Size measurement of nano-particles using self-mixing effect

In this letter, the technique of laser self-mixing effect is employed for nano-particle size analysis. In contrast to the photon correlation spectroscopy （PCS） and photon cross correlation spectroscopy （PCCS）, the main advantages of this technique are sensitive, compact, low-cost, and simple experimental setup etc. An improved Kaczmarz projection method is developed in the inversion problem to extract the particle size distribution. The experimental results prove that nano-particle size can be measured reasonably by using the self-mixing effect technique combined with the improved projection algorithm.     

Heralded linear optical quantum Fredkin gate based on one auxiliary qubit and one single photon detector

Linear optical quantum Fredkin gate can be applied to quantum computing and quantum multi-user communication networks. In the existing linear optical scheme, two single photon detectors （SPDs） are used to herald the success of the quantum Fredkin gate while they have no photon count. But analysis results show that for non-perfect SPD, the lower the detector efficiency, the higher the heralded success rate by this scheme is. We propose an improved linear optical quantum Fredkin gate by designing a new heralding scheme with an auxiliary qubit and only one SPD, in which the higher the detection efficiency of the heralding detector, the higher the success rate of the gate is. The new heralding scheme can also work efficiently under a non-ideal single photon source. Based on this quantum Fredkin gate, large-scale quantum switching networks can be built. As an example, a quantum Bene~ network is shown in which only one SPD is used.     

Engineering of Two Quantum States via Conditional Measurement on Two-Mode Squeezed State

We propose a scheme for the simultaneously preparation radiation-field modes of a single photon and a superposition of zero- and one-photon states, based on the coherent quantum state displacement and photon subtraction from two-mode squeezed state. It is shown that the single-photon and the superposition states can be obtained by only choosing the suitable parameter of displacements. The experimental feasibility to accomplish this scheme is also discussed.     

Effects of Raw Material Content on Efficiency of TiN Synthesized by Reactive Ball Milling Ti and Urea

Ti and urea mixed according to the molar ratios of 2：1, 3：1 and 4：1 axe milled under the same condition. The structures of the as-synthesized powders are analyzed by an x-ray diffractometer （XRD）. The decomposed temperature of the urea and the products decomposed are characterized by differential scanning calorimetry （DSC） and thermogravimetry analysis-Fourier transform infrared （TG-FTIR） spectrometry. The results show that the reaction progress is a diffusion reaction. The efficiency of TiN synthesized by reactive ball milling can be increased by increasing the content of Ti. The reactive ball milling time decreases from more than 90 h to 40 h correspond- ing to the content ratio between Ti and urea increasing from 2：1 to 4：1. Ammonia gas （NH3） and cyanic acid （HNCO）, the decomposed products of urea, react with the refined Ti to form TiN. The grain refinement of Ti has a significant effect on the efficiency of reactive ball milling.     

Lithium atom population transfer by population trapping in a chirped microwave pulse

Using a time-dependent multilevel approach, we demonstrate that lithium atoms can be transferred to states of lower principle quantum number by exposing them to a frequency chirped microwave pulse. The population transfer from n = 79 to n = 70 states of lithium atoms with more than 80% efficiency is achieved by means of the sequential two-photon Δ n = - 1 transitions. It is shown that the coherent control of the population transfer can be accomplished by the optimization of the chirping parameters and microwave field strength. The calculation results agree well with the experimental ones and novel explanations have been given to understand the experimental results.     

Zero-Chirp Return-to-Zero Pulses Generation with Two Single-Driver z-Cut Mach-Zehnder Modulators

A novel method is proposed to suppress the frequency chirp of single-driver z-cut Mach Zehnder modulators. Theoretical analysis shows that by multiplying the output pulses of a half clock frequency driving single-driver z-cut modulator with the one delayed odd multiple bit duration, the frequency chirp can be removed entirely, and return-to-zero （RZ） pulses with duty cycles of about 25% and 56% are obtained. An experimental scheme is proposed to validate the proposed method. The pulses can be obtained by using this scheme. experimental results show that perfect 40 GHz zero-chirp RZ     

用PCA方法模拟光子鉴别

The shower shape of n, n^-, p, p^-, K^＋, π^＋ and photons, generated by JPCIAE code for 5.5 TeV/A ^208pb＋^208pb collisions, incident on the ALICE photon spectrometer （PHOS）, is analyzed with the principal component analysis （PCA） method. The efficiency dependence of purity for the photon discrimination is simulated for the deposited energy ranges 0.5-2 GeV, 2-10 GeV, 10-50 GeV and 50-100 GeV. The result shows that in the energy range of 0.5 to 100 GeV, the efficiency of the photon identification can reach 90% with purity of 90%.     

