Quantum-dot Semiconductor Optical Amplifiers in State Space Model

A state space model(SSM) is derived for quantum-dot semiconductor optical amplifiers(QD-SOAs).Rate equations of QD-SOA are formulated in the form of state update equations,where average occupation probabilities along QD-SOA cavity are considered as state variables of the system.Simulations show that SSM calculates QD-SOA′s static and dynamic characteristics with high accuracy.

An Electroabsorption Modulator Monolithically Integrated with a Semiconductor Optical Amplifier and a Dual-Waveguide Spot-Size Converter

A semiconductor optical amplifier and electroabsorption modulator monolithically integrated with a spotsize converter input and output is fabricated by means of selective area growth,quantum well intermixing,and asymmetric twin waveguide technology. A 1550-1600nm lossless operation with a high DC extinction ratio of 25dB and more than 10GHz 3dB bandwidth are successfully achieved. The output beam divergence angles of the device in the horizontal and vertical directions are as small as 7.3°× 18.0°, respectively, resulting in a 3.0dB coupling loss with a cleaved single-mode optical fiber.

An autobias control system for the electro optic modulator used in a quantum key distribution system

In a quantum key distribution system, it is crucial to keep the extinction ratio of the coherent pulses stable. This means that the direct current bias point of the electro-optic modulator （EOM） used for generating coherent pulses must be locked. In this paper, an autobias control system based on a lock-in-amplifier for the EOM is introduced. Its drift information extracting theory and control method are analyzed comprehensively. The long term drift of the extinction ratio of the coherent pulses is measured by a single photon detector, which indicates that the autobias control system is effective for stabilizing the bias point of the EOM.

Perfect photon absorption based on the optical parametric process

The perfect photon absorption is studied in a cavity quantum electrodynamics(CQED) system, in which an optical parameter amplifier(OPA) is coupled to the cavity mode. This makes it possible to control the optical phase to realize the perfect photon absorption. It is found that in the presence of one and two injected fields, the perfect photon absorption is present in these two cases and can be controlled by adjusting the parametric phase. Moreover, different from the previous predictions of perfect photon absorption in atomic CQED systems, the perfect photon absorption can be changed significantly by the relative phase. Our work provides a new platform to use the parametric processes to make an available way to control the behaviors of photons and to take advantage of the optical phase to achieve the perfect photon absorption.

Improving Continuous-Variable Measurement-Device-Independent Multipartite Quantum Communication with Optical Amplifiers

The developing tendency of continuous-variable （CV） measurement-device-independent （MDI） quantum cryptography is to cope with the practical issue of implementing sealable quantum networks. Up to now, most theoretical and experimental researches on CV-MDI QKD are focused on two-party protocols. However, we suggest a CV-MDI multipartite quantum secret sharing （QSS） protocol use the EPR states coupled with optical amplifiers. More remarkable, QSS is the real application in multipartite CV-MDI QKD, in other words, is the concrete implementation method of multipartite CV-MDI QKD. It can implement a practical quantum network scheme, under which the legal participants create the secret correlations by using EPR states connecting to an untrusted relay via insecure links and applying the multi-entangled Greenberger-Horne-Zeilinger （GHZ） state analysis at relay station. Even if there is a possibility that the relay may be completely tampered, the legal participants are still able to extract a secret key from network communication. The numerical simulation indicates that the quantum network communication can be achieved in an asymmetric scenario, fulfilling the demands of a practical quantum network. Additionally, we illustrate that the use of optical amplifiers can compensate the partial inherent imperfections of detectors and increase the transmission distance of the CV-MDI quantum system.

Nonlinear properties of quantum dot semiconductor optical amplifiers at 1.3 μm:errata

The authors regret that one of the coauthors was inadvertently omitted in the previous paper. E. Varene was a member of the Institut fur Festk6rperphysik at the Technische Universitat Berlin and contributed to the results on cross-phase modulation.

