High power output quasi-continuous-wave nanosecond optical parametric generator based on periodically poled lithium niobate

We report on a high power output quasi-continuous-wave nanosecond optical parametric generator （OPG） of congruent periodically poled lithium niobate （PPLN） pumped by a 1 064 nm acousto-optically Q-switched Nd-YVO4 laser （duration. 70 ns,repetition rate：45 kHz,spatial beam quality M2〈 1,3）. The OPG consists of a 38.7 mm long PPLN crystal with a domain period of 28.93 μm. With 5.43 W of average pump power the maximum average output power is 991 mW at 1 517.1 nm signal wave of the PPLN OPG.     

Cu掺杂对ZnO量子点光致发光的影响

通过溶液法合成了Cu掺杂ZnO量子点。X射线衍射(XRD)和高分辨电子透射电镜(HRTEM)图像显示Cu掺杂ZnO量子点具有六角纤锌矿结构,晶粒大小为4～5nm。Cu掺杂抑制了ZnO量子点颗粒长大。室温光致发光(PL)谱观察到紫外带边和可见区两个发射峰。随着Cu掺杂浓度的增大,紫外荧光峰位发生缓慢红移,由366nm移到370nm;可见区发射峰位发生蓝移,由525nm移到495nm;同时,两个发射峰强度降低。光谱结果表明:Cu的掺入,一方面抑制表面与O空位有关的缺陷,在495nm出现了与Cu1+有关的发射峰;另一方面,Cu离子掺入ZnO量子点引入一些非辐射中心,降低了自由激子发射。     

Electron effective mass in InuGa1−uPvAs1−v for 0 ≤ v ≤ 1

The electron effective mass in In_uGa_1−uP_vAs_1−v has been measured on seven samples lattice-matched to InP and evenly spaced in values of v between 0 and 1, using the temperature dependence of the amplitude of the Shubnikov-de Haas oscillations at high magnetic fields. Values of the carrier concentrations, Hall mobilities and Dingle temperatures measured on these samples are also reported. Work sponsored in part by the National Science Foundation, Grant No. ENG 76-09586, and in part by International Telephone and Telegraph Electro-Optical Products Division. Work done in part at the M.I.T. Francis Bitter National Magnet Laboratory. Funded in part by the National Science Foundation under Grant No. DMR-76-80895.     

Fabrication of flexible organic light-emitting diodes with Alq3 as emitting layer

Fabrication of flexible organic light-emitting diodes（FOLEDs） with ITO/PVK ：TPD/Alq3/Al configuration prepared on PET substrates is reported. Alq3 is used as the light-emitting material. The curves of the current density vs. voltage,optical current vs. voltage and quantum efficