Enhanced absorption and electrical modulation of graphene based on the parity-time symmetry optical structure

In order to realize the ultrastrong absorption of graphene with electrical modulation properties, we designed a composite structure of graphene and parity-time(PT) symmetry photonic crystal, which is achieved by placing the graphene layer on the top layer of the PT symmetry photonic crystal. In this paper, the absorption properties of graphene and the electrical modulating properties of the structure were theoretically analyzed based on the transfer matrix method. The result shows that the proposed structure can achieve the absorption of 31.5 d B for the communication wavelength of 1550 nm;meanwhile,by setting the electric field intensity to ±0.02 V/nm, the absorption of graphene can be largely modulated to realize an electrically switchable effect, the modulation depth of graphene absorption can reach nearly 100%, and the operation speed is also close to 8.171 GHz. This investigation provides a novel approach to design graphene-based optoelectronic devices and optical communication devices.

Photo-Doped Active Electrically Controlled Terahertz Modulator

We demonstrate an electric-controlled terahertz（THz） modulator which can be used to realize amplitude modulation of terahertz waves with slight photo-doping. The THz pulse transmission was efficiently modulated by electrically controlling the monolayer silicon-based device. The modulation depth reached 100% almost when the applied voltage was 7V at an external laser intensity of 0.6W/cm2. The saturation voltage reduced with the increase of the photo-excited intensity. In a THz continuous wave（CW）system, a significant fall in both THz transmission and reflection was also observed with the increase of applied voltage. This reduction in the THz transmission and reflection was induced by the absorption for electron injection. The results show that a high-efficiency and high modulation depth broadband electric-controlled terahertz modulator in a pure Si structure has been realized.

Stimulation strategies for electrical and magnetic modulation of cells and tissues

Electrical phenomena play an important role in numerous biological processes including cellular signaling,early embryogenesis,tissue repair and remodeling,and growth of organisms.Electrical and magnetic effects have been studied on a variety of stimulation strategies and cell types regarding cellular functions and disease treatments.In this review,we discuss recent advances in using three different stimulation strategies,namely electrical stimulation via conductive and piezoelectric materials as well as magnetic stimulation via magnetic materials,to modulate cell and tissue properties.These three strategies offer distinct stimulation routes given specific material characteristics.This review will evaluate material properties and biological response for these stimulation strategies with respect to their potential applications in neural and musculoskeletal research.

Electrical control of excitonic oscillator strength and spatial distribution in a monolayer semiconductor

Electrical modulation of luminescence is significant to modern light-emitting devices.Monolayer transition metal dichalcogenides are emerging direct-bandgap luminescent materials with unique excitonic properties,and the multiple exciton complexes provide new opportunities to modulate the property of luminescence in atomically thin semiconductors.Here,we report an electrical control of exciton emission in the oscillator strength and spatial distribution of excitons in a monolayer WS2.Effective modulation of excitonic emission intensity with a degree of modulation of~92%has been demonstrated by an electric field at room temperature.The spatial carrier redistribution tuned by a lateral electric field results in distinct excitonic emission patterns by design.The modulation approach to exciton oscillator strength and distribution provides an efficient way to investigate the exciton diffusion dynamics and to construct electrically tunable optoelectronic devices.

Electrically tunable optical metasurfaces

Optical metasurfaces have emerged as a groundbreaking technology in photonics,offering unparalleled control over light-matter interactions at the subwavelength scale with ultrathin surface nanostructures and thereby giving birth to flat optics.While most reported optical metasurfaces are static,featuring well-defined optical responses determined by their compositions and configurations set during fabrication,dynamic optical metasurfaces with reconfigurable functionalities by applying thermal,electrical,or optical stimuli have become increasingly more in demand and moved to the forefront of research and development.Among various types of dynamically controlled metasurfaces,electrically tunable optical metasurfaces have shown great promise due to their fast response time,low power consumption,and compatibility with existing electronic control systems,offering unique possibilities for dynamic tunability of light–matter interactions via electrical modulation.Here we provide a comprehensive overview of the state-of-the-art design methodologies and technologies explored in this rapidly evolving field.Our work delves into the fundamental principles of electrical modulation,various materials and mechanisms enabling tunability,and representative applications for active light-field manipulation,including optical amplitude and phase modulators,tunable polarization optics and wavelength filters,and dynamic waveshaping optics,including holograms and displays.The review terminates with our perspectives on the future development of electrically triggered optical metasurfaces.