Computer-generated-hologram-accelerated computing method based on mixed programming

Component object model technology is used to solve problems encountered when using three-dimentional （3D） objects to conduct computer-generated hologram （CGH） fast coding. MATLAB and C/C＋＋ are combined for relevant programming under experimental conditions. The proposed method effectively reduces the time required for holographic encoding of large amounts of 3D object data. The CGH- accelerated computing method based on mixed programming is proven to be highly reliable and practical by testing the 3D data of different data volumes. According to the test results, the proposed method improves the efficiency of holographic encoding. The higher the data volume is, the more significantly the computation speed is improved.     

Polarization Properties of Quantum-Dot-Based Single Photon Sources

Polarization properties of single photons emitted by optical pumping from a single quantum dot （ QD） are studied by using a four-level system model. The model is capable of explaining the polarization uncertainty observed in single photon emission experiments. It is found that the dependence of photon emission efficiency and polarization visibility on pump power are opposite in general cases. By employing QDs with small size and strong carrier confinement, the photon polarization visibility under high pump power can be improved. In addition, embedding a QD into a well designed microcavity is also found to be favourable, whereas the trade-off between high polarization visibility and multi-photon emission is noted.     

Gate-modulated generation–recombination current in n-type metal–oxide–semiconductor field-effect transistor

Gate-modulated generation–recombination（GMGR） current IGMGRinduced by the interface traps in an n-type metal–oxide–semiconductor field-effect transistor（n MOSFET） is investigated. The generation current is found to expand rightwards with increasing the reversed drain PN junction bias, and the recombination current is enhanced as the forward drain bias increases. The variations of IGMGRcurves are ascribed to the changes of the electron density and hole density at the interface, NSand PS, under the different drain bias voltages. Based on an analysis of the physical mechanism, the IGMGR model is set up by introducing two coefficients（m and t）. The coefficients m and t can modulate the curves widths and peak values. The simulated results under reverse mode and forward mode are obviously in agreement with the experimental results. This proves that this model can be applicable for generation current and recombination current and that the theory behind the model is reasonable. The details of the relevant mechanism are given in the paper.     

Correlated Photon Pair Generation in Silicon Wire Waveguides at 1.5 μm

Correlated photon pairs at 1.5 μm are generated in a silicon wire waveguide （SWW） with a length of only 1.6 mm. Experimental results show that the single-side count rates on both sides increase quadratically with pump light, indicating that photons are generated from the spontaneous four-wave mixing （SFWM） processes. The quantum correlation property of the generated photons is demonstrated by the ratio between coincident and accidental coincident count rates. The highest ratio measured at room temperature is to be about 19, showing that generated photon pairs have strong quantum correlation property and low noise. What is more, the wavelength correlation property of the coincident count is also measured to demonstrate the correlated photon pair generation. The experimental results demonstrate that SWWs have great potential in on-chip integrated low-noise correlated photon pair sources at 1.5 μm.     

Experimental study of K-shell X-ray emission generated from nanowire target irradiated by relativistic laser pulses

K-shell X-ray emission from a Cu nanowire target irradiated by an ultraintense femtosecond laser pulse is studied using an elliptically bent quartz crystal and imaging plate. The designed bent crystal spectrometer has better spectral resolution, which is higher than 1 000. The absolute Kα radiation photon yields are obtained from the experimental results and the Monte-Carlo model. The conversion efficiency of the Cu Kα line is estimated to be 0.019% from the interaction of 4 J, 50-fs laser pulse irradiated on a Cu nanowire target. The high yield of K shell X-ray has important applications in X-ray emission source.     

Crystal structures and decomposing of B–P compounds under pressure

We have systematically studied the structures, electronic properties, and lattice dynamics of B–P compounds at high pressures. BP and B_6 P are found to be thermodynamically stable below 100 GPa, and other stoichiometries are decomposable under pressure. The predicted structures of F-43 m BP and R-3 m B_6 P are in good agreement with the experimental results by comparing the powder diffraction file(PDF) standard cards with our simulated x-ray diffractions. The bonding properties of BP and B_6 P have also been analyzed by electronic localization functions, charge density difference, and Bader charge analysis. Our results show that BP and B_6 P decompose into B and P under high pressure, which is proven to be dominated by the volumes of them. Furthermore, the infrared and Raman spectra of F-43 m and R-3 m are investigated at selected pressures and will provide useful information for future experimental studies about B–P compounds.     

