光孤子通信系统的研究

光孤子（或超短光脉冲）的获得为光纤通信提供了一种非常高的速度。但是，光孤子之间的非线性作用大大限制了其通讯速度。在本文中，分析了光孤子相互作用对光通讯的影响，并提出了利用光放大及光压缩技术来消除损耗和光子间非线性作用的方案，该方法不仅能提高光通讯的比特率，且能够加大其通讯的距离。通常，在通讯距离给定的情况下，通讯系统的比特率可提高４０％以上。     

浅论光孤子通信技术

光孤子通信利用光纤非线性来抵消光纤色散效应,是下一代超高速、长距离、超大容量光纤通信的优选技术。因此,介绍光孤子通信技术的概念和所具有的优越性,从理论上阐明光孤子在光纤通信中部分关键技术;并且归纳光孤子通信技术的应用前景。     

基于空间光孤子的温度传感器原理

提出一种基于非局域空间光孤子传输的温度传感器的理论方案。得出在环境温度0.32℃的改变就可以引起孤子π相移的结论。此温度改变对相移的调制有望为基于干涉仪原理的温度传感器提供一个可行且灵敏度较高的实现方案。     

光孤子在光纤通信的基本应用

介绍了光孤子的产生、光孤子通信的基本原理、关键技术及其光孤子通信系统构成,展望了光孤子通信的前景。     

2.5Gb/s,52km的光孤子通信实验系统

在国内首次进行了孤子通信的误码测量，成功地将２．５Ｇｂ／ｓ的孤子传输了５２ｋｍ，经过２小时测量无误码。对实验中的现象进行了理论分析。     

光孤子通信系统的色散控制研究

光纤色散特性是支撑光纤孤子通信的决定性因素。比较了目前的几种色散补偿方案后,着重对相位共轭控制的色散控制方式进行了分析研究,该方式利用光纤非线性四波混频产生与输入光脉冲信号相位共轭的输出光脉冲信号,光脉冲的频谱以泵浦光频为中心进行反转,构建成相位共轭器,实现了对放大自发辐射(ASE)噪声、孤子相互作用与色散波等的控制,达到提高系统传输速率、距离和通信容量的目的。     

光空间调制技术的研究进展

光空间调制(OSM)作为一种新型的光多输入多输出(OMIMO)技术,利用空间域激光器索引号额外携带信息,有效地提高了系统的传输速率和能量效率;同时,由于每符号周期仅激活一个激光器传递信息,较好地解决了传统OMIMO系统中的信道干扰和同步等问题。本文首先介绍了现有的几种光空间调制技术,概括和总结其在国内外的研究现状。此外,从传输速率、频谱效率、误码率(BER)和计算复杂度等四个方面对现有的OSM、光空移键控(OSSK)、增强型光空间调制(EOSM)和差分光空间调制(DOSM)等方案进行了比较分析。最后,指出了OSM中亟需解决的关键性问题及其未来的发展方向。     

光纤中光孤子传输演化及相互作用研究

基于非线性薛定谔方程,采用分步傅立叶方法模拟了基阶、二阶和三阶皮秒光孤子以及光孤子对在光纤中的传输演化.结果表明,在长距离传输过程中基阶孤子的幅度和脉宽基本不变,是进行光孤子通信的理想载体.高阶孤子的幅度和脉宽变化较大,并呈现一种周期性的变化;孤子对的传输与两个脉冲的初始相位和输入强度相关.考虑三阶色散的飞秒量级孤子在光纤中的传输将不再出现对称性和周期性,脉冲的中心位置将发生偏移,同时脉冲的波形也会发生扭曲.     

基于非机械调制光的激光测振仪校准技术进展

随着激光测振仪使用场景和测量范围的不断扩大,其校准也愈发重要。但依据目前测振仪校准标准,无法实现高频高速环境下的整机校准,因此迫切需求完善此方面的校准方法。近几年,研究人员将非机械调制光用于测振仪校准测试中,构建了理论模型并取得了校准试验数据。本文对这些理论模型和试验数据进行了分析,根据光调制产生位置和核心调制器件的不同对相关方法进行了分类,同时对其工作原理、系统结构组成和主要参数等进行介绍,再对比分析不同方法的校准功能与适用范围,最后展望了相关方法的发展潜力和研究方向,为测振仪校准技术进一步研究提供了借鉴。     

量子态隐形传输创新纪录

<正>有历史学家总结:18世纪至19世纪是机械世纪,20世纪是信息时代,现在的21世纪是量子世纪。据物理学家组织网9月5日报道,维也纳大学和奥地利科学院的物理学家实现了量子态隐形传输最远距离143公里,创造了新的世界纪录。该实验向基于卫星的量子通信迈出了重要一步。相关研究结果发表在最新一期《自然》杂志上。     

Optical protocol for quantum state sharing of superposed coherent state

We propose an optical protocol for quantum state sharing of superposed coherent state in terms optical elements. Our protocol can realize a near-complete quantum state sharing of a superposed coherent state with arbitrary coeficients. The realization of this protocol is appealing due to the fact that the quantum state of light is robust against the decoherence and photons are ideal carriers for transmitting quantum information over long distances. This protocol can also be generalized to the multiparty system.     

Influences of silicon doping in quantum dot layers on optical characteristics of InAs/GaAs quantum dot infrared photodetector

We have investigated the effects of silicon doping concentration within thirty-period self-assembled quantum dot (QD) layers on quantum dot infrared photodetectors (QDIPs). The lens-shaped quantum dots with the dot density of 1 × 10¹¹ cm^− 2 were observed by atomic force microscope (AFM). From the high ratio of photoluminescence (PL) peak intensities from dot layer to that from wetting layer, we have concluded that high dot density caused the short diffusion length for carriers to be easily captured by QDs. Moreover, the Si-doped samples exhibited the multi-state transitions within the quantum dots, which were different to the single level transition of undoped sample. Besides, the dominant PL peaks of Si-doped samples were red-shifted by about 25 meV compared to that of the undoped sample. It should result from the dopant-induced lowest transition state and therefore, the energy difference should be equal to the binding energy of Si in InAs QDs.     

自由空间量子密钥分发中的信号同步解决方案

针对目前自由空间量子密钥分发（QKD）中的信号同步这一难点问题,提出一种采用外置光信号来解决信号同步问题的方案——光同步方案。在发送端利用声光调制器将外置激光器的连续激光分割成周期光脉冲序列,并作为同步光信号发送给接收端。接收端采用光电倍增管接收同步光脉冲信号,生成一个与发送端严格同步的信号,以此作为接收端的时基标准来进行单光子计数。采用高频的内部时钟信号来“监视”接收到的同步信号,从而提高计数准确性。该方案具有长距离性、无线性、低复杂度等特点,已成功应用于一个基于B92协议的自由空间QKD系统中。     

Structural and optical characteristics of InN/GaN multiple quantum wells grown by metalorganic chemical vapor deposition

The structural and electrical properties of InN/GaN multiple quantum wells, which were grown by metalorganic chemical vapor deposition, were characterized by transmission electron microscopy (TEM) and electroluminescence measurements. From the TEM micrographs, it was shown that the well layer was grown like a quantum dot. The well layer is expected to be the nano-size structures in the InN multiple quantum well layers. The multi-photon confocal laser scanning microscopy was used to investigate the optical properties of the light emitting diode (LED) structures with InN active layers. It was found that the two-photon excitation was possible in InN system. The pit density was measured by using the far-field optical technique. In the varied current conditions, the blue LED with the InN multiple quantum well structures did not have the wavelength shift. With this result, we can expect that the white LEDs with the InN multiple quantum well structures do not show the color temperature changes with the variations of applied currents.     

