Transmissive 2-bit anisotropic coding metasurface

Coding metasurfaces have attracted tremendous interests due to unique capabilities of manipulating electromagnetic wave. However, archiving transmissive coding metasurface is still challenging. Here we propose a transmissive anisotropic coding metasurface that enables the independent control of two orthogonal polarizations. The polarization beam splitter and the orbital angular momentum (OAM) generator have been studied as typical applications of the anisotropic 2-bit coding metasurface. The simulated far field patterns illustrate that the x and y polarized electromagnetic waves are deflected into two different directions, respectively. The anisotropic coding metasurface has been experimentally verified to realize an OAM beam with l = 2 of right-handed polarized wave, resulting from both contributions from linear-to-circular polarization conversion and the phase profile modulation. This work is beneficial to enrich the polarization manipulation field and develop transmissive coding metasurfaces.     

All-optical quantization and coding scheme for ultrafast analog-to-digital conversion exploiting polarization switches based on nonlinear polarization rotation in semiconductor optical amplifiers

A novel all-optical quantization and coding scheme for ultrafast analog-to-digital (A/D) conversion exploiting polarization switches (PSWs) based on nonlinear polarization rotation (NPR) in semiconductor optical amplifiers (SOAs) is proposed. In addition, a theoretical model for the polarization switch based on NPR is presented. Through cascading two PSWs, a 2-period transfer function for 3-bit long all-optical quantization and coding is realized numerically for the first time to the authors’ knowledge. The effective number of bits (ENOB), the limitation of bandwidth and conversion speed and the scalability are also investigated. The proposed all-optical quantization and coding scheme, combined with existing all-optical sampling techniques, will enable ultrafast A/D conversion at operating speed of hundreds of Gs/s with at least 3 bit resolution, and allows low optical power requirements, photonic integration, and easy scalability.     

基于半波片的偏振跟踪理论分析

分析了卫星量子密钥分配中采用半波片进行偏振跟踪的原理，通过旋转半波片实现对偏振“零”方向的跟踪.针对BB84协议和B92协议，给出了三组共轭基六个光子偏振态的变换关系式，分析了基于偏振跟踪的量子密钥编码原理. 关键词： 量子密钥分配 偏振跟踪 半波片     

An ultra-wideband 2-bit coding metasurface using Pancharatnam—Berry phase for radar cross-section reduction

An ultra-wideband 2-bit coding metasurface is designed for radar cross-section (RCS) reduction. The design process is presented in detail, in which a polarization conversion metasurface (PCM) is first proposed. The proposed PCM can realize ultra-wideband circular polarization (CP) maintaining reflection. Moreover, Pancharatnam—Berry (PB) phase will be generated in the co-polarized reflection coefficient by rotating the metallic patches in its unit cells. Thus, based on the PCM, the four coding elements of a 2-bit coding metasurface are constructed using PB phase, and an ultra-wideband PB 2-bit coding metasurface is proposed according to an appropriate coding sequence. The simulated and experimental results show that the coding metasurface has obvious advantages of wideband and polarization-insensitivity. Compared to a metallic plate of the same size, it can achieve more than 10 dB RCS reduction in the frequency band from 9.8 GHz to 42.6 GHz with a relative bandwidth of 125.2% under normal incidence with arbitrary polarizations.     

矢量光束空间偏振编码的研究

矢量光束独特的空间偏振结构使之应用于空间偏振编码成为可能。提出了一种用一阶矢量光束的偏振分布进行极角空间编码的方法。通过矢量光束生成、光束偏振分布再调制实现了空间编码光束的生成,并采用斯托克斯参数法对空间编码光束进行检测。实验结果证实了一阶矢量光束应用于极角空间偏振编码的可行性,为基于空间偏振编码的激光驾束制导提供了新方法。     

基于相位调制偏振态QKD系统的量子信道校正发送方案

提出了一种基于相位调制偏振态QKD系统的量子信道校正发送的新方案—采用波导型相位调制器研制成电控连续可调光学相移器,它可随相位调制器输入电压的连续改变而产生连续的相移,从而控制输出的偏振态;在其前放置一个半波片,即可校正接收端偏振态量子态在信道中所发生的改变,从而保证信道传送密钥的可用性.通过理论推导和实验研究验证了基于相位调制偏振态QKD系统的量子信道校正发送方案的核心部件的可行性.由于本方案能实现高速调制（GHz）,为解决光纤传输的偏振编码QKD系统中偏振态漂移问题提供了一种新的途径.     

