A nonlinear optical-fiber interferometer for nondemolitional measurement of photon number

A nondemolitional measurement scheme to determine the photon number was realised using an optical fiber as the optical Kerr medium. The φ⁽³⁾ value of an optical fiber for the optical Kerr effect was measured using this scheme. A classical correlation between the measured light intensity and the outgoing light intensity was observed experimentally. The goal of the measurement accuracy to obtain a quantum correlation is also discussed aiming at the quantum nondemolition (QND) measurement of the photon number.     

Investigation of high-speed optical FSK generation scheme based on carrier suppression and phase modulation

We propose and numerically investigate a novel high-speed (40-Gb/s and above) optical frequency shift-keying (FSK) transmitter scheme. By optical carrier-suppressed modulation and differential phase-shift-keying (DPSK) to intensity modulation (IM) conversion, only one light source is needed in the proposed scheme to generate high-speed optical FSK signals. By using a Mach-Zehnder modulator (MZM) as phase modulator and an additional delay interferometer (DI) cascaded after the carrier-suppressed MZM to suppress the remaining carrier, the performance of our scheme can compete with the double-light-source counterparts. The transmission performances of the FSK signal generated with the proposed scheme as well as detuning and bandwidth tolerance of the demodulation filter are also carefully investigated. Simulation results show that the proposed FSK generation scheme is very suitable for the next-generation optical access network and optical label switching network. A potential application of our scheme in high-speed passive optical network is proposed.     

用液晶空间光调制器产生光阱阵列

液晶空间光调制器能够方便地用于制作各种衍射型光学元件, 但液晶空间光调制器存在分辨率有限的缺点, 本文提出了用液晶空间光调制器制作相位型光栅, 产生一维和二维光阱阵列的新方案, 用迭代傅里叶级数算法优化设计光栅的相位分布, 在不改变空间光调制器硬件参数设置的情况下, 充分利用和发掘了空间光调制器的优点, 同时又能较好地回避其所存在的缺陷. 根据现有的空间光调制器的技术参数, 模拟仿真设计光栅, 计算光强分布, 结果表明: 用大失谐、小功率激光照明, 能够产生具有很高峰值光强和光强梯度的光阱阵列, 囚禁冷原子的光学偶极势达到mK量级, 对原子的作用力远大于原子的重力.     

Spatial Fourier-decomposition optical fluorescen tomography-theoretical investigation

A new three-dimensional (3D) optical fluorescent tomographic imaging scheme is proposed with structured illumination and spatial Fourierdomain decomposition methods for the first time. In this spatial Fourier-decomposition optical fluorescence tomography (SF-OFT), the intensity of focused excitation light from an objective lens is modulated to be a cosine function along the optical axis of the system. For a given position in a two-dimensional (2D) raster scanning process, the spatial frequency of the cosine function along the optical axis sweeps in a proper range while a series of fluorescence intensity are detected accordingly. By making an inverse discrete cosine transformation of these recorded intensity profiles, the distribution of fluorescent markers along the optical axis of a focused laser beam is obtained. A 3D optical fluorescent tomography can be achieved with this proposed SF-OFT technique with a simple 2D raster scanning process.     

一种新颖的表面光波导型原子(或分子)分束器

提出了一种采用二元π位相板与柱面透镜组合而构成表面光波导型原子（或分子）分束器及其Mach-Zehnder干涉仪与X-分束器列阵的新方案，介绍了本方案的物理思想与基本原理，导出了光强分布、强度梯度、分束距离和分束路径的宽度与光学系统参数间的解析关系，并分析和讨论了本方案的潜在应用及其可行性. 研究表明，本方案设计新颖、光路简单，便于与其他元件组合构成具有表面微结构的集成原子（或分子）光学元器件及其全光型原子（或分子）芯片. 关键词： 原子（或分子）光波导 原子（或分子）分束器 原子（或分子）芯片 二元π位相板     

实现冷原子或冷分子囚禁的可控制光学四阱

提出了一种利用单光束照明二元π相位板与透镜组合系统实现冷原子或冷分子囚禁的可控制光学四阱新方案.计算了四阱的光强分布，讨论了从光学四阱到双阱或到单阱的演化过程，并导出了四阱和双阱几何参数、光强分布、强度梯度及其曲率与光学透镜系统参数间的解析关系.研究表明，通过相对移动二元π相位板可实现光学四阱到双阱或到单阱的连续双向演化，获得了四阱或双阱间距与相位板移动距离的关系.该方案在超冷原子物理、冷分子物理、原子光学、分子光学和量子光学，甚至量子计算及信息处理等领域中有着广阔的应用前景. 关键词： 二元π相位板 可控制光学四阱 原子分子囚禁 原子光学     

