二维光量子阱共振隧穿光谱特性的改善

用时域有限差分法研究了光子晶体量子阱中的量子化能态.研究发现,开腔与闭腔光量子阱结构共振透射峰的数目相同,位置几乎不变,但闭腔光量子阱出射光强更强,透射率更大,频率选择性更好,品质因子Q值更高.同时计算了开腔和闭腔光量子阱光场分布,结果表明,开腔光量子阱为行波阱,闭腔光量子阱为驻波阱,充分证实了闭腔光量子阱更能束缚光场的设想,对其作用机理进行了探讨.     

Quantum dots in photonic crystals: From quantum information processing to single photon nonlinear optics

Quantum dots in photonic crystals are interesting both as a testbed for fundamental cavity quantum electrodynamics (QED) experiments and as a platform for quantum and classical information processing. We describe a technique to coherently access the QD-cavity system by resonant light scattering. Among other things, the coherent access enables a giant optical nonlinearity associated with the saturation of a single quantum dot strongly coupled to a photonic crystal cavity. We explore this nonlinearity to implement controlled phase and amplitude modulation between two modes of light at the single photon level—a nonlinearity observed so far only in atomic physics systems. We also measured the photon statistics of the reflected beam at various detunings with the QD/cavity system. These measurements reveal effects such as photon blockade and photon-induced tunneling, for the first time in solid state. These demonstrations lie at the core of a number of proposals for quantum information processing, and could also be employed to build novel devices, such as optical switches controlled at the single photon level.     

Electro-absorption and refraction in Fabry-Perot quantum well modulators: a general discussion

Fabry-Perot resonators have long been advocated to improve the limited contrast ratio of multiple quantum well optical modulators used in photonic switches based on self electrooptic effect devices (SEEDs) and in other array based optical interconnection schemes. Using data on field dependent GaAs/AlGaAs quantum well absorption and refraction, we have modelled the reflectivity, modulation depth and contrast ratio of resonant modulators. Our results are generally valid for any quantum well modulator and demonstrate 23the important role played by electro-refraction even in regions of strong absorption. Resonators give large contrast ratios but there are trade-offs in the maximum reflectivity change achievable with Fabry-Perot resonators compared to simple modulators. The model gives the optimum number of quantum wells and reflectivity values required to make a resonator at any wavelength for a given quantum well structure. Understanding the limits of Fabry-Perot quantum well modulator performance is important for their application in symmetric self electrooptic effectiveness for photonic switching where modulation and detection properties are both used and for optical interconnection systems.     

GaAs integrated quantum photonics: Towards compact and multi‐functional quantum photonic integrated circuits

The recent progress in integrated quantum optics has set the stage for the development of an integrated platform for quantum information processing with photons, with potential applications in quantum simulation. Among the different material platforms being investigated, direct‐bandgap semiconductors and particularly gallium arsenide (GaAs) offer the widest range of functionalities, including single‐ and entangled‐photon generation by radiative recombination, low‐loss routing, electro‐optic modulation and single‐photon detection. This paper reviews the recent progress in the development of the key building blocks for GaAs quantum photonics and the perspectives for their full integration in a fully‐functional and densely integrated quantum photonic circuit.

     

光极限探测技术在空间通信中的应用

光是人类最早的科学研究对象之一,光子是光的最小能量单元,具备量子的基本特征.随着科学技术发展,人类已经能够实现对单个光子的极限探测.光的常规探测已经普遍应用于地面光纤通信中,而光的极限探测则在空间量子通信及深空超远距离光通信中具备重要的应用价值.文章介绍了光极限探测技术在空间量子科学实验、空间光子通信中的典型应用及涉及...     

