光子晶体环形谐振腔异质结构超微多路光分束器

基于直波导和环形谐振腔的耦合特性,设计了一种新型、高效的二维光子晶体异质结构光分束器.时域有限差分法模拟表明,该设计仅仅通过改变介质柱的折射率,使光场发生重新分布,便可实现输出能量的均分或自由分配.在通信波长范围,该设计结构尺寸小、分束角度大、分束率高,这些特性使其在光通信领域具有重要的应用前景.     

Two-dimensional higher-diffraction-order optical beam splitter based on phenanthrenequinone-doped poly(methyl methacrylate) photopolymer

A two-dimensional optical beam splitter has been realized that uses the higher diffraction orders of a refractive-index grating. Gratings were recorded experimentally with light from a semiconductor laser incident at a small angle on phenanthrenequinone-doped poly(methyl methacrylate) photopolymer. The incident signal beam, which was made up of three different wavelengths (632.8, 532.0, and 488.0 nm), was split by the grating into multiple output beams with nearly equal size and separation. Results are given for when the sample grating was placed behind, in front of, and in the focal plane of a Fourier lens. The properties of higher-order-diffraction images have been discussed. The discussion shows that a two-dimensional higher-diffraction-order optical beam splitter provides a practical method for splitting a signal beam.     

基于1×4光子晶体波导分束器的特性研究

光子晶体波导分束器是集成光学电路的重要组成元件。设计一种线缺陷1×4光子晶体分束器,用时域有限差分法研究其特性。实验结果表明:输出端的透射传输特性随入射光的波长和分支的几何形状有关,并且入射波分别相等地流入4个输出端口。为了减少1×4分束器在3个Y型分支区的反射,通过调节分支区的可调介质柱的半径R,可使每个输出端口输出较高的透射率。     

纠缠压缩真空态的纠缠转移

通过分析光学分束器对压缩真空态光场的作用,发现如果分束器的输入光是两束具有同样振幅和相位的单模压缩真空态光场,则输出光为双模压缩真空态光场;若分束器的输入光是两束具有同样振幅但有π相位差的单模压缩真空态光场,则输出光仍为两束单模压缩真空态光场.对于双模压缩真空态光场,每个模中容纳的光子数可以是基数或偶数.而对于单模压缩真空态光场,每个模中只能包含偶数个光子.根据这些结果,提出了一个纠缠转移的方案.在这个方案中,两个纠缠压缩真空态光场被用作量子信道,通过利用光学分束器作用和光子数探测的方法,并在经典通讯的帮助下,实现了三个通讯伙伴之间的纠缠转移.     

Second-order temporal interference of two independent light beams at an asymmetrical beam splitter

The second-order temporal interference of classical and nonclassical light at an asymmetrical beam splitter is discussed based on two-photon interference in Feynman's path integral theory. The visibility of the second-order interference pattern is determined by the properties of the superposed light beams, the ratio between the intensities of these two light beams, and the reflectivity of the asymmetrical beam splitter. Some requirements about the asymmetrical beam splitter have to be satisfied in order to ensure that the visibility of the second-order interference pattern of nonclassical light beams exceeds the classical limit. The visibility of the second-order interference pattern of photons emitted by two independent single-photon sources is independent of the ratio between the intensities. These conclusions are important for the researches and applications in quantum optics and quantum information when an asymmetrical beam splitter is employed.     

Entanglement and photon statistics of output fields from beam splitter for binomial state inputs

The entanglement properties are investigated based on linear entropy, and nonclassicalities are examined of output fields from a beam splitter for pure binomial state inputs. It is shown that the properties of the entanglement and the photon statistics of output fields are not only strongly dependent on the parameters of input binomial states but also quite involved with the nature of the beam splitter. The best entanglement can be obtained when the parameters of both input states and the beam splitter are chosen appropriately. Finally, we analyse briefly the distinguishability between the joint input state and the joint output state.     