The analysis of the integral gated mode single photon detector

This paper critically analyses and simulates the circuit configuration of the integral gated mode single photon detector which is proposed for eliminating the transient spikes problem of conventional gated mode single photon detector. The relationship between the values of the circuit elements and the effect of transient spikes cancellation has been obtained. With particular emphasis, the bias voltage of the avalanche photodiode and the output signal voltage of the integrator have been calculated. The obtained analysis results indicate that the output signal voltage of the integrator only relates to the total quantity of electricity of the avalanche charges by choosing the correct values of the circuit elements and integral time interval. These results can be used to optimize the performance of single photon detectors and provide guides for the design of single photon detectors.     

Theoretical analysis on the efficiency of optical-optical double-color double-resonance multiphoton ionization

Analytic formula of the efficiency of optical-optical double-color double-resonance multi-photon ionization （OODR-MPI） is derived from the dynamic rate equation about the interaction of photon and material. Based on this formula, the influence of characteristic of the pump and probe laser on the ionization efficiency of （1＋2＋1） OODR-MPI process is simulated theoretically. It is shown that the pump laser will affect the ionization efficiency by the number control of the molecules excited to the first resonance state. The ionization efficiency is decided by the probe laser directly. Both of the excited molecules and ionization efficiency increase with the intensity and pulse duration of the laser until saturation. It is also found that the longer the delay time of the probe laser to the pump one is, the lower the ionization efficiency would be. The delay time ought to be smaller than the lifetime of the excited molecule in the practical use of the OODR-MPI technique.     

Fluorescence spectrum,thermal properties,and continuous-wave laser performance of the mixed crystal Nd：Lu0.99La0.01 VO4

The fluorescence spectrum and thermal properties of the mixed crystal Nd：Luo.gvLa~.o1VO4 are determined. The strongest emission peak located at 1065.6 nm had a full width at half maximum （FWHM） of 2.1 nm. Continuous-wave （CW） laser performance is demonstrated by a compact planar planar cavity that is end- pumped by a diode laser. The laser output characteristics are investigated by using output couplers with different transmissions. A maximum CW output power of 8.09 W was obtained at an incident pump power of 19.4 W, which corresponds to an optical-to-optical conversion efficiency of 41.7% and a slope efficiency of 54.6%. The dependence of optimum transmission on pump power is calculated theoretically and is found to be consistent with experimental results.     

Correlation between microbubble-induced acoustic cavitation and hemolysis in vitro

Microbubbles promise to enhance the efficiency of ultrasound-mediated drug delivery and gene therapy by taking advantage of artificial cavitation nuclei.The purpose of this study is to examine the ultrasound-induced hemolysis in the application of drug delivery in the presence of microbubbles.To achieve this goal,human red blood cells mixed with microbubbles were exposed to 1-MHz pulsed ultrasound.The hemolysis level was measured by a flow cytometry,and the cavitation dose was detected by a passive cavitation detecting system.The results demonstrate that larger cavitation dose would be generated with the increase of acoustic pressure,which might give rise to the enhancement of hemolysis.Besides the experimental observations,the acoustic pressure dependence of the radial oscillation of microbubble was theoretically estimated.The comparison between the experimental and calculation results indicates that the hemolysis should be highly correlated to the acoustic cavitation.     

Statistical analysis of the temporal single-photon response of superconducting nanowire single photon detection

A new method to study the transient detection efficiency(DE) and pulse amplitude of superconducting nanowire single photon detectors(SNSPD) during the current recovery process is proposed — statistically analyzing the single photon response under photon illumination with a high repetition rate.The transient DE results match well with the DEs deduced from the static current dependence of DE combined with the waveform of a single-photon detection event.This proves that static measurement results can be used to analyze the transient current recovery process after a detection event.The results are relevant for understanding the current recovery process of SNSPDs after a detection event and for determining the counting rate of SNSPDs.     

Single-Photon Emission at Liquid Nitrogen Temperature from a Single InAs/GaAs Quantum Dot

We report on the single photon emission from single InAs/GaAs self-assembled Stranski-Krastanow quantum dots up to 80 K under pulsed and continuous wave excitations. At temperature 8OK, the second-order correlation function at zero time delay, g^（2）（0）, is measured to be 0.422 for pulsed excitation. At the same temperature under continuous wave excitation, the photon antibunching effect is observed. Thus, our experimental results demonstrate a promising potential application of self-assembled InAs/GaAs quantum dots in single photon emission at liquid nitrogen temperature.     

Residual Doppler Effect on Electromagnetically Induced Transparency in a Zeeman Sublevel System

We investigate the residual Doppler effect on the linewidth of electromagnetieally induced transparency （EIT） in a Zeeman sublevel system where a careful experimental design ensures the smallest measurement error. The overall measurement error of the EIT linewidth is estimated to be less than 5%. We present the linear dependence of EIT resonance broadening at small angular deviation in detail. The theoretical analysis exploits the dependence of this feature and shows the qualitative agreement between numerical results and experimental results.