Emerging near-infrared luminescent materials fornext-generation broadband optical communications

The rapid development of emerging technologies observed in recent years,such as artificial intelligence, machine learning, mobile internet, big data,cloud computing, and the Internet of Everything, are generating escalatingdemands for expanding the capacity density, and speed in next-generation opticalcommunications. This poses a significant challenge to existing communicationtechniques. Within this context, the integration of near-infraredbroadband, tunable, and high-gain luminescent materials into silicon opticalcircuits or fiber architectures to transmit and modulate light shows enormouspotential for advancing next-generation communication techniques. Here, thisreview provides an overview of the recent breakthroughs in near-infrared luminescentepitaxial/colloidal quantum dots, and metal-active-center-doped materialsfor broadband optical amplifiers and tunable lasers. We also expound onefforts to enhance the bandwidth and gain of these materials-based amplifiersand lasers, exploring the challenges associate with developing ultra-broadbandand high-speed optical communication systems. Additionally, the potentialapplications in Fifth Generation Fixed Networks, integration with 5G and 6Gwireless networks, compensation for current Si electronic based CMOS forhigh computing capability, and the prospects of these light sources for nextgenerationoptoelectronic devices are discussed.

Calculation of Valence Subband Structures for Strained Quantum-Wells by Plane Wave Expansion Method Within 6×6 Luttinger-Kohn Model

The valence subband energies and wave functions of a tensile strained quantum well are calculated by the plane wave expansion method within the 6×6 Luttinger Kohn model.The effect of the number and period of plane waves used for expansion on the stability of energy eigenvalues is examined.For practical calculation,it should choose the period large sufficiently to ensure the envelope functions vanish at the boundary and the number of plane waves large enough to ensure the energy eigenvalues keep unchanged within a prescribed range.

调制光学参量放大器对双机械振子量子纠缠与压缩的影响

为了研究包含调制光参量放大器(optical parametric amplifier,OPA)的双机械振子腔光力系统中的量子纠缠和机械压缩,通过数值求解和解析求解,讨论了系统的有关参数,如OPA相位、调制频率、热声子数和相位增益量在腔光力系统中对量子纠缠和机械压缩的影响,重点分析了调制OPA对产生力学纠缠和机械压缩的作用.结果表明:本光学腔不需要额外的压缩光来驱动,并在较易实现的参数条件下通过调制OPA增强了2个机械振子间的纠缠.当系统处于稳定状态时,在边带可分辩和不可分辨条件下均可产生机械压缩,并可通过调制OPA在边带可分辨条件下实现强机械压缩.此外,在调制OPA的辅助下,机械振子间的纠缠和机械压缩对环境温度具有很强的鲁棒性.

Broadrange tunable slow and fast light in quantum dot photonic crystal structure

Slow and fast light processes, based on both structural and material dispersions, are realized in a wide tuning range in this article. Coherent population oscillations （CPO） in electrically tunable quantum dot semiconductor optical amplifiers lead to a variable group index ranging from the background index （nbgd） to^30. A photonic crystal waveguide is then dispersion engineered and a group index of 260 with the normalized delay-bandwidth product （NDBP） of 0.65 is achieved in the proposed waveguide. Using comprehensive numerical simulations, we show that a considerable enhancement of slow light effect can be achieved by combining both the material and the structural dispersions in the proposed active QDPCW structure. We compare our developed FDTD results with analytical results and show that there is good agreement between the results, which demonstrates that the proposed electrically-tunable slow light idea is obtainable in the QDPCW structure. We achieve a total group index in a wide tuning range from nbgd to^1500 at the operation bandwidth, which shows a significant enhancement compared with the schemes based only on material or structural dispersions. The tuning range and also NDBP of the slow light scheme are much larger than those of the electrically tunable CPO process.

