Dynamic Thermal Emission Control Based on Ultrathin Plasmonic Metamaterials Including Phase‐Changing Material GST

Dynamic thermal emission control has attracted growing interest in a broad range of fields, including radiative cooling, thermophotovoltaics and adaptive camouflage. Previous demonstrations of dynamic thermal emission control present disadvantages of either large thickness or requiring sustained electrical or thermal excitations. In this paper, an ultrathin (∼0.023λ, λ is the emission peak wavelength) metal‐insulator‐metal plasmonic metamaterial‐based zero‐static‐power mid‐infrared thermal emitter incorporating phase‐changing material GST is experimentally demonstrated to dynamically control the thermal emission. The electromagnetic modes can be continuously tuned through the intermediate phases determined by controlling the temperature. A typical resonance mode, which involves the coupling between the high‐order magnetic resonance and anti‐reflection resonance, shifts from 6.51 to 9.33 μm while GST is tuned from amorphous to crystalline phase. This demonstration will pave the way towards the dynamical thermal emission control in both the fundamental science field and a number of energy‐harvesting applications.     

High-Speed Quantum Transducer with a Single-Photon Emitter in a 2D Resonator

Quantum transducers can transfer quantum information between different systems. Microwave–optical photon conversion is important for future quantum networks to interconnect remote superconducting quantum computers with optical fibers. Here, a high-speed quantum transducer based on a single-photon emitter in an atomically thin membrane resonator, that can couple single microwave photons to single optical photons, is proposed. The 2D resonator is a freestanding van der Waals heterostructure (which may consist of hexagonal boron nitride, graphene, or other 2D materials) that hosts a quantum emitter. The mechanical vibration (phonon) of the 2D resonator interacts with optical photons by shifting the optical transition frequency of the single-photon emitter with strain or the Stark effect. The mechanical vibration couples to microwave photons by shifting the resonant frequency of an LC circuit that includes the membrane. Thanks to the small mass of the 2D resonator, both the single-photon optomechanical coupling strength and the electromechanical coupling strength can reach the strong coupling regime. This provides a way for high-speed quantum state transfer between a microwave photon, a phonon, and an optical photon.     

基于马赫-曾德尔干涉仪的单个光子操控

分别利用空间和光纤马赫—曾德尔干涉仪对空间和光纤传输中的单个光子的干涉现象进行了研究,干涉对比度可达到90％以上,实现了空间和光纤中的单个光子的路由操控。实验采用脉冲调制加衰减的方法产生单个光子,获得了每个脉冲中只包含0．1个光子的准单光子源。通过改变压电换能器的电压控制马赫—曾德尔干涉仪的单个光子在两个输出端的选择,实现了光子在节点上的路由。采用同步符合检测技术,利用重复频率为1kHz,脉冲宽度为100ns的同步信号对输出信号进行符合,实现了量子效率高于70％,暗计数小于0．2s^-1的单光子高灵敏度检测,观测到了单个光子在相位操控下出射到两个输出端的有序分配现象。验证了基于马赫—曾德尔干涉仪的单个光子路由操控实现的可能性。     

Theory of coherent,degenerate two-photon absorption and emission

The theory of the coherent, two-photon resonant interaction of a monochromatic field with N atoms is given. It is seen that the dynamics of the atom-field system can be completely determined when the field is “strong”. Two specific examples are given: (i) two-photon absorption by atoms in ground state, and (ii) stimulated two-photon emission by fully excited atoms, assuming a coherent field in both cases. In case (ii), the field shows photon-antibunching after the decay of half of the atoms. The merits of our approach are shown by comparing with other treatments. Our results can also be applied to certain degenerate four-wave mixing processes which are described by a similar Hamiltonian.     