Temperature dependent optical properties of stacked InGaAs/GaAs quantum rings

In this paper we describe the results of temperature dependent photoluminescence intensity and decay time measurements of In(Ga)As/GaAs quantum rings where the depth of barrier is varied from sample to sample. The activation energy found for the reduction of the exciton decay time as a function of the temperature is approximately half the value of the thermionic escape energy of excitons. The temperature dependant behaviour is ascribed to the carriers lost via the excited state to the WL.

The time resolved PL study indicates that thermal escape mechanisms is not so affected by reducing the spacer thickness, but it's influenced essentially by the excited state recombination.     

Interface/surface optical phonon in onion-like quantum dots

We calculate the interface/surface phonon in onion-like quantum dots by using dielectric continuum approach. The form of the phonon potential of the onion-like quantum dots and the electron-phonon interaction Hamiltonian are obtained. Core/shell quantum dots and quantum dot quantum well are studied in detail. The interface/surface phonon modes and corresponding frequencies as a function of the sizes of the structure are investigated. We observe that the asymptotic behavior is depended on the host medium. The sensitivity of the interface/surface phonon frequencies are decreasing with the increasing of the shell thickness. The contribution of different angular momentum quantum numbers to the electron-phonon interaction are given for the onion-like quantum dots. Numerical calculations are performed on the CdS/ZnS and CdS/ZnS/CdS heterostructure which is embedded in the polyethylene.     

Radiative interface state study in CdSe/ZnS quantum dots covered by polymer

The paper presents the transformation of photoluminescence (PL) spectra of nonconjugated and bioconjugated core/shell CdSe/ZnS QDs covered by PEG polymer at the aging in ambient air. Studied QDs are characterized by the sizes: (i) 3.6-4.0 nm and color emission with the maxima at 560-565 nm (2.19-2.25 eV) and (ii) 5.2-5.3 nm and with emission at 605-610 nm (2.02-2.08 eV). The part of 565 nm CdSe/ZnS QDs has been bioconjugated to the mouse anti PSA (Prostate-Specific Antigen) antibodies and the part of 605 nm QDs has been bioconjugated to the antihuman IL10 (Interleukin 10) antibodies using the commercially available 565 nm and 605 nm QD conjugation kits. It is revealed that the aging process in ambient air has the very strong impact on PL spectra of nonconjugated core/shell CdSe/ZnS QDs covered with PEG polymer. The aging process relates to the polymer modification in ambient air that is accompanied by the three effects: (i) polymer transparency increasing for the emission of CdSe cores (2.03 or 2.20 eV), (ii) the intensity stimulation of high energy PL bands (2.37, 2.73 and 3.06 eV) related to the interface states at the ZnS/PEG polymer interface and (iii) the elastic strain modification in QD systems. The concentration of interface states at the ZnS/polymer interface increases at the aging of PEG polymer in ambient air.     

Measurement-device-independent quantum key distribution with odd coherent state

Measurement-device-independent quantum key distribution (MDI-QKD) is immune to all the detection attacks, thus when it is combined with the decoy-state method, the final key rate can be obtained by estimating the gain and quantum bit error rate for various input photon numbers. In this paper, we propose to perform MDI-QKD with odd coherent state (OCS) and compare the results with weak coherent source scenario. Our simulation indicates that both the secure key rate and transmission distance can be improved evidently with OCS owing to the lower probability of multi-photon events of the OCS. Furthermore, we apply the finite key analysis to the decoy-state MDI-QKD with OCS and obtain a practical key rate.     

Surface optical phonon-assisted electron Raman scattering in a free-standing quantum wire with ring geometry

We present a theoretical calculation of the differential cross section for the electron Raman scattering process associated with surface optical phonon modes in semiconductor quantum wires (QWs) with ring geometry. Electron states are considered to be confined within the QWs. We consider the Fröhlich electron-phonon interaction in the framework of the dielectric continuum approach. Some singularities for the ring with various sizes in the Raman spectra are found and interpreted. A discussion of the phonon behavior for the QWs with large and small sizes is presented. The numerical results are also compared with those of experiments.