产生暗归零码光标记信号的新方案

在对预编码、调制和编码过程进行改进的基础上,提出了一种利用一个双臂马赫-曾德尔铌酸锂调制器和一个电信号时延器产生可调占空比和消光比的光暗脉冲归零码二进制信号的新方案。实验证明这种信号能用传统的二进制强度调制-直接检测系统的接收机进行检测。实验得到了在调节电信号时延器时速率为2.5 Gbit/s的光暗脉冲归零码二进制信号的频谱变化规律,以及占空比分别为0.25,0.35,0.60和0.80时光暗脉冲归零码二进制信号的误码率和眼图。此外,利用该方案产生的光暗脉冲归零码二进制信号可以作为标记在光标记交换网络中得到应用。     

High-repetitive frequency millimeter-wave signal generation using multi-cascaded external modulators based on carrier suppression technique

We have numerically and experimentally investigated how to generate high-repetitive frequency millimeter (mm)-wave using multi-cascaded intensity modulators based on optical carrier suppression (OCS) scheme. We have found the rule how to generate the high-repetitive frequency mm-wave by adjusting the repetitive frequency of the radio-frequency (RF) signals and the phase relation between the RF signals on the intensity modulators. Based on this rule, we have experimentally demonstrated to generate over 80 GHz optical mm-wave.     

Expanding amplitude-squeezing bandwidth with off-peak dispersive optical feedback

Weak dispersive optical feedback has been proved both theoretically and experimentally to be able to reduce the intensity noise of semiconductor lasers and allow the generation of amplitude-squeezed states. I propose a novel scheme exploiting the off-peak optical feedback condition that expands the squeezing bandwidth and significantly enhances the repeatability over the most commonly utilized on-peak optical feedback scheme. Using a realistic model, I show that under the zero-frequency-pulling condition the off-peak scheme greatly enhances the squeezing bandwidth.     

一种新颖的全光型表面原子(分子)漏斗

提出了一种产生全光型表面原子(分子)漏斗的新方案.采用红失谐高斯激光束照明由柱面透镜组成的光学系统，可在透镜焦平面附近产生横向漏斗形光强分布，以构成一表面光波导型原子漏斗.计算了漏斗的光强分布及其光学偶极势与偶极力分布.研究结果表明：该原子漏斗可用于冷原子(分子)的表面光波导、分束器和干涉仪以及微阱囚禁的有效装载，因而在集成原子光学及其原子芯片的研究中有着重要的应用. 关键词： 原子漏斗 分子漏斗 光学偶极势 原子芯片     

Photonic generation of ultra-wideband doublet pulse using a semiconductor-optical-amplifier based polarization-diversified loop

We propose and demonstrate a novel scheme of ultra-wideband (UWB) doublet pulse generation using a semiconductor optical amplifier (SOA) based polarization-diversified loop (PDL) without any assistant light. In our scheme, the incoming gaussian pulse is split into two parts by the PDL, and each of them is intensity modulated by the other due to cross-gain modulation (XGM) in the SOA. Then, both parts are recombined with incoherent summation to form a UWB doublet pulse. Bi-polar UWB doublet pulse generation is demonstrated using an inverted gaussian pulse injection. Moreover, pulse amplitude modulation of UWB doublet is also experimentally demonstrated. Our scheme shows some advantages, such as simple implementation without assistant light and single optical carrier operation with good fiber dispersion tolerance.     

An experimental investigation on two-dimensional shape-based diffuse optical tomography

A two-dimensional （2D） shape-based approach of image reconstruction using a boundary element method is developed for diffuse optical tomography （DOT）. The experimental validation uses a four-channel time- correlated single photon counting （TCSPC） system for detection and an intensity data-type for image reconstruction. The optical and geometric parameters are simultaneously recovered using a difference imaging scheme. Results demonstrate that the proposed DOT modality is a promising methodology of in vivo reconstruction of the optical structures of tissues.     

一种新颖的实现冷原子或冷分子囚禁的可控制光学四阱及其二维光学晶格

原子光学晶格为精确操控中性原子和研究某些基本物理问题提供了一种方法。提出了一种利用单光束照明余弦型振幅光栅与透镜组合系统实现冷原子或冷分子囚禁的可控制光学四阱新方案,计算了四阱的光强分布,讨论了从光学四阱到双阱或单阱的演化过程,并导出了光学四阱的几何参量、光强分布、强度梯度及其曲率与光学透镜系统参量间的解析关系,获得了四阱间距与光栅空间频率的关系。研究表明通过改变余弦光栅的空间频率即可实现从光学四阱到双阱或单阱的连续双向演化。     