Single photon sources with single semiconductor quantum dots

In t.his contribution, we briefly recall the basic concepts of quantum optics and properties of semicon- ductor quantum clot. （QD） which a.re necessary to the nnderstanding of the physics of single-photon generation with single QDs. Firstly, we address the theory of quantmn emitter-cavity system, the fluorescence and optical properties of semiconductor QDs, and the photon statistics as well as opti- cal properties of the QDs. We then review the localizatioll of single semiconductor QDs in quantum confined optical microcavity systems to achieve their overall optical properties and perfornances in terms of strong coupling regime, elfieiency, directionality, and polarization control. Furthermore, we will discuss the recenl, progress on the fabrication of single photon sources, and various a.pproaehes for embedding single QDs into mieroca,vities or photonic crystal nanoeavities and show how to ex- tend the wavelength range. We focus in part;icular on new generations of electrically driven QD single photon source leading to high repetition rates, efficiencies at elevated temperature operation. Besides strong eoupling regime, and high collection new development;s of room temperature sin- gle photon emission in the strong coupling regime are reviewed. The generation of indistinguishable photons and remaining challenges for pract ical single-photon sources are also discussed.     

脉冲激光沉积方法制备ZnO薄膜生长参量对发光特性的影响

用脉冲激光沉积（PLD）方法在Si（111）衬底上制备了ZnO薄膜。以325nmHe-Cd激光器为光源对薄膜进行了荧光光谱分析,用X射线衍射仪（XRD）和原子力显微镜（AFM）分别对薄膜的结构和形貌进行了分析。脉冲激光沉积方法的主要生长参量为氧压、激光重复频率、生长温度和激光能量。通过控制这些参量变量,研究了这些参量对ZnO薄膜发光特性的影响,得到了用于紫外发光的ZnO薄膜生长的优化条件：发现在温度为650℃左右、氧压50Pa左右、频率5Hz左右的范围内能得到半峰全宽较窄,强度较大的紫外发光峰。分析认为紫外峰主要是由激子辐射复合发光形成的,绿光带主要和Ozn的存在密切相关,氧空位是蓝光发射的重要原因。     

Efficient Excitation of a Symmetric Collective Atomic State with a Single-Photon Through Dipole Blockade

In the famous quantum communication scheme developed by Duan et al.[L.M.Duan,M.D.Lukin,J.I.Cirac,and P.Zoller,Nature(London) 414(2001) 413],the probability of successful generating a symmetric collective atomic state with a single-photon emitted have to be far smaller than 1 to obtain an acceptable entangled state.Based on strong dipole-dipole interaction between two Rydberg atoms,two simultaneous excitations in an atomic ensemble are greatly suppressed,which makes it possible to excite a mesoscopic cold atomic ensemble into a near-ideal singly-excited symmetric collective state accompanied by a signal-photon with near unity success probability.     

双平行圆柱形MDM纳米棒等离子体波导的传输特性分析

设计了一种由双平行圆柱形纳米棒构成的金属-介质-金属(MDM)型等离子体波导,采用时域有限差分方法(FDTD)分析了波导结构的传输特性。当光波垂直主轴入射时,电磁场被很好地局限在两纳米棒所形成的中间区域以及介质层中,从而在该波导中能够有效地耦合电磁场能量。在工作波长为1 550 nm的情况下,随着内层金属芯半径的增大,有效折射率减小,传播距离增大;而中间介质层厚度增大时,有效折射率增大,传播距离减小。当外层金属壳厚为20 nm时,电场可以很好地被限制在纳米棒的介质层内。上述结果表明:通过调整波导结构的几何参数可以显著提高金属纳米棒的场限制,降低波导本身的损耗, 使波导的有效折射率和传播长度达到最优化。这种等离子体波导能够实现亚波长的光限制,可以应用于光子器件集成和传感器领域。     

带有增益介质层的混合脊状等离子体波导的传输特性

在传统脊状等离子体波导的基础上设计了一种带有增益介质层的新型混合脊状等离子体波导,其结构中的介质层部分包含两个区域:前区为单一介质,后区的脊是由2种介质构成的双层脊区。采用二维时域有限差分方法分析了波导结构的传输特性,得到了TM模下的电场分布图,并对输出功率以及传输损耗与结构参数和介质折射率的变化规律进行了讨论。结果表明,在波导中引入的增益介质材料磷化铟后其损耗达到-6 dB/μm。此种波导结构对于光集成芯片的研究与制作具有重要意义。     