Dispersion-based beam splitter in photonic crystals

A novel implementation of a dispersion-based beam splitter in a photonic crystal (PhC) is proposed. The beam splitter consists of two periodic structures: a nonchannel dispersion-guiding region and a splitting structure operating inside the photonic bandgap. The dispersion-guiding PhC structure is used to route the optical wave by exploiting the dispersion properties of the lattice. An arbitrary power ratio between the output beams can be achieved by varying the parameters of the splitting structure. Within the studied range of splitting structures, high output power was observed and verified experimentally.     

Photon number distributions of output fields from a beam splitter

We examined the photon statistics of the output light field of a lossless symmetric beam splitter when a n-photon occupation number state and an arbitrary light field are present on the two input ports of the beam splitter. We showed that both the wave-like nature and the particle-like nature of light are contributed to the photon number distribution by investigation of the difference photon number probability at the output port.     

一种新型的光子晶体偏振光分束器的设计

基于光波在直波导和复合结构光子晶体中的传播特性,结合平面波展开法和时域有限差分法,提出并讨论了一种新型的超紧凑的光子晶体偏振光分束器. 它是由输入波导,分束结构和输出波导三部分组成. 对这种结构的三角晶格光子晶体光分束器的数值计算与模拟结果表明,该结构可以实现TE模和TM模的高效大角度分离,并且在通信波段设计尺寸小,这些特性使其在未来的集成光回路中有着重要的应用前景. 关键词： 偏振光分束器 能带结构 平面波展开法 时域有限差分法     

Photonic crystal beam splitters

In this work, the beam splitter with two input ports and two output ports in two-dimensional photonic crystals is studied through the finite-difference time-domain method. The beam splitter consists of two orthogonally cross line defects. The diameter of the two diagonal air holes at the intersection of the two line defects was modified. The input light can be identically divided into the two output ports. The beam splitters can be applied in the photonic crystal Mach-Zehnder interferometers or photonic crystal optical switches.     

Ultracompact high-efficiency polarizing beam splitter with a hybrid photonic crystal and conventional waveguide structure

We propose an ultracompact high-efficiency polarizing beam splitter that operates over a wide wavelength range and is based on a hybrid photonic crystal and a conventional waveguide structure. Within a small area (15 microm x 10 microm), this polarizing beam splitter separates TM- and TE-polarized modes into orthogonal output waveguides. Results of simulations with the two-dimensional finite-difference time-domain method show that 99.3% of TM-polarized light is deflected by the photonic crystal structure (with a 28.0-dB extinction ratio), whereas 99.0% of TE-polarized light propagates through the structure (with a 32.2-dB extinction ratio). Wave vector diagrams are employed to explain the operation of a polarizing beam splitter. Tolerance analysis reveals a large tolerance to fabrication errors.     

Entanglement Properties of Output Field from Beam Splitter with the Generalized Two-Mode Squeezed Vacuum State Inputs

Entangling properties of output field from beam splitter are investigated with the generalized two-mode squeezed vacuum state inputs. It is found that the entanglement are not only strongly dependent on the squeezing parameters of the input state but also quite involved with the angular parameter of the beam splitter. By appropriately choosing the parameters of both input field and the beam splitter, the best entanglement can be obtained.     

Engineering Two-Mode Non-Gaussian States with Vortex Structures Using a Beam Splitter

Vortex structure and entanglement properties of output field from a beam splitter are investigated. With a n-photon Fock state and a coherent state as the inputs, it is found that the output state before a beam splitter bears a vortex structure in quadrature space and is always entangled and non-classical based on the linear entropy criterion and the P-function analysis in phase space.     

Coupled metallic ring gap waveguide

Employing the surface plasmon polaritons (SPPs), a kind of coupled metallic squareness ring waveguide structure is presented. Its properties has been analyzed with the finite different time domain method and the coupling length has been derived from the coupled mode theory. It is demonstrated that the SPPs excited by the light with different wavelength will come out from different output port due to different coupling length. By appropriately designing the structure, it can be utilized to realize some optics devices such as multiple-wavelength sorter and beam splitter. This will break through the diffraction limit of traditional optical devices.     