On‐chip single photon sources using planar photonic crystals and single quantum dots

We review the basic light‐matter interactions and optical properties of chip‐based single photon sources, that are enabled by integrating single quantum dots with planar photonic crystals. A theoretical framework is presented that allows one to connect to a wide range of quantum light propagation effects in a physically intuitive and straightforward way. We focus on the important mechanisms of enhanced spontaneous emission, and efficient photon extraction, using all‐integrated photonic crystal components including waveguides, cavities, quantum dots and output couplers. The limitations, challenges, and exciting prospects of developing on‐chip quantum light sources using integrated photonic crystal structures are discussed.     

渐变折射率光量子阱对束缚态能级的调整

在对称的均匀电介质材料光子晶体体系中插入另一折射率渐变的光子晶体可构成光量子阱结构.利用时域有限差分法计算了不同折射率分布光量子阱结构的传输谱.研究表明：束缚态是对处于垒光子晶体禁带中的阱光子晶体导通带的离散化,束缚态能级个数等于阱光子晶体结构单元的重复周期数；以渐变方式调整阱区折射率分布,可在特定频率范围内得到新的互不交叠的束缚态.这样在有限的禁带区域可以成倍增加光子束缚态而无需增大光量子阱结构的尺寸,使信道密度最大化、光波有效带宽的使用最优化.这种量子阱结构可用于制作超窄带滤波器和多通道窄带滤波器,有望在光通信超密集波分复用和光学精密测量技术中获得广泛应用. 关键词： 光量子阱 光子束缚态 渐变折射率 光子晶体     

Atomic spectroscopy and quantum optics in hollow‐core waveguides

Atomic spectroscopy is a well‐established, integral part of the physicist's toolbox with an extremely broad range of applications ranging from astronomy to single atom quantum optics. While highly desirable, miniaturization of atomic spectroscopy techniques on the chip scale was hampered by the apparent incompatibility of conventional solid‐state integrated optics and gaseous media. Here, the state of the art of atomic spectroscopy in hollow‐core optical waveguides is reviewed The two main approaches to confining light in low index atomic vapors are described: hollow‐core photonic crystal fiber (HC‐PCF) and planar antiresonant reflecting optical waveguides (ARROWs). Waveguide design, fabrication, and characterization are reviewed along with the current performance as compact atomic spectroscopy devices. The article specifically focuses on the realization of quantum interference effects in alkali atoms which may enable radically new optical devices based on low‐level nonlinear interactions on the single photon level for frequency standards and quantum communication systems.     

Laser communication transmitter and receiver design

Free-space laser communication systems have the potential to provide flexible, high-speed connectivity suitable for long-haul intersatellite and deep-space links. For these applications, power-efficient transmitter and receiver designs are essential for cost-effective implementation. State-of-the-art designs can leverage many of the recent advances in optical communication technologies that have led to global wide-band fiber-optic networks with multiple Tbit/s capacities. While spectral efficiency has long been a key design parameter in the telecommunications industry, the many THz of excess channel bandwidth in the optical regime can be used to improve receiver sensitivities where photon efficiency is a design driver. Furthermore, the combination of excess bandwidth and average-power-limited optical transmitters has led to a new paradigm in transmitter and receiver design that can extend optimized performance of a single receiver to accommodate multiple data rates. This paper discusses state-of-the-art optical transmitter and receiver designs that are particularly well suited for average-power-limited photon-starved links where channel bandwidth is readily available. For comparison, relatively simple direct-detection systems used in short terrestrial or fiber optic links are discussed, but emphasis is placed on mature high-performance photon-efficient systems and commercially available technologies suitable for operation in space. The fundamental characteristics of optical sources, modulators, amplifiers, detectors, and associated noise sources are reviewed along with some of the unique properties that distinguish laser communication systems and components from their RF counterparts. Also addressed is the interplay between modulation format, transmitter waveform, and receiver design, as well as practical tradeoffs and implementation considerations that arise from using various technologies.     