40 Gb/s NRZ-DQPSK data wavelength conversion with amplitude regeneration using four-wave mixing in a quantum dash semiconductor optical amplifier

Differential quadrature phase shift keying （DQPSK） modulation is attractive in high-speed optical communications because of its resistance to fiber non-linearities and more efficient use of fiber bandwidth compared to conventional intensity modulation schemes. Because of its wavelength conversion ability and phase preservation, semiconductor optical amplifier （SOA） four- wave mixing （FWM） has attracted much attention. We experimentally study wavelength conversion of 40 Gbit/s （20 Gbaud） non-return-to-zero （NRZ）-DQPSK data using FWM in a quantum dash SOA with 20 dB gain and 5 dBm output saturation power. Q factor improvement and eye diagram reshaping is shown for up to 3 nm pump-probe detuning and is superior to that reported for a higher gain bulk SOA.

PbS量子点掺杂聚合物宽带光纤放大器

随着人工智能、大数据、云计算、物联网、移动电子等的发展,传统的稀土离子掺杂单芯单模光纤放大器承载的光纤通信系统的传输容量已经逐渐接近香农极限,需要发展新型材料体系,以拓宽光纤通信系统的传输容量。相比于稀土离子,量子点具有较宽的发光带宽、可调波长的发光特性,且量子点的发光性质可以通过多种化学手段调控,在量子点光放大器上显示出了宽带光放大特性,受到学术界和产业界的广泛关注。在该背景下,本文提出将化学合成的PbS/CdS核壳量子点与低损耗聚合物集成,获得量子点掺杂光纤放大器,实现近红外通信波段可调波长、宽带光放大特性。文章研究并揭示了影响固化后的聚合物纤芯连续性的因素和影响机制,提出了降低固化胶前驱体液面附加压力、固化收缩力、聚合物前驱体与光纤内壁的摩擦力,并提高抽真空产生的牵引力以获得连续光纤,在此基础上获得了基于热固化聚二甲基硅氧烷(PDMS)和光固化NOA61、NOA85固化胶的纤芯连续光纤,量子点光纤在1530~1630 nm获得了增益带宽达到100 nm以上的开关增益,最高增益达到6.5 dB。本文的研究结果将促进量子点光纤器件和宽带光通信技术的发展。

基于不可信纠缠源的高斯调制连续变量量子密钥分发

在实际的量子通信系统中,连续变量量子密钥分发的信源安全可能会因为器件的缺陷或隐藏的攻击而受到威胁.针对这个问题,本文提出了基于不可信纠缠源的高斯调制连续变量量子密钥分发方案,通过将高斯纠缠源置于不可信的量子信道来模拟纠缠源被攻击者所控制的场景,从而验证实际复杂环境下高斯调制连续变量量子密钥分发的安全性.本文详细分析不可信纠缠源对系统安全性的影响并引入了两种光学放大器来辅助提升所提方案的实际性能.仿真实验结果表明,本文所提方案即使在高斯纠缠源不可信的情况下仍然能够产生安全的量子密钥,同时,光学放大器也能够有效提升接收端探测器的量子效率.该工作旨在推动高斯调制连续变量量子密钥分发系统的实用化进程,为高斯调制连续变量量子密钥分发系统的实际部署和应用提供理论指导.

Enhancing force sensing in a squeezed optomechanical system with quantum nondemolition measurement

A theoretical scheme is proposed to enhance the sensitivity of force sensors with quantum nondemolition measurement(QND)in an optomechanical setup assisted by four-tone optical driving and an optical parametric amplifier(OPA).With the help of special drive,the system can be simplified as the typical type of QND for force sensing,so that the backaction noise can be evaded to surpass the standard quantum limit.Besides,the added noise can be suppressed owing to the modified optical susceptibility resulting from the OPA.By introducing two oscillators coupling with two charged bodies respectively,the signal can be enhanced with the nonlinearity caused by Coulomb interaction,while the noise presents an exponential decrease.Moreover,considering the homodyne detection effect,the range of system parameters and frequency bands will be broadened.The present investigation may provide a route toward simultaneously evading backaction noise,reducing the mechanical thermal noise,and enhancing the external signal,which can be an alternative design for sensitive devices.