High-voltage super-junction lateral double-diffused metal-oxide semiconductor with a partial lightly doped pillar

A novel super-junction lateral double-diffused metal-oxide semiconductor （SJ-LDMOS） with a partial lightly doped P pillar （PD） is proposed. Firstly, the reduction in the partial P pillar charges ensures the charge balance and suppresses the substrate-assisted depletion effect. Secondly, the new electric field peak produced by the P/P junction modulates the surface electric field distribution. Both of these result in a high breakdown voltage （BV）. In addition, due to the same conduction paths, the specific on-resistance （Ron,sp） of the PD SJ-LDMOS is approximately identical to the conventional SJ-LDMOS. Simulation results indicate that the average value of the surface lateral electric field of the PD SJ-LDMOS reaches 20 V/μm at a 15 μm drift length, resulting in a BV of 300 V.

Novel fast-switching LIGBT with P-buried layer and partial SOI

A novel silicon-on-insulator lateral insulated gate bipolar transistor(SOI LIGBT)is proposed in this paper.The proposed device has a P-type buried layer and a partial-SOI layer,which is called the BPSOI-LIGBT.Due to the electric field modulation effect generated by the P-type buried layer and the partial-SOI layer,the proposed structure generates two new peaks in the surface electric field distribution,which can achieve a smaller device size with a higher breakdown voltage.The smaller size of the device is beneficial to the fast switching.The simulation shows that under the same size,the breakdown voltage of the BPSOI LIGBT is 26%higher than that of the conventional partial-SOI LIGBT(PSOI LIGBT),and 84%higher than the traditional SOI LIGBT.When the forward voltage drop is 2.05 V,the turn-off time of the BPSOI LIGBT is 71%shorter than that of the traditional SOI LIGBT.Therefore,the proposed BPSOI LIGBT has a better forward voltage drop and turn-off time trade-off than the traditional SOI LIGBT.In addition,the BPSOI LIGBT effectively relieves the self-heating effect of the traditional SOI LIGBT.

Breakdown voltage analysis of Al_(0.25)Ga_(0.75)N/GaN high electron mobility transistors with partial silicon doping in the AlGaN layer

In this paper,two-dimensional electron gas（2DEG） regions in AlGaN/GaN high electron mobility transistors（HEMTs） are realized by doping partial silicon into the AlGaN layer for the first time.A new electric field peak is introduced along the interface between the AlGaN and GaN buffer by the electric field modulation effect due to partial silicon positive charge.The high electric field near the gate for the complete silicon doping structure is effectively decreased,which makes the surface electric field uniform.The high electric field peak near the drain results from the potential difference between the surface and the depletion regions.Simulated breakdown curves that are the same as the test results are obtained for the first time by introducing an acceptor-like trap into the N-type GaN buffer.The proposed structure with partial silicon doping is better than the structure with complete silicon doping and conventional structures with the electric field plate near the drain.The breakdown voltage is improved from 296 V for the conventional structure to 400 V for the proposed one resulting from the uniform surface electric field.

Low on-resistance high-voltage lateral double-diffused metal oxide semiconductor with a buried improved super-junction layer

A novel low specific on-resistance （Ron,sp） lateral double-diffused metal oxide semiconductor （LDMOS） with a buried improved super-junction （BISJ） layer is proposed. A super-junction layer is buried in the drift region and the P pillar is split into two parts with different doping concentrations. Firstly, the buried super-junction layer causes the multiple-direction assisted depletion effect. The drift region doping concentration of the BISJ LDMOS is therefore much higher than that of the conventional LDMOS. Secondly, the buried super-junction layer provides a bulk low on-resistance path. Both of them reduce Ron,sp greatly. Thirdly, the electric field modulation effect of the new electric field peak introduced by the step doped P pillar improves the breakdown voltage （BV）. The BISJ LDMOS exhibits a BV of 300 V and Ron,sp of 8.08 mΩ·cm2 which increases BV by 35% and reduces Ron,sp by 60% compared with those of a conventional LDMOS with a drift length of 15 μm, respectively.

