微型化自由运行InGaAs/InP单光子探测器(特邀)

单光子探测器具有最高的光探测灵敏度,在激光雷达系统中使用单光子探测器可以极大提升系统的综合性能。近红外二区(1.0~1.7μm)激光具有大气透过率高、散射弱、太阳背景辐射弱等优势,是大气遥感、三维成像等激光雷达系统的理想工作波段。研制了一种基于InGaAs/InP负反馈雪崩光电二极管的微型化自由运行单光子探测器。该探测器长宽高为116 mm×107.5 mm×80 mm,在1.5μm最大探测效率超过35%,时间抖动(半高宽)低至80 ps。为满足激光雷达系统对光子飞行时间测量的需求,探测器内部集成时间数字转换(TDC)功能,时间精度100 ps。同时,探测器集成一套后脉冲修正及计数率修正算法,可以有效降低探测器所引起的雷达信号畸变。

自由光子的态函数

利用Schrodinger方程和相对论关系式,我们发现对于自由光子,Schrodinger方程等效于Maxwell方程;通过尝试构建自由光子的态函数,既可以描述自由光子的量子性质,又可以表达光波的经典宏观性质(电磁性质和干涉衍射)。

自由中微子的相对论

根据自由微观粒子的相对论质量与速度的关系,分别给出自由微观粒子和自由光子的相对论能量表示;根据自由中微子的定义、动量守恒定律和能量守恒定律,给出自由中微子的静止质量、速度和相对论能量表示。结果表明:1个自由光子的能量为2个相互耦合的自由中微子能量之和,即E(c)=2E(v_n);自由中微子的运动速度和静止质量分别为v_n=c,m_(n0)=m_0/2。

光子动量-偏振两自由度逻辑Bell态测量

量子逻辑编码是提高量子系统抗噪声能力的一种有效方法.相较于单自由度多光子逻辑编码方式,单光子多个自由度的逻辑编码方式更为简洁且能够节约光子资源.本文利用线性光学元件提出了两种光子动量-偏振两自由度逻辑Bell态测量方案:辅助W态的逻辑Bell态测量方案和自辅助逻辑Bell态测量方案.在第一个方案中,通过辅助四光子W态对两光子的两个自由度同时进行宇称测量,并根据光子探测器的响应情况得到偶宇称逻辑Bell态的测量结果,成功率为12.5%.在第二个方案中,利用简单的线性光学元件和光子探测器能够从四个逻辑Bell态中完全区分出两个偶宇称逻辑Bell态,且成功率提高为50%.相较于非线性光学方案,这两种基于线性光学的逻辑Bell态测量方案更加容易实验实现,因此在量子通信中有非常重要的应用.

带轴向引导磁场自由电子激光的单粒子哈密顿理论

在Ｂａｍｂｉｎｉ－Ｒｅｎｉｅｒｉ坐标系中给出了带轴向引导磁场自由电子激光的单粒子哈密顿形式．得到了轴向场对器件增益放大系数的表达式，并讨论了对轴向场取值的一些限制条件．

Characteristic analysis of 1.06μm long-cavity diode lasers based on asymmetric waveguide structures

In long-cavity edge-emitting diode lasers,longitudinal spatial hole burning(LSHB),two-photon ab⁃sorption(TPA)and free carrier absorption(FCA)are among the key factors that affect the linear increase in out⁃put power at high injection currents.In this paper,a simplified numerical analysis model is proposed for 1.06μm long-cavity diode lasers by combining TPA and FCA losses with one-dimensional(1D)rate equations.The ef⁃fects of LSHB,TPA and FCA on the output characteristics are systematically analyzed,and it is proposed that ad⁃justing the front facet reflectivity and the position of the quantum well(QW)in the waveguide layer can improve the front facet output power.