Analysis of polarization state in quantum key distribution via single-photon two-qubit states

An improved quantum key distribution scheme via single-photon two-qubit states is proposed. The input–output model of the polarization state is established. And the influence of the interferometers to the polarization state is analyzed. Quantum bit error rate of polarization coding caused by birefringent and coordinate system difference between incident light and the fast and slow axes in fiber interferometer is simulated. Furthermore, maintaining conditions of polarization state are given on this basis.     

Polarization state and image rotation via spontaneously generated coherence in a spinning fast light medium

In this article we propose a four-level rubidium (Rb⁸⁷ ) atomic system for observing interesting features of polarization state rotation in a fast light medium. We investigate spontaneously generated coherence (SGC) for a spinning medium. We show how SGC can affect different spectral profiles of the polarization state and images in this suggested model. We observe a 0.5 radian rotation and 2.5 microsecond time advancement in our proposed system. Our precise results will provide a new platform for researchers in quantum optics due to its applications in image coding, telecommunications and cloaking technology.     

Polarization optics of biphotons

The works devoted to studying the polarization properties of a two-photon light generated upon spontaneous parametric down-conversion in the collinear frequency-degenerate regime are briefly overviewed, with emphasis on the studies carried out by us over a period from 1999 to 2001 within the framework of the project “Polarization Optics of Biphotons” of the Russian Foundation for Basic Research. In particular, the polarization state of a two-photon light was analyzed and its pictorial mapping onto the Poincaré sphere was proposed. The experiments on polarization transformations of a two-photon light were performed; based on these transformations, a method was suggested for ternary quantum information coding. A two-photon state with the orthogonal photon polarizations was synthesized experimentally from the two beams of identically polarized correlated photons, and the spectral properties of this state were investigated. Finally, a method was suggested for measuring the polarization state of a two-photon light in the collinear frequency-degenerate case (“tomography”).     

Spatiotemporal polarization dynamics in a transverse multimode CO2 laser with optical feedback

We investigate the polarization dynamics in a quasi-isotropic CO₂ laser emitting on the TEM_01* mode subjected to an optical feedback. We observe a complex dynamics in which spatial mode and polarization competition are involved. The observed dynamics is well reproduced by a model that discriminates between the intrinsic asymmetry due to the kinetic coupling of molecules with different angular momenta and the anisotropy induced by the polarization feedback. We observe various dynamical regimes including chaotic dynamics and show that feedback changes these states from regular to chaotic and vice versa. Finally, the possible applications to polarization coding are discussed.     

Complete deterministic linear optics Bell state analysis

We show how hyperentanglement allows us to deterministically distinguish between all four polarization Bell states of two photons. In this proof-of-principle experiment, we employ the intrinsic time-energy correlation of photon pairs generated with high temporal definition in addition to the polarization entanglement obtained from parametric down-conversion. For the identification, no nonlinear optical elements or auxiliary photons are needed. The new possibilities this complete Bell measurement offers are demonstrated by realizing an optimal dense coding protocol.     

Optical computation based on nonlinear total reflectional optical switch at the interface

A new scheme of binary half adder and full adder is proposed. It realizes a kind of all-optical computation which is based on the polarization coding technique and the nonlinear total reflectional optical switches.      

Pattern-independent FSK heterodyne transmission with endless polarization control and a 119 photoelectrons/bit receiver sensitivity

We demonstrate 140-Mbit/s FSK transmission with a -56.7-dBm receiver sensitivity. The system features endless polarization control, Manchester coding to overcome the nonuniform FM response of the DFB laser, and a highly efficient sub-carrier demodulation scheme.     

Pattern-independent FSK heterodyne transmission with endless polarization control and a 119 photoelectrons/bit receiver sensitivity

We demonstrate 140-Mbit/s FSK transmission with a -56.7-dBm receiver sensitivity. The system features endless polarization control, Manchester coding to overcome the nonuniform FM response of the DFB laser, and a highly efficient sub-carrier demodulation scheme.     

Experimental demonstration of quantum source coding

We report an experimental demonstration of Schumacher's quantum noiseless coding theorem. Our experiment employs a sequence of single photons, each of which represents three qubits in terms of eight spatial and polarization modes. We initially prepare each photon in one of a set of eight nonorthogonal code word states corresponding to the value of a block of three binary letters. We use quantum coding to compress this quantum data into a two-qubit quantum channel and then uncompress the two-qubit channel to restore the original data with a fidelity approaching the theoretical limit.     

相位调制自由空间量子密钥分配

通过一组正对的望远镜耦合，采用以不等臂Mach-Zehnder干涉仪为基础的相位编码方式，成功地实现了实验室内12m距离的自由空间量子密钥分配. 实验表明这样的系统工作稳定可靠，与偏振编码一样，相位编码也可用于自由空间的量子密钥分配. 关键词： 不等臂Mach-Zehnder干涉仪 量子密钥     

QKD and QDC via optical-wireless link for quantum mobile telephone network application

We propose a novel system of the simultaneous continuous variable quantum key distribution (QKD) and quantum dense coding (QDC) using a soliton pulse within the nonlinear micro-ring resonator devices. By using the appropriate soliton input power and nonlinear micro-ring parameters, the continuous signals are generated spreading over the spectrum. The polarized photons are formed by using the polarization control unit incorporating into the micro-ring system, which is allowed the different time slot entangled photon pair randomly formed. Results obtained have shown that the application of such a system for the simultaneous continuous variable quantum cryptography and dense coding within a single system is plausible, which is can be implemented within the mobile telephone hand set and networks.     

电磁编码超材料的理论与应用

本文系统地对编码超材料、数字超材料及现场可编程超材料的新进展进行了综述,讨论其对电磁波的实时调控和构造多功能器件的能力。首先,引入1-bit编码超材料,由"0"和"1"两种编码单元构成,分别对应于相位相反的电磁响应。通过控制不同的"0"和"1"编码序列,可以调控电磁波,并实现不同功能。这种1-bit编码超材料可以扩展到2-bit,甚至更高比特。其次,介绍了一种由开关二极管来控制的数字编码超材料,每个编码单元可通过二极管的开和关来获得不同的相位响应,进而获得不同的数字态。结合现场可编程门阵列(FPGA)控制系统,实现了对数字超材料的实时可编程设计,构造出现场可编程超材料。最后,研究了编码超材料对太赫兹波的调控,包括太赫兹波宽带漫散射及其对目标雷达散射截面(RCS)的缩减、各向异性编码超材料对太赫兹波的极化调控和波束调控等。数值仿真和实验测试结果吻合很好,验证了编码超材料的出色性能,展示了编码超材料调控电磁波的多功能性。编码超材料对微波及太赫兹波的实时控制可用于制作波束分离、波束偏折、极化转换等功能器件,也可在宽带范围内有效缩减目标RCS。     

Systematic Encoding and Shortening of PAC Codes

Polarization adjusted convolutional (PAC) codes are a class of codes that combine channel polarization with convolutional coding. PAC codes are of interest for their high performance. This paper presents a systematic encoding and shortening method for PAC codes. Systematic encoding is important for lowering the bit-error rate (BER) of PAC codes. Shortening is important for adjusting the block length of PAC codes. It is shown that systematic encoding and shortening of PAC codes can be carried out in a unified framework.     

Optimization of a snapshot Mueller matrix polarimeter

We report on the optimization of a snapshot Mueller matrix polarimeter performed by using singular-value decomposition. The snapshot technique relies on wavelength polarization coding by four wave plates. The statistical noise on Mueller components is minimized through adjustment of the thickness of each plate. The spectrometer response and its cutoff frequency were considered to find the optimal configurations described here.