Cross-Polarized Single Photon Emission from Single Semiconductor Quantum Dots with V-Type Level Driven by Pulse Field

The statistic properties of photon emissions from single semiconductor quantum dots with V-type level driven by pulses are investigated theoretically. Based on quantum regression theorem and master equations, the dynamic equations of the second-order correlation function of the photon emissions are deduced. The calculated results reveal that the efficiency of single photon emissions from two orthogonal polarization eigenstates （｜x） and ｜y） ） reaches the maximum when the input pulses area is about π, and the probability of the cross-polarized single photon emission from ｜x） and ｜y） decreases with increasing of pulse width.     

First-Principle Derivation of Single-Photon Entropy and Maxwell–Jüttner Velocity Distribution

This work is devoted to deriving the entropy of a single photon in a beam of light from first principles. Based on the quantum processes of light–matter interaction, we find that, if the light is not in equilibrium, there are two different ways, depending on whether the photon is being added or being removed from the light, of defining the single-photon entropy of this light. However, when the light is in equilibrium at temperature T, the two definitions are equivalent and the photon entropy of this light is hν/T. From first principles, we also re-derive the Jüttner velocity distribution showing that, even without interatomic collisions, two-level atoms will relax to the state satisfying the Maxwell–Jüttner velocity distribution when they are moving in blackbody radiation fields.     

Cross-Polarized Single Photon Emission from Single Semiconductor Quantum Dots with V-Type Level Driven by Pulse Field

The statistic properties of photon emissions from single semiconductor quantum dots with V-type level driven by pulses are investigated theoretically. Based on quantum regression theorem and master equations, the dynamic equations of the second-order correlation function of the photon emissions are deduced. The calculated results reveal that the efficiency of single photon emissions from two orthogonal polarization eigenstates |x〉and |y〉) reaches the maximum when the input pulses area is about π, and the probability of the cross-polarized single photon emission from |x 〉 and |y 〉decreases with increasing of pulse width.     

Al/ZnO:Al薄膜结构的荧光增强效应

利用物理气相沉积设备制备了Al/ZnO:Al薄膜样品,研究了该薄膜结构的发光特性。结果表明,在ZnO:Al薄膜表面镀一层Al岛薄膜可以增强其带边荧光,同时在475 nm附近产生蓝光峰。通过在Al岛薄膜和ZnO:Al薄膜之间引入一层5 nm的Ta₂O₅绝缘层可以使ZnO:Al薄膜的带边荧光和蓝光显著增强,并随着Ta₂O₅绝缘层厚度的增大而减弱。通过对Al/ZnO:Al样品进行退火处理可以使带边荧光和蓝光峰分别增强9倍和83倍。基于局域表面等离子体共振理论,计算了Al/ZnO:Al纳米结构的光学散射和吸收截面曲线。实验结果与理论计算相一致。     

溶胶-凝胶法纳米ZnO薄膜的绿光发射

利用溶胶-凝胶法制备了纳米ZnO薄膜,室温下测量了样品的光致发光谱(PL)和X射线衍射谱(XRD),观测到中心波长在523 nm附近的绿色荧光发射,研究了纳米ZnO薄膜的绿光发射机制,证实了纳米ZnO薄膜绿光可见发射带来自氧空位(Vo)形成的浅施主能级和锌空位(Vzn)形成的浅受主能级之间的复合。     

压力诱导发光未来可期

科技创新的根源是基于基础科学研究的提升,而"从0到1"的突破是需要长期的积累和灵感的。本文讲述了发现压力诱导发光这一新现象的思想和材料设计。     

Plasmonic sensor with self-reference capability based on functional layer film composed of Au/Si gratings