Fast-switching SOI-LIGBT with compound dielectric buried layer and assistant-depletion trench

A lateral insulated gate bipolar transistor(LIGBT)based on silicon-on-insulator(SOI)structure is proposed and investigated.This device features a compound dielectric buried layer(CDBL)and an assistant-depletion trench(ADT).The CDBL is employed to introduce two high electric field peaks that optimize the electric field distributions and that,under the same breakdown voltage(BV)condition,allow the CDBL to acquire a drift region of shorter length and a smaller number of stored carriers.Reducing their numbers helps in fast-switching.Furthermore,the ADT contributes to the rapid extraction of the stored carriers from the drift region as well as the formation of an additional heat-flow channel.The simulation results show that the BV of the proposed LIGBT is increased by 113%compared with the conventional SOI LIGBT of the same length L_(D).Contrastingly,the length of the drift region of the proposed device(11.2μm)is about one third that of a traditional device(33μm)with the same BV of 141 V.Therefore,the turn-off loss(E_(OFF))of the CDBL SOI LIGBT is decreased by 88.7%compared with a conventional SOI LIGBT when the forward voltage drop(VF)is 1.64 V.Moreover,the short-circuit failure time of the proposed device is 45%longer than that of the conventional SOI LIGBT.Therefor,the proposed CDBL SOI LIGBT exhibits a better V_(F)-E_(OFF)tradeoff and an improved short-circuit robustness.

Sensorless Control on a Dual-Fed Flux Modulated Electric Motor

This paper proposes the operation principle and a new flux estimation method for sensorless control strategy for the dual-fed flux modulated electric motor(DFFM).The DFFM is designed based on the flux modulation theory,it includes two stator windings and one rotor which simplify the mechanical structure.The rotor has only modulation iron and no permanent magnets on it,so there is no cogging torque problem in this motor.With adjustment of the outer and inner stator flux rotating frequency and amplitude,different rotation speed and torque of the sandwiched rotor can be gained for the DFFM.Furthermore,an improved flux estimation based sensorless control strategy is performed on the proposed machine to fit the two winding set control situation.The startup and performance of the proposed control strategy is verified by the simulation and experiments.

Flow control characteristics of the digital and mechanical redundancy control electric modulation valve

The electrical modulation valve can provide proportional output valve element displacement,flow,or pressure according to a continuously changing input electrical signal.It is the core component of electro-hydraulic proportional control technology.To remove the influence of pressure difference changes on the output flow,the traditional scheme is to use a pressure compensation valve,which increases the difficulty of both manufacturing and maintaining the valve.To solve this problem,a method of digital and mechanical redundancy control flow is proposed.Pressure sensors are installed at the inlet and outlet of the valve,and the controller adjusts the displacement of the valve element according to the pressure difference between the valve ports to realize high-precision control of the flow.A pressure compensation valve is installed in front of the valve,and a three-way solenoid valve is used to control the working of the compensation valve.In the case of sensor failure,the valve is switched to the mechanical compensation differential pressure mode,to control the flow and to achieve redundancy control.The system security is thereby improved.The feasibility of this scheme is verified through simulation and tests.The results show that,both for digital compensation and mechanical compensation,the output flow can be kept constant when the pressure difference changes,and the system has good static and dynamic characteristics.The principle can be applied to the displacement-flow feedback type electrical modulation valve,and can realize accurate control of the flow of the pilot valve and,finally,accurate control of the flow in the main valve.