水下光场的蒙特卡罗法求解

水下光场分布对水下光电成像质量具有决定性的影响,通过水下光场分布可以得到水下图像的传输退化模型。在给定水体光学参数的前提下,建立光子水下传输概率模型,利用Monte Carlo法模拟光子在水下的运动,可以获得水下光子散射点体积密度分布,求解出水下光场;在水体体散射函数为球形对称的条件下,利用Monte Carlo法得到的水下光场分布与理论公式的计算结果具有很好的一致性,验证了该方法的有效性;最后给出了水下理想点光源形成的水下光场分布。基于此结论,可以将Monte Carlo法求解水下光场的应用范围推广至水体体散射函数为一般表达式的情形。

基于计算机仿真的复合光功能树脂的设计

基于计算机仿真技术,结合蒙特卡罗算法和光学理论,研究了荧光粒子粒径和用量对复合光功能树脂光通量、相关色温、光子平均自由程和色坐标等的影响规律。结果表明:复合光功能树脂的光通量随着荧光粒子粒径的增大先升高后降低,相关色温和光子平均自由程则由于粒子数目降低而逐渐升高,在粒径为9μm时具有最大光通量(150.69 lm);复合光功能树脂的光通量随着荧光粒子用量的增加先升高后降低,相关色温和光子平均自由程则由于粒子数目升高而逐渐降低,在荧光粒子质量分数为8.5%时具有最大光通量(149.26 lm)。进一步结合色坐标与黑体辐射曲线的相对位置得到荧光粒子最佳粒径为12μm,最佳用量为6.0%(w),此时对应色坐标x=0.379 1,y=0.383 2,相关色温4 588 K,光通量144.95 lm。

Quantum Secure Direct Communication by Using Three-Dimensional Hyperentanglement

We propose two schemes for realizing quantum secure direct communication (QSDC)by using a set ofordered two-photon three-dimensional hyperentangled states entangled in two degrees of freedom (DOFs)as quantuminformation channels.In the first scheme,the photons from Bob to Alice are transmitted only once.After insuring thesecurity of the quantum channels,Bob encodes the secret message on his photons.Then Alice performs single-photontwo-DOF Bell bases measurements on her photons.This scheme has better security than former QSDC protocols.In thesecond scheme,Bob transmits photons to Alice twice.After insuring the security of the quantum channels,Bob encodesthe secret message on his photons.Then Alice performs two-photon Bell bases measurements on each DOF.The schemehas more information capacity than former QSDC protocols.

Application of Laser Dispersion Method in Apparatus Combining H Atom Rydberg Tagging Time-of-Flight Technique with Vacuum Ultraviolet Free Electron Laser

Photodissociation of H2S in the VUV region plays an important role in the atmospheric chemistry and interstellar chemistry.To date,however,few studies have been focused on this topic.In this article,we have described a laser dispersion method applied in the apparatus combining the high-n H atom Rydberg tagging time-of-flight technique with the vacuum ultraviolet free electron laser(VUV FEL).The Lyman-αlaser beam(121.6 nm)used in the H-atom detection was generated by the difference frequency four-wave mixing schemes in a Kr/Ar gas cell.After passing through an off-axis biconvex LiF lens,the 121.6 nm beam was dispersed from the 212.6 nm and 845 nm beams due to the different deflection angles experienced by these laser beams at the surfaces of the biconvex lens.This method can eliminate the background signal from the 212.6 nm photolysis.Combined with the VUV FEL,photodissociation of H2S at 122.95 nm was studied successfully.The TOF spectrum was measured and the derived total kinetic energy release spectrum was displayed.The results suggest that the experimental setup is a powerful tool for investigating photodissociation dynamics of molecules in the VUV region which involves the H-atom elimination processes.

Infrared Spectroscopy of Neutral Clusters Based on a Vacuum Ultraviolet Free Electron Laseri

Spectroscopic characterization of clusters is crucial to understanding the structures and reaction mechanisms at the microscopic level,but it has been proven to be a grand challenge for neutral clusters because the absence of a charge makes it di伍cult for the size selection and detection.Infrared(IR)spectroscopy based on threshold photoionization using a tunable vacuum ultraviolet free electron laser(VUV-FEL)has recently been developed in the lab.The IR-VUV depletion and IR+VUV enhancement spectroscopic techniques open new avenues for size-selected IR spectroscopies of a large variety of neutral clusters without confinement(i.e.,an ultraviolet chromophore,a messenger tag,or a host matrix).The spectroscopic principles have been demonstrated by investigations of some neutral water clusters and some metal carbonyls.Here,the spectroscopic principles and their applications for neutral clusters are reviewed.

Free electron laser based on the Smith-Purcell radiation

A Smith-Purcell （SP） free electron laser （FEL） ,composed of a metallic diffraction flat grating,an open cylindrical mirror cavity and a relativistic sheet electron beam with moderate energy, is presented. The characteristics of this device are studied by theoretical analysis,experimental measurements and particle-in-cell （PIO） simulation method. Results indicate that the coherent radiation with an output peak power up to 50 MW at millimeter wavelengths can be generated by using relativistic electron beam of moderate energy.

Vacuum Ultraviolet Free-Electron Laser Photoionization Mass Spectrometry of Alpha-pinene Ozonolysis

α-pinene is the most abundant monoterpene that represents an important family of volatile organic compounds.Molecular identification of key transient compounds during theα-pinene ozonolysis has been proven to be a challenging experimental target because of a large number of intermediates and products involved.Here we exploit the recently developed hybrid instruments that integrate aerosol mass spectrometry with a vacuum ultraviolet free-electron laser to study theα-pinene ozonolysis.The experiments ofα-pinene ozonolysis are performed in an indoor smog chamber,with reactor having a volume of 2 m^(3) which is made of fluorinated ethylene propylene film.Distinct mass spectral peaks provide direct experimental signatures of previously unseen compounds produced from the reaction ofα-pinene with O_(3).With the aid of quantum chemical calculations,plausible mechanisms for the formation of these new compounds are proposed.These findings provide crucial information on fundamental understanding of the initial steps ofα-pinene oxidation and the subsequent processes of new particle formation.

Grover量子搜寻算法的线性光学实现

利用线性光学元件和单光子来编码量子比特,可给出Grover量子搜寻算法的光学实现方案。该方案可以推广到多个量子比特的情况。

Free radical scavenging abilities of polypeptide from Chlamys farreri

We investigated the radical scavenging effect and antioxidation property of polypeptide ex- tracted from Chlamys farreri (PCF) in vitro using chemiluminescence and electron spin resonance (ESR) methods. We examined the scavenging effects of PCF on superoxide anions ( O?2 ), hydroxyl radicals (OH·), peroxynitrite (ONOO-) and the inhibiting capacity of PCF on peroxidation of linoleic acid. Our experiment suggested that PCF could scavenge oxygen free radicals including superoxide anions ( O2? ) (IC50 =0.3 mg/ml), hydroxyl radicals (OH·) (IC50 = 0.2 μg/ml) generated from the reaction systems and effectively inhibit the oxidative activity of ONOO- (IC50 = 0.2 mg/ml). At 1.25 mg/ml of PCF, the inhibi- tion ratio on lipid peroxidation of linoleic acid was 43 %. The scavenging effect of PCF on O?2 , OH· and ONOO- free radicals were stronger than those of vitamin C but less on lipid peroxidation of linoleic acid. Thus PCF could scavenge free radicals and inhibit the peroxidation of linoleic acid in vitro. It is an anti- oxidant from marine products and potential for industrial production in future.