We propose a simple one-dimensional grating coupling system that can excite multiple surface plasmon resonances for refractive index(RI)sensing with self-reference characteristics in the near-infrared band.Using theoretical analysis and the finite-difference time-domain method,the plasmonic mechanism of the structure is discussed in detail.The results show that the excited resonances are independent of each other and have different fields of action.The mode involving extensive interaction with the analyte environment achieves a high sensitivity of 1236 nm/RIU,and the figure of merit(FOM)can reach 145 RIU-1.Importantly,the mode that is insensitive to the analyte environment exhibits good self-reference characteristics.Moreover,we discuss the case of exchanging the substrate material with the analyte environment.Promising simulation results show that this RI sensor can be widely deployed in unstable and complicated environments.     

大豆愈伤组织超弱光子辐射的双指数模型

在研究生物超弱光子辐射机理的基础上,建立了大豆愈伤组织超弱光子辐射的双指数模型.用20μW/cm2的UV-B辐射处理大豆愈伤组织2 h,测定处理后4 d内的超弱光子辐射.结果显示,双指数模型准确描述了大豆愈伤组织的超弱光子辐射及其在UV-B辐射下的变化,表明大豆愈伤组织的超弱光子辐射由快项和慢项两个部分组成;通过对双指...     

纳米ZnO薄膜可见发射机制研究

利用溶胶－凝胶法 （Sol-Gel）制备了纳米ZnO薄膜,获得了高强的近紫外发射室温下测量了样品的光致发光谱(PL )、吸收谱(ABS)、X射线衍射谱(XRD).X射线衍射(XRD)的结果表明：纳米ZnO薄膜呈多晶态,具有六角纤锌矿结构和良好的C轴取向;发现随退火温度升高,（002）衍射峰强度显著增强,衍射峰的半高宽（FWHM）减小、纳米颗粒的粒径增大.由吸收谱(ABS)给出了样品室温下带隙宽度为3.30 eV.在PL谱中观察到二个荧光发射带,一个是中心波长位于392 nm附近强而尖的紫带,另一个是519 nm附近弱而宽的绿带研究了不同退火温度样品的光致发光峰值强度的变化关系,发现随退火温度升高,紫带峰值强度增强、绿带峰值强度减弱,均近似呈线性变化.证实了纳米ZnO薄膜绿光发射主要来自氧空位(Vo)形成的浅施主能级与锌空位(VZn)形成的浅受主能级之间的复合,或氧空位(Vo)形成的深施主能级上的电子至价带顶的跃迁;紫带来自于导带中的电子与价带中的空位形成的激子复合.     

Phonon Band Filling and Photon Emission by Phonons

Phonon generation by electrons is supplied in n-type Si crystals in electric fields E100 kV/cm at the lattice temperature of 80 K employing the ensemble Monte Carlo technique. Electron transfer between equivalent energy valleys is accounted for the g-type- and f-type phonon absorption and emission. Acoustic phonons are accounted for the quasi-elastic scattering of electrons within the energy valleys. Excess phonon number is determined using numerical data on phonon generation rate and experimental values of phonon lifetimes. The feasibility of stimulated emission of infrared-range photons due to direct optical transitions between the phonon bands is discussed.     

常见场致发射阴极材料的发射特性

利用三阴极加速器平台,对不锈钢、黄铜、铝、天鹅绒和石墨等几种常见场致发射材料的电流发射能力、相对启动延迟时间及其抖动进行了实验研究。实验结果表明：在二极管电压近似恒定时,不锈钢阴极启动时间延迟抖动小于8 ns,天鹅绒阴极及石墨阴极启动时间延迟抖动小于4 ns;且材料在阴极频繁工作时启动时间加快;常见金属材料中不锈钢阴极的综合性能较好;非金属材料中,天鹅绒阴极的发射能力最强,且发射延迟时间最短,但考虑到天鹅绒材料严重的出气问题,非金属材料中以石墨阴极的性能为优。