量子棒中强耦合氢化杂质束缚磁极化子基态性质的磁场和温度依赖性

Magnetic field and temperature dependence of the properties of the ground state of the strong-coupling bound magnetopolaron in quantum rods(QRs) with hydrogenic impurity is studied by means of the Huybrechts-Lee -Low-Pines transformation method and the quantum statistical theory.The expressions for the ground-state energy and the mean number of phonons of the magnetopolaron are derived.Results of the numerical calculations show that the bound state of the magnetopolaron cannot be formed when the value of the aspect ratio of the QR,the dielectric constant ratio,the electron-phonon coupling strength or the temperature parameter is small.The larger the deviation of the value of aspect ratio e’from 1 is,the more it is unfavorable to the stability of the ground state of the magnetopolaron.When the magnetopolaron is in the bound state,the absolute value of its ground-state energy and its mean number of phonons increase with an increase of the dielectric constant ratio and confinement strength of QRs,but decrease with an increase in the cyclotron frequency of the external magnetic field and the temperature. The absolute value of the ground-state energy and the mean number of phonons of the magnetopolaron decrease with decreasing e’when e’<1,but decrease with increasing e’when e’>1.They get the maximum value at e’=1.     

Influence of relative phase on propagation effect in open V-type three-level system

In this paper we study the influence of the relative phase between the probe and driving fields on propagation effect in an open Doppler broadening V-type three-level atomic system with spontaneously generated coherence(SGC) by using the calculation result of the density matrix motion equations and the propagation equations of the driving and probe fields.It is shown that the relative phase(Φ) has remarkable periodical influence on the propagation effect,and the period is 2π.By selecting appropriate value of Φ,we can get larger lasing without in version(LWI) gain and longer propagation distance in which gain exists,and hence obtain higher probe field(i.e.LWI) intensity.When Φ=π/2,the largest LWI gain and probe field intensity can be got.In addition,the atomic exit rate(γ0) and ratio(S) of the atomic injection rates also have a considerable modulation role on the phase-dependent propagation effect.In certain value range of γ0(S),LWI gain and probe field intensity increase with γ0(S) increasing.In the open system,LWI gain and probe field intensity much larger than those in the corresponding closed system can be obtained.     

Effect of exit and injection rates on phase-dependent transient evolution of gain without inversion

It is shown that in an open Λ-type system with spontaneously generated coherence, the transient evolution rule of the gain of lasing without inversion (LWI) is very sensitive to variation of the relative phase φ between the probe and driving fields; the variety of the atomic exit rateγ_0 and the ratio C of the atomic injection rates also have a considerable effect on the phase-dependent transient evolution rule of LWI gain. We find that whenφ=0, the transient and stationary LWI gain increases with C increasing but decreases with γ_0 increasing; whenφ≠0 , the effect of C andγ_0 on LWI gain is just opposite to that when φ=0 ; in order to get the largest transient and stationary LWI gain, we need selecting suitable values of φ,γ_0 and C.     

Effect on the Propagation Characteristics of the Electromagnetic Waves by the Second-order Radiation of the Moving High-speed Train＊

The effect on the propagation characteris- tics of the electromagnetic waves by the second-order ra- diation of the moving high-speed train is analyzed in this paper. Two Lorentz transformations, one from the sta- tionary reference coordinate system to the moving system and the other vice versa, are employed to derive the the- oretical model for analysis of the propagation characteris- tics of the vertical polarized plane time-harmonic waves, which is oblique incidence to the train. The calculation re- suits show that for the transmitting wave reflected by the moving high-speed train, two main signals can be received. One is at the transmitting frequency and the other is at the second-order radiated frequency. The frequency spectrum between these two frequencies are much larger than which is introduced by the Doppler shift. The frequency and the reflection angle of the reflected wave are no longer equal to the frequency and the incident angle of the incident wave. The changed reflection frequency and angle are related to the train＇s velocity, the incident angle and the azimuth an- gle of the incident wave. The frequency shift is mainly decided by the y-component of the train＇s velocity. It has nothing to do with y-component of the train＇s velocity. The reflection angles will be smaller than the related incident angles when the train goes along --y direction. The reflec- tion angles will be larger than the related incident angles when the train goes along ＋y direction. The reflection an- gle will become larger and larger with the increase of the incident angle and the y-component of the train＇s velocity. The induced current density and the charge density on the surface of the train are increased with the train＇s velocity, and the induced charge is much smaller than the induced current.     