采用OFDM信号作为标记的光分组交换方案

以光正交频分复用信号作为光标记,利用两个不同波长的光载波分别经过强度调制,产生了10 Gb/sOOK光载荷和2.5 Gb/sOFDM光标记。测得了光分组信号经光纤传输前后接收载荷的眼图和标记的星座图以及误码率曲线,结果表明:经过40 km光纤传输后,载荷与标记的功率代价分别为1dB和0.5dB。     

通过圆孔衍射实现冷分子(或冷原子)囚禁的光学偶极阱

以单色标量波衍射理论为基础,研究单色平面波由圆孔衍射产生实现冷分子(或冷原子)光学囚禁的光阱。运用圆孔衍射理论分析讨论了光学偶极阱的光强分布、光学势及偶极力,并导出了有关光阱的几何参量、光强分布、强度梯度及其曲率与光学系统参量(如照明光波的波长、小孔的孔径)间的解析关系。研究表明,当激光功率与波长分别为P=500 W和λ=1.08μm,小孔半径a=20μm时,产生囚禁甲烷CH4分子的光阱光学势约为57.9μK。通过圆孔衍射可实现冷分子或冷原子囚禁,该方案不仅简单可行、操作方便,而且在冷分子物理、原子光学、分子光学和量子光学等领域中有着广阔的应用前景。     

Optical cavity coupled surface plasmon resonance sensing for enhanced sensitivity

A surface plasmon resonance (SPR) sensing system based on the optical cavity enhanced detection tech-nique is experimentally demonstrated. A fiber-optic laser cavity is built with a SPR sensor inside. By measuring the laser output power when the cavity is biased near the threshold point, the sensitivity, defined as the dependence of the output optical intensity on the sample variations, can be increased by about one order of magnitude compared to that of the SPR sensor alone under the intensity interrogation scheme. This could facilitate ultra-high sensitivity SPR biosensing applications. Further system miniaturization is possible by using integrated optical components and waveguide SPR sensors.     

Control over hysteresis curves and thresholds of optical bistability in different semiconductor double quantum wells

The effects of optical field on the phenomenon of optical bistability(OB) are investigated in a K-type semiconductor double quantum well(SDQW) under various parametric conditions. It is shown that the OB threshold can be manipulated by increasing the intensity of coupling field. The dependence of the shift of OB hysteresis curve on probe wavelength detuning is then explored. In order to demonstrate controllability of the OB in this SDQW, we compare the OB features of three different configurations which could arise in this SDQW scheme, i.e., K-type, Y-type, and inverted Y-type systems. The controllability of this semiconductor nanostructure medium makes the presented OB scheme more valuable for applications in all-optical switches, information storage, and logic circuits of all optical information processing.     

液晶空间光调制器产生可调三光学势阱

提出了产生三光学势阱的新方案, 在该方案中用液晶空间光调制器制作相位型闪耀光栅, 单色相干光照明, 产生按等边三角形分布的三个光学势阱, 三个光阱光强大小分布相同, 调节空间光调制器的相位分布, 可以改变光阱的相对位置, 实现三光阱到单个光阱、两光阱合并为一个光阱等演变及其反向演变, 调节过程简单、方便. 根据现有空间光调制器性能和尺寸, 模拟设计光栅, 计算三光阱的光强分布和调控过程中光强的变化, 结果表明: 用一般功率的激光照明, 能够得到具有较大峰值光强和较高光强梯度的可调三光阱, 在原子和分子光学实验研究中有多种重要的应用. 关键词： 原子和分子光学 可调三光学势阱 空间光调制器     

Ultrawideband monocycle generation using cross-phase modulation in a semiconductor optical amplifier

We propose a novel scheme to generate ultrawideband (UWB) monocycle pulses based on cross-phase modulation (XPM) of a semiconductor optical amplifier (SOA). The proposed system consists of a SOA and an optical bandpass filter (OBF). Due to the XPM, a continuous wave (CW) probe signal is phase modulated by another optical Gauss pulse in the SOA. The OBF will convert the phase modulation to intensity modulation. A pair of polarity-reversed UWB monocycle pulses is achieved by locating the probe carrier at the positive and negative linear slopes of the OBF. Both cases conform to the UWB definition of the Federal Communications Commission.     

Time-resolved entanglement and photon number correlation of twin beams: Application to quantum key distribution scheme

Quantum entanglement and intensity correlations in continuous variable (CV) regimes have investigated in the time domain in addition to many analogous investigations performed in the frequency domain. The specific signatures of time-resolved CV quadrature entanglement and intensity difference squeezing have been analyzed for periodically-pulsed optical parametric oscillator (OPO). An application to quantum key distribution scheme based on intensity correlation of twin beams has also been considered. The text was submitted by the author in English.