Effect of tilt angle on the performance and electrical parameters of a PV module:Comparative indoor and outdoor experimental investigation

Photovoltaic(PV)system’s performance is significantly affected by its orientation and tilt angle.Experimental investigation(indoor and outdoor)has been carried out to trace the variation in PV performance and electrical parameters at varying tilt angles in Malaysian conditions.There were two experimental modus:1)varying module tilt under constant irradiation level,2)varying irradiation intensity at the optimum tilt set up.For the former scheme,the irradiation level was maintained at 750 W/m^(2),and for the later arrangement,the module tilt angle was varied from 0 o to 80 o by means of a single-axis tracker.Results show that under constant irradiation of 750 W/m^(2),every 5 o increase in tilt angle causes a power drop of 2.09 W at indoor and 3.45 W at outdoor.In contrast,for the same condition,efficiency decreases by 0.54%for indoor case and by 0.76%at outdoor.On the other hand,for every 100 W/m^(2)increase in irradiation,solar cell temperature rises by 7.52℃at indoor and by 5.67℃at outdoor.As of module electrical parameters,open-circuit voltage,short-circuit current,maximum power point voltage and maximum power point current drops substantially with increasing tilt angle,whereas fill factor drops rather gradually.Outdoor experimental investigation confirms that the optimum tilt angle at Malaysian conditions is 15 o and orienting a PV module this angle will maximize the sun’s energy captured and thereby enhance its performance.

Electrical nonlinearity in silicon modulators based on reversed PN junctions

The electrical nonlinearity of silicon modulators based on reversed PN junctions was found to severely limit the linearity of the modulators.This effect,however,was inadvertently neglected in previous studies.Considering the electrical nonlinearity in simulation,a 32.2 dB degradation in the CDR3(i.e.,the suppression ratio between the fundamental signal and intermodulation distortion)of the modulator was observed at a modulation speed of 12 GHz,and the spurious free dynamic range was simultaneously degraded by 17.4 dB.It was also found that the linearity of the silicon modulator could be improved by reducing the series resistance of the PN junction.The frequency dependence of the linearity due to the electrical nonlinearity was also investigated.

Numerical Analysis of Electrically Tunable Delay-Line with an SSB Modulator

By using an optical system simulator, we investigated the tunable delay-line with an optical SSB modulator and an optical fiber loop, where the delay can be controlled by the electric signal fed to the modulator.

Influence of dynamic power dissipation on Si MRM modulation characteristics

We experimentally observe that Si micro-ring modulator（MRM） modulation characteristics are strongly influenced by the modulation data rate and the data pattern and determine this influence is due to the temperature increase caused by dynamic power dissipation within the Si MRM device. We also quantitatively determine the amount of Si MRM resonance wavelength shift due to different modulation data rates, data patterns, and modulation voltages. Our results should be of great help for achieving reliable and optimal modulation characteristics for Si MRMs.

A high voltage Bi-CMOS compatible buffer super-junction LDMOS with an N-type buried layer

A novel buffer super-junction （S J） lateral double-diffused MOSFET （LDMOS） with an N-type buried layer （NB） is proposed. An N- buffer layer is implemented under the SJ region and an N-type layer is buried in the P substrate. Firstly, the new electric field peak introduced by the p-n junction of the P substrate and the N-type buried layer modulates the surface electric field distribution. Secondly, the N-buffer layer suppresses the substrate assisted depletion effect. Both of them improve the breakdown voltage （BV）. Finally, because of the shallow depth of the SJ region, the NB buffer SJ-LDMOS is compatible with Bi-CMOS technology. Simulation results indicate that the average value of the surface lateral electric field strength of the NB buffer SJ-LDMOS reaches 23 V/μm at 15/μm drift length which results in a BV of 350 V and a specific on-resistance of 21 mΩ·cm2.

Novel 700 V high-voltage SOI LDMOS structure with folded drift region

A new high-voltage LDMOS with folded drift region （FDR LDMOS） is proposed. The drift region is folded by introducing the interdigital oxide layer in the： Si active layer, the result of which is that the effective length of the drift region is increased significantly. The breakdown characteristic has been improved by the shielding effect of the electric field from the holes accumulated in the surface of the device and the buried oxide layer. The numerical results indicate that the breakdown voltage of 700 V is obtained in the proposed device in comparison to 300 V of conventional LDMOS, while maintaining low on-resistance.