特种光纤及器件研究

特种光纤及器件在光纤通信、光纤传感、光纤激光等领域有非常广泛的应用.近年来,上海大学特种光纤与光接入网省部共建重点实验室将纳米技术与特种光纤及器件相结合,开展了特种纳米半导体掺杂光纤、抗辐射光纤、包层模谐振光纤以及量子点光纤放大器等方面的研究,并探索了它们在宽光谱光放大、特种光纤传感器等方面的应用.

连续变量纠缠态光场在光纤中传输特性的实验研究

连续变量纠缠态由于其确定性产生、高效率的特点而被广泛应用于连续变量量子信息处理.在量子信息处理过程中纠缠态与量子信道发生相互作用而退相干,这是限制长距离量子信息发展的重要因素之一.光纤信道作为理想的量子信道,是目前连续变量量子信息研究关注的热点.本文利用Ⅱ类匹配的楔角极化磷酸氧钛钾晶体构成了三共振的非简并光学参量放大器,获得了8.3 dB的光通信波段1.5μm连续变量纠缠态光场.将产生的纠缠态光场注入单模光纤,其量子特性在传输距离达50 km后仍得到保持,纠缠度为0.21dB.该研究可为基于光纤的长距离连续变量量子信息研究提供有效的依据.

高增益散粒噪声探测器的性能改进

针对量子光学实验对低噪声探测器的特殊需求,采用交流电流耦合跨阻抗前置放大电路和ETX500光电二极管设计了高增益散粒噪声探测器.与现有的探测器相比,该探测器在增益、带宽、交直流饱和特性3方面的性能均有明显提升.采用1 064 nm的单频激光器作光源,频谱分析仪作噪声测量工具,测量了探测器的输出特性.在分析频率2 MHz处,测量得到注入探测器的功率为850 μW时,输出的噪声功率谱较电子学噪声谱高10 dB;注入探测器的功率大于1.62mW时,探测器的带宽达到5 MHz.注入的光功率为0.85～36 mW时,探测器保持良好的交流与直流线性特性.设计的探测器的高增益与较高的交直流饱和特性,为量子光学实验提供了重要的探测工具.

QD-SOA的四波混频及DPSK信号的异或逻辑研究

采用有限差分方法对量子点半导体光放大器(QD-SOA)中的四波混频(FWM)现象进行了研究。通过仿真计算,分析了多个参数对四波混频效率的影响。增强泵浦光功率、增大QD-SOA的长度以及注入电流,四波混频效率明显增大。增大探测光功率以及泵浦光和探测光的波长间隔,四波混频效率均降低。基于四波混频效应实现了差分相移键控信号的异或逻辑操作,模拟得到了异或逻辑的时域和频域输出结果。在多个波长位置同时实现了异或逻辑,并对32比特的序列异或操作进行了仿真研究,得到了异或逻辑的时序结果及眼图。

优化抽运空间分布实现连续变量超纠缠的纠缠增强

超纠缠近年来受到人们广泛的关注,其在量子信息和量子通信领域具有非常重要的作用.在Liu等(2014 Phys. Rev. Lett. 113 170501)的工作中,他们利用二类相位匹配的非简并光学参量放大器获得了约1.00 dB的同时具有轨道角动量和自旋角动量纠缠的连续变量超纠缠态.在此基础上,本文通过进一步分析抽运模式与下转换模式间的纠缠关系,优化了抽运空间构造.实验结果表明,相比Liu等利用高斯基模做抽运场,使用优化的抽运模式时轨道角动量纠缠和自旋角动量纠缠的不可分度分别提高了96.2%和96.3%,最终将超纠缠态的纠缠度提高到了(4.00±0.02) dB,为连续变量超纠缠态的进一步应用奠定了基础.

基于非简并光学参量放大器产生光学频率梳纠缠态

实验研究了阈值以下非简并光学参量放大器中的频率梳纠缠特性,在实验上制备了具有频率梳结构的Einstein-Podolsky-Rosen纠缠,实验中对5对频率梳边带间纠缠进行了测量,纠缠度约为4.5 dB.该频率梳纠缠态作为一种可扩展的量子信息系统,可为实现频分复用的多通道离物传态的实验提供必要的光源,为未来大容量的量子通信与网络提供了新思路.