高能激光束自动对准和稳定系统的结构设计

介绍了一种用于两个光学平台之间光轴自动对准和稳定光束的设计方案。以可绕ｘ,ｙ,ｚ三个方向转动的导光管为单元,组成导光臂连接两个光学平台,消除两个平台之间相对运动产生的光轴对接偏差。用压电陶瓷驱动的倾斜镜作光束稳定元件,消除光束自身的漂移和平台间高频振动产生的光轴偏差。     

法拉第镜旋转角的偏振分束测量法

提出了基于偏振分束法的法拉第镜偏振旋转角的测量方法.利用非偏振分束器改变法拉第镜出射光的方向,偏振分束器将该出射光分为p光和s光,分别测量其光强,应用后续"差除和"信号处理方案消除光源波动的影响,推导出法拉第镜偏振旋转角的理论表达式.分析了起偏器的消光比非0及起偏角误差对输出结果的影响,分别是0.057 29°和-0.100 0°.实验验证了该方法的可行性,重复测量结果为89.68°,均方值为0.014 93.     

Polarization beam splitter with wide bandwidth in air-hole-based periodic dielectric waveguides

A polarization beam splitter with wide bandwidth and simple structure in air-hole-based periodic dielectric waveguides has been proposed and designed. Operation principle of the device is based on different directional coupling properties of beams in TE and TM polarizations in parallel periodic dielectric waveguides. Performances have been evaluated by a finite-difference time-domain simulation. Results show that the polarization beam splitter provides a wide bandwidth of 113 nm with both a high extinction ratio (higher than 21 dB) and a low insertion loss (less than 1.5 dB) for optical communication wavelengths at ∼1.55 μm. Moreover, the performances of the polarization beam splitter are insensitive to longitudinal alignment errors in the coupling region, which is desirable for device fabrication and practical application.     

Higher diffraction order photorefractive optical beam splitter

A higher diffraction order photorefractive (PR) optical beam splitter has been realized based on a PR higher diffraction order grating. In the experiments, the beam splitter was produced by two-wave coupling at a small incident angle in Fe:LiNbO₃ using the output from a He–Ne laser at 632.8 nm. An incident signal beam containing three different wavelengths (632.8, 532.0 and 488.0 nm) was split into multi-output beams by the beam splitter. The size of higher diffraction order is given and the influence of crystal thickness is discussed. Results show that the higher diffraction order PR optical beam splitter provides a practical method to split a multi-wavelength signal beam.     

利用分束器通过条件测量制备非经典光场态和量子纠缠态

把相干态和单粒子数态作为分束器的输入态，通过条件测量可以剪去输入相干态中的任意粒子数态，并研究了这些被剪切了的光场态的性质。结果显示剪去真空态和单粒子数态的输出态具有较强的压缩和亚泊松分布等非经典效应。把剪切了的输出态和真空态输入分束器，得到的输出态具有量子纠缠性质，从而制备出量子纠缠态，同时也验证了被剪切的输出态的非经典性。     

Slow light beam splitter

We demonstrate a slow light beam splitter using rapid coherence transport in a wall-coated atomic vapor cell. We show that particles undergoing random and undirected classical motion can mediate coherent interactions between two or more optical modes. Coherence, written into atoms via electromagnetically induced transparency using an input optical signal at one transverse position, spreads out via ballistic atomic motion, is preserved by an antirelaxation wall coating, and is then retrieved in outgoing slow light signals in both the input channel and a spatially-separated second channel. The splitting ratio between the two output channels can be tuned by adjusting the laser power. The slow light beam splitter may improve quantum repeater performance and be useful as an all-optical dynamically reconfigurable router.