基于光子晶体光纤中多抽运四波混频效应的新型光层组播技术

光层组播是未来透明光子网络中一项重要的全光信号处理功能,提出并实验证实了一种基于色散平坦高非线性光子晶体光纤中多抽运四波混频效应的光层组播方法,将一束信号光与两束连续抽运光同时输入高非线性光子晶体光纤中,通过多抽运四波混频过程,产生四个携带该数据信息的闲频光,从而实现了单一信号的四信道光层组播功能,组播信道波长在35.2 nm范围可调谐,组播信道最大间距4.4 THz,最大转换效率-22 dB,最优Q因子为5.3,该方法的特点在于基于光纤中的四波混频效应工作,因而具有对调制格式和比特率透明的 关键词： 光层组播 多抽运四波混频 光子晶体光纤     

基于光子晶体光纤中四波混频效应的单到双非归零到归零码型转换

归零(RZ)码与非归零(NRZ)码是波分复用和时分复用系统中广泛采用的两种码型, 全光NRZ到RZ码型转换能完成从波分复用到时分复用的网络接口功能, 是未来透明光子网络中一项重要的全光信号处理技术. 提出并实验证实了一种基于色散平坦高非线性光子晶体光纤中四波混频效应的单到双NRZ到RZ码型转换方法, 将一束信号光与同步时钟脉冲同时输入色散平坦高非线性光子晶体光纤中, 通过四波混频过程, 产生两个携带该数据信息的闲频光, 从而实现了单到双的NRZ到RZ码型转换功能, 码型转换器工作波长在193 nm范围可调谐, 最大转换效率为-21 dB, 最优消光比和品质因子分别为11.9 dB和7.2. 该方法的特点在于基于光纤中的四波混频效应工作, 因而具有对调制格式和比特率透明的优点, 同时, 光子晶体光纤特有的高非线与色散平坦性, 既避免了使用传统光纤需要较长的长度, 又避免了波长设置不灵活的弊端, 并具备可进一步增加带宽的能力, 且在码型转换的同时, 实现了波长转换, 完成了双通道波长组播功能. 整个系统为全光纤设计, 结构简单, 性能可靠, 并易于与现有的光纤通信系统相容, 对促进超高速大容量光子网络的发展具有重要意义. 关键词： 码型转换 四波混频 光子晶体光纤     

Quantum key distribution via fiber optic, fidelity and error corrections

We propose an interesting scheme on photon states generation using a fiber optic Mach Zehnder interferometer incorporating a fiber optic ring resonator without any optical pumping parts including in the system, which is available for long-distance link. In principle, the state of a quantum bit, it is known, unknown, or entangled to other systems. The desired quantum states are generated and transmitted in the link via a fiber optic. The transmission quality in terms of quantum fidelity is analyzed, where a high fidelity to the noiseless quantum channel is achieved by adding an ancillary photon after the signal photon within the correlation time of the fiber noise and by performing the quantum parity checking method. The error correction is also analyzed. For simplicity, feature and robustness against path-length mismatches among the nodes make our scheme suitable for multi-user quantum communication networks.     

A three‐level dark state and double‐control single‐photon logic gates via quantum coherent control

Multilevel quantum coherence and its quantum‐vacuum counterpart, where a three‐level dark state is involved, are suggested in order to achieve new photonic and quantum optical applications. It is shown that such a three‐level dark state in a four‐level tripod‐configuration atomic system consists of three lower levels, where constructive and destructive quantum interference between two control transitions (driven by two control fields) arises. We point out that the controllable optical response due to the double‐control tunable quantum interference can be utilized to design some fascinating new photonic devices such as logic gates, photonic transistors and switches at quantum level. A single‐photon two‐input XOR logic gate (in which the incident “gate” photons are the individual light quanta of the two control fields) based on such an effect of optical switching control with an EIT (electromagnetically induced transparency) microcavity is suggested as an illustrative example of the application of the dark‐state manipulation via the double‐control quantum interference. The present work would open up possibility of new applications in both fundamental physics (e.g., field quantization and relevant quantum optical effects in artificial systems that can mimic atomic energy levels) and applied physics (e.g., photonic devices such as integrated optical circuits at quantum level).     

Quantum photonic network on chip

We provide an overview of quantum photonic network on chip. We begin from the discussion of the pros and cons of several material platforms for engineering quantum photonic chips. Then we introduce and analyze the basic building blocks and functional units of quantum photonic integrated circuits. In the main part of this review, we focus on the generation and manipulation of quantum states of light on chip and are particularly interested in some applications of advanced integrated circuits with different functionalities for quantum information processing, including quantum communication, quantum computing, and quantum simulation. We emphasize that developing fully integrated quantum photonic chip which contains sources of quantum light, integrate circuits, modulators, quantum storage, and detectors are promising approaches for future quantum photonic technologies. Recent achievements in the large scale photonic chips for linear optical computing are also included. Finally, we illustrate the challenges toward high performance quantum information processing devices and conclude with promising perspectives in this field.     

Broadband 10 Gb/s operation of graphene electro‐absorption modulator on silicon

High performance integrated optical modulators are highly desired for future optical interconnects. The ultra‐high bandwidth and broadband operation potentially offered by graphene based electro‐absorption modulators has attracted a lot of attention in the photonics community recently. In this work, we theoretically evaluate the true potential of such modulators and illustrate this with experimental results for a silicon integrated graphene optical electro‐absorption modulator capable of broadband 10 Gb/s modulation speed. The measured results agree very well with theoretical predictions. A low insertion loss of 3.8 dB at 1580 nm and a low drive voltage of 2.5 V combined with broadband and athermal operation were obtained for a 50 μm‐length hybrid graphene‐Si device. The peak modulation efficiency of the device is 1.5 dB/V. This robust device is challenging best‐in‐class Si (Ge) modulators for future chip‐level optical interconnects.     

光纤中单光子传输方程的求解及分析

量子信息在光纤中传输时,会受到光纤损耗、色散、非线性效应等多因素的影响,将产生传输态的演化与能量转移.本文以单模光纤传输方程以及电磁场量子化理论为基础,对单模光纤中基模模场进行量子化处理,推导并建立了考虑损耗、色散、非线性效应后的单光子传输方程.基于微扰法对单光子非线性传输方程进行了求解,给出了稳定解存在的必要条件及其所满足的色散方程.深入讨论了广域光功率随微扰频率的变化关系,并且分析了光纤色散、非线性效应对解的影响.为量子光纤传输系统性能的深入研究奠定了理论基础.     

Implementations of quantum and classical gates with linear optical devices and photon number quantum non-demolition measurement for polarization encoded qubits

Aiming the construction of quantum computers and quantum communication systems based on optical devices, in this work we present possible implementations of quantum and classical CNOTs gates, as well an optical setup for generation and distribution of bipartite entangled states, using linear optical devices and photon number quantum non-demolition measurement.     

Error corrections of quantum key distribution of the quantum codes via optical wireless link

Quantum key generated by using a fiber optic Mach Zehnder interferometer incorporating a fiber optic ring resonator is proposed. The generated quantum key is distributed via an optical wireless link system, which is available for the free space link. The random quantum bits can be formed and used as the secret codes in quantum communication system. By adding an ancillary photon after the signal photon within the correlation time of the fiber noise and by performing quantum parity checking, the high fidelity to the noiseless quantum in free space is achieved by the technique known as the quantum error correction.     

Comb of high‐Q Resonances in a Compact Photonic Cavity

The optical equivalent of the quantum mechanical oscillator is demonstrated in a photonic crystal cavity, owing to the balance of the background dispersion and a bichromatic potential. Consequently, several equi‐spaced resonances with large loaded Q factors are obtained within a very tiny volume. A detailed statistical analysis is carried out by exploiting the complex reflection spectra measured with Optical Coherent Tomography. The log‐normal distribution of the intrinsic Q‐factors is centered at 0.7 million. The device is made of Ga_0.5In_0.5P in order to suppress the two photon absorption in the Telecom spectral range considered here. This is crucial to turn the strong localization of light into ultra‐efficient parametric interactions.