UV Photodissociation Dynamics of Nitric Acid： The Hydroxyl Elimination Channel

Sliced velocity mapping ion imaging technique was employed to investigate the dynamics of the hydroxyl elimination channel in the photodissociaiton of nitric acid in the ultraviolet region. The OH product was detected by （2＋1） resonance enhanced multiphoton ionization via the D^2∑^- electronic state. The total kinetic energy spectra of the OH＋NO2 channel from the photolysis of HONO2 show that both ：NO2（X2A1） and NO2（A2B2） channels are present, suggesting that both 1^1A″ and 2^1A″ excited electronic states of HONO2 are involved in the excitation. The parallel angular distributions suggest that the dissociation of the nitric acid is a fast process in comparison with the rotational period of the HNO3 molecule. The anisotropy parameter β for the hydroxyl elimination channel is found to be dependent on the OH product rotational state as well as the photolysis energy.

Multi-objective Genetic Optimization for LCLS-II X-ray FEL

The LCLS-II （linac coherent light source II） will build on the success of the world＇s most powerful X-ray laser： the LCLS （linac coherent light source）. It will add two new X-ray laser beams and room for additional new instruments, thus greatly increasing the number of experiments carried out each year. Multiple operation modes are proposed to accommodate a variety of user requirements. There are a large number of variables and objectives in the design. For each operation mode, MOGA （multi-objective genetic algorithm） is applied to optimize the machine parameters in order to minimize the jitters, energy spread, collective effects and emittance.

Numerical Investigations of Transverse Gradient Undulator Based on Novel Light Sources

With the stat-of-the-art laser technique, the quality of electron beam generated from LPA （laser-plasma accelerator） is now becoming much better. The natural merits of electron beam from LPA, e.g., high peak current, ultra-low emittance and ultra-short bunch length, etc., pave the way to the novel light sources, especially in the realm of developing much more compact x-ray light sources, e.g., table-top XFEL （x-ray free-electron laser）. However, the radiation power is limited by the rather larger energy spread than conventional radio-frequency electron LINAC （linear accelerator）. Luckily, much more power could be extracted by using the undulator with transverse gradient when energy spread effect could be compensated. In this paper, we introduce a novel soit x-ray light source driven by LPA together with TGU （transverse gradient undulator） technique, meanwhile we present a simple idea on how to achieve much higher rep-rate （e.g., -100 kHz） FELs （free-electron lasers） boosted by TGU based on storage rings.

Generation of Four-Mode Cluster-Type Entangled Coherent States in Free-Traveling Optical Fields

In this paper, we propose an optical scheme to generate four-mode cluster-type entangled coherent states （ECSs） in free traveling optical fields by using two single-photon sources, coherent state sources, beam splitters, pho- todetectors, cross-Kerr media, and phase shifters. And the success probability of the states preparation is calculated. At last we discuss the experimental feasibility of such proposal.

Red Electrophoretic Particles Based on Fe_2O_3 Nanoparticles for Electronic Inks: Design, Preparation and Properties

In order to modify inorganic particles as chromatic electrophoretic particles, an approach was designed and used to prepare Fe203 red electrophoretic particles. These Fe203-cationic hybrid nanoparticles （Fe203-CHNPs）were prepared through Fe203 core covered with polymer shell which was composed of SiO2 and P （DMAEMA-co-HMA） by using atom transfer radical polymerization （ATRP）technique. The SiO：-coating could introduce the functional group on the surfaceof inorganic particles, through which the polymer shell could be formed by using ATRP tech- nique. The results of Fourier transform infrared spectra （FT-IR）, X-ray photoelectron spectroscopy （XPS） and thermal gravimetric analysis （TGA）confirmed the chemical compositions of Fe2O3-CHNPs; the images of transmission elec- tron microscopy （TEM） indicated the core-shell structure of Fe2O3-CHNPs; the measurements of dynamic light scatter- ing （DLS） showed a 253.7 nm average particle size with narrow size distribution; and the zeta potential measurements identified the high chargeability of Fe2O3-CHNPs. Furthermore, the resulting nanoparticles were successfully applied in the electrophoretic display cell, which demonstrated that it was an effective approach to preparing chromatic elec- trophoretic particles.