Numerical simulation of asymmetric dual-core fiber with large group-velocity dispersion

The asymmetric dual-core fiber(ADCF) is proposed to obtain large group velocity dispersion(GVD) because of the coupling effects between the fundamental modes of the central core and high-order modes of the side core. The supermodes of the ADCF can provide anomalous-and normal-GVD profiles with large peak values at the maximum dispersion wavelengths. The maximum dispersion wavelengths can be shifted in the wavelength window of 1 550 nm by properly tuning the refractive indexes and diameters of the cores or spacing between the two cores. Furthermore, the numerical results show that the ADCF with the normal-GVD supermode 1 can be employed in the pulse broadening, where the broadening factor can reach more than 30 without pulse distortion from nonlinear effects.     

Effects of hydrostatic pressure and external electric field on the impurity binding energy in strained GaN/AlxGa1?xN spherical quantum dots

The binding energy and Stark effect energy shifts of a shallow donor impurity state in a strained GaN/AlxGa1-xN spherical finite-potential quantum dot (QD) are calculated using a variational method based on the effective mass approximation. The binding energy is computed as a function of dot size and hydrostatic pressure. The numerical results show that the binding energy of the impurity state increases, attains a maximum value, and then decreases as the QD radius increases for any electric field. Moreover, the binding energy increases with the pressure for any size of dot. The Stark shift of the impurity energy for large dot size is much larger than that for the small dot size, and it is enhanced by the increase of electric field. We compare the binding energy of impurity state with and without strain effects, and the results show that the strain effects enhance the impurity binding energy considerably, especially for the small QD size. We also take the dielectric mismatch into account in our work.     

Magnetic field and temperature dependence of the groundstate energy of weak-coupling magnetopolaron in quantum rods with hydrogenic impurity

The dependence of the ground-state properties of weak-coupling bound magnetopolarons in quantum rods (QRs) with hydrogenic impurity on magnetic field and temperature is studied by means of the Lee-Low-Pines (LLP) transformation method and Huybrechts linear combination operator method. The expression for the ground-state energy of the magnetopolaron is derived. Results of the numerical calculations show that the ground-state energy of weak-coupling bound magnetopolarons in QRs with hydrogenic impurity increases with increasing the cyclotron frequency of the magnetic field, the confinement strength of QRs and the temperature, but decreases with increasing the electron-phonon coupling strength and the dielectric constant ratio. The stability of the ground state of magnetopolarons is closely related to the aspect ratio e′of the QR. The ground state of magnetopolarons is the most stable at e′=1. The stability of the ground state of magnetopolarons can remarkably decrease when the value of the aspect ratio increases or decreases from 1.     

Simulation of electrical properties of InxAl1-xN/AlN/GaN high electron mobility transistor structure

Electrical properties of In_x Al_1-xN/AlN/GaN structure are investigated by solving coupled Schr（o|¨）dinger and Poisson equations self-consistently.The variations in internal polarizations in In_xAl_1-xN with indium contents are studied and the total polarization is zero when the indium content is 0.41.Our calculations show that the twodimensional electron gas（2DEG） sheet density will decrease with increasing indium content.There is a critical thickness for AIN.The 2DEG sheet density will increase with In_xAl_1-xN thickness when the AIN thickness is less than the critical value.However,once the AIN thickness becomes greater than the critical value,the 2DEG sheet density will decrease with increasing barrier thickness.The critical value of AIN is 2.8 nm for the lattice-matched In_0.18Al_0.82N/AlN/GaN structure.Our calculations also show that the critical value decreases with increasing indium content.     

Evolution of Electron Phase Orbits of Multi-photon Nonlinear Compton Scattering in High Power Laser-plasma

The evolution of the electron phase orbits based on the multi-photon nonlinear Compton scattering with the high power laser-plasma is discussed by using Kroll-Morton-Rosenbluth theory. The random evolution of the un-captured electron phase orbits from periodicity to non-periodicity is found after the energy has been exchanged between the electron and photons. With the increase of the absorbed photon number n by an electron,this evolution will be more and more intense, while which is rapidly decreased with the enhancement of the collision non-flexibility ξ and their initial speeds of the electrons and photons, but this evolution is lower than that in the high power laser field. When the electrons are captured by the laser field, the evolution is finished, and the electrons will stably transport, and the photons don‘t provide the energy for these electrons any more.     

Nano inhomogeneity effects on small Ag/n-Si Schottky diode parameters at high temperature

Schottky diodes with an Ag/n-Si/W/Cu structure and 100μm in diameter were studied.Analyzing the silver metal surface coating on the n-Si substrate using a scanning probe microscopy(SPM) device showed a large number of nano patches in the surface with dimensions of 0 to 100 nm.The potential distribution of the patches revealed that the potential of each patch with the neighboring patches was different.The electrical characteristics of the devices were studied between temperature ranges of 300 and 380 K.When the temperature ideality factor approximately increases,the potential barrier height decreases.The potential barrier height was calculated separately from theⅠ-Ⅴand C-V characteristics.The main reasons for the significant difference between room temperature and higher temperatures were the differences in patch distribution,the different potentials of each patch,and the interactions between them.The effective potential barrier height depended on the degree of inhomogeneity,and thus the operating potential barrier height in the contact surface was smaller than the average value,and the ideality factor was more than unitary.With the increase in the potential value,the ideality factor becomes close to unitary, and with increasing temperatures,the ideality factor is increased.In this case,the maximum potential barrier height accrues at a greater distance from the metal contact.For this reason,at high temperatures the average value of the potential barrier height is smaller.Moreover,with increasing temperature,the ideality factor is increased.     

