto the FP cavity for the single-mode filtering and selection.