基于GaAs基大功率激光器的热分析

The thermal characteristics of 808 nm Al Ga As/Ga As laser diodes(LDs) are analyzed via electrical transient measurements and infrared thermography. The temperature rise and thermal resistance are measured at various input currents and powers. From the electrical transient measurements, it is found that there is a significant reduction in thermal resistance with increasing power because of the device power conversion efficiency. The component thermal resistance that was obtained from the structure function showed that the total thermal resistance is mainly composed of the thermal resistance of the sub-mount rather than that of the LD chip, and the thermal resistance of the sub-mount decreases with increasing current. The temperature rise values are also measured by infrared thermography and are calibrated based on a reference image, with results that are lower than those determined by electrical transient measurements. The difference in the results is caused by the limited spatial resolution of the measurements and by the signal being captured from the facet rather than from the junction of the laser diode.     

Effects of negative index medium defect layers on the transmission properties of one-dimensional photonic crystal

The photonic band gap structure of 1D photonic crystal with a negative index medium defect layer is studied by using the transfer matrix method. Investigations show that the introdution of negative index medium defect layer and the increase of the negative index value will result in an extension of the band gap. Moreover, by increasing the negative index, the width of defect layer and the numbers of period photonic crystal, the width of defect modes will be narrowed, which is advantaged to obtain optical filters with narrow band. Finally, the effects of absorption on the properties of band gap and on defect modes have been discussed.     

A non-contact real-time measurement of lamp dimension based on machine vision

The scintillation indices(SIs)of Gaussian beams and vortex beams propagating in turbulent atmosphere are investigated experimentally.It is shown that with the increase of propagation distance,the SI of Gaussian beam around optical axis increases gradually,but the SI of vortex beam with topological charge of 4 increases,achieves the maximum value at a fixed distance,and then decreases as the continued increase of propagation distance.The SI of vortex beam can be smaller than that of Gaussian beam under certain conditions.     

Attenuation of terahertz transmission through rain

Based on the Marshall-Palmer,Weibull raindrop size distribution and Mie electromagnetic scattering model,the relationships of attenuation coefficient of terahertz(THz) atmospheric window waves with precipitation rate and temperature are studied.Furthermore,combined with the loss of electromagnetic wave transmission in free space,the attenuation of THz communication and the transmission of current mobile communication signals through rain are compared and analyzed.The results show that the attenuation coefficient of THz transmission is increased with increasing precipitation rate,the difference of attenuation coefficient at different THz window waves is small,and the maximum difference is about 3 dB.The rain attenuation of THz wave is first decreased and then increased with increasing temperature,but the temperature has little effect on it.The attenuation of THz wave through rain is much larger than that of mobile communication signal.     

Drive current of accumulation-mode p-channel SOI-based wrap-gated Fin-FETs

Comparisons are performed to study the drive current of accumulation-mode(AM) p-channel wrap-gated Fin-FETs.The drive current of the AM p-channel FET is 15%-26%larger than that of the inversion-mode (IM) p-channel FET with the same wrap-gated fin channel,because of the body current component in the AM FET, which becomes less dominative as the gate overdrive becomes larger.The drive currents of the AM p-channel wrap-gated Fin-FETs are 50%larger than those of the AM p-channel planar FETs,which arises from effective conducting surface broadening and volume accumulation in the AM wrap-gated Fin-FETs.The effective conducting surface broadening is due to wrap-gate-induced multi-surface conduction,while the volume accumulation,namely the majority carrier concentration anywhere in the fin cross section exceeding the fin doping density,is due to the coupling of electric fields from different parts of the wrap gate.Moreover,for AM p-channel wrap-gated Fin-FETs, the current in channel along <110> is larger than that in channel along <100>,which arises from the surface mobility difference due to different transport directions and surface orientations.That is more obvious as the gate overdrive becomes larger,when the surface current component plays a more dominative role in the total current.     

Preparation of n-type semiconductor SnO2 thin films

We studied fluorine-doped tin oxide on a glass substrate at 350℃using an ultrasonic spray technique. Tin（Ⅱ） chloride dehydrate,ammonium fluoride dehydrate,ethanol and NaOH were used as the starting material, dopant source,solvent and stabilizer,respectively.The SnO₂:F thin films were deposited at 350℃and a pending time of 60 and 90 s.The as-grown films exhibit a hexagonal wurtzite structure and have（101） orientation.The G = 31.82 nm value of the grain size is attained from SnO₂:F film grown at 90 s,and the transmittance is greater than 80%in the visible region.The optical gap energy is found to measure 4.05 eV for the film prepared at 90 s, and the increase in the electrical conductivity of the film with the temperature of the sample is up to a maximum value of 265.58（Ω·cm）^-1,with the maximum activation energy value of the films being found to measure 22.85 meV,indicating that the films exhibit an n-type semiconducting nature.     

ANALYSIS OF INTERNALLY GENERATED NOISE OF BIOELECTRIC AMPLIFIERS

This papenr deals with internally generated noise of bioelectric amplifiers that are usually used for processing of bioelectric events.The main purpose of this paper is to present a procedure for analysis of the effects of internal noise generated by the active circuits and to evaluate the output noise of the author‘s new designed bioelectric amplifier that caused by internal effects to the amplifier circuit itself in order to compare it with the noise generated by conventional amplifiers.The obtained analysis results of internally generated noise showed that the total output noise of bioelectric active circuits does not increase when some of their resitors have a larger value.This behavior is caused by the different transfer functions for the signal and the respective noise sources associated with these resistors.Moreover,the new designed bioelectric amplifier haws an output noise less than that for conventional amplifiers.The obtained analysis results were also experimentally verified and the final conclusions were drawn.     

应变纤锌矿ZnO/MgxZn1-xO量子点中离子施主束缚激子的光学性质

Within the framework of the effective-mass approximation and the dipole approximation, considering the three-dimensional confinement of the electron and hole and the strong built-in electric field(BEF) in strained wurtzite Zn O/Mg0:25Zn0:75O quantum dots(QDs), the optical properties of ionized donor-bound excitons(D+, X)are investigated theoretically using a variational method. The computations are performed in the case of finite band offset. Numerical results indicate that the optical properties of(D+, X) complexes sensitively depend on the donor position, the QD size and the BEF. The binding energy of(D+, X) complexes is larger when the donor is located in the vicinity of the left interface of the QDs, and it decreases with increasing QD size. The oscillator strength reduces with an increase in the dot height and increases with an increase in the dot radius. Furthermore, when the QD size decreases, the absorption peak intensity shows a marked increment, and the absorption coefficient peak has a blueshift. The strong BEF causes a redshift of the absorption coefficient peak and causes the absorption peak intensity to decrease remarkably. The physical reasons for these relationships have been analyzed in depth.     

Design and Performance of an AIGaN-Based p-i-n Ultraviolet Photodetector

An AIGaN-based back-illuminated ultraviolet p-i-n detector is designed and its performance is analysed both simulately and experimentally. The width of p- and i-regions has been optimized to the best theoretic values. It is indicated that the changing of responsivity with increase of bias can not be attributed to the expansion of depletion layer as it is believed, but to two reasons： 1） the effect of GaN/AlGaN heterojunction barrier to block the electrons decreases with higher bias and 2） the recombination rate of excess carriers decreases due to the building up of an electric field in depletion region. At zero bias, the simulated responsivity reaches its maximum of 0.12 A/W with quantum efficiency of 55.1%. The measured peak responsivity is more than 0.09 A/W with quantum efficiency greater than 41.6%. The experimental data are almost consistent with the results of the simulation.     

Structural, morphological, dielectrical and magnetic properties of Mn substituted cobalt ferrite

The Co1 xMnxFe2O4(06x60.5) ferrite system is synthesized by using an auto combustion technique using metal nitrates. The influence of Mn substitution on the structural, electrical, impedance and magnetic properties of cobalt ferrite is reported. X-ray diffraction patterns of the prepared samples confirm that the Bragg’s peak belongs to a spinel cubic crystal structure. The lattice constant of cobalt ferrite increases with the increase in Mn content. The microstructural study is carried out by using the SEM technique and the average grain size continues to increase with increasing manganese content. AC conductivity analysis suggests that the conduction is due to small polaron hopping. DC electrical resistivity decreases with increasing temperature for a Co1 xMnxFe2O4system showing semiconducting behavior. The activation energy is found to be higher in the paramagnetic region than the ferromagnetic region. Curie temperature decreases with Mn substitution in the host ferrite system. Dielectric dispersionhavingMaxwell-Wagner-typeinterfacialpolarizationhasbeenobservedforcobaltferritesamples.Magnetic properties have been studied by measuring M-H plots. The saturation and remanent magnetization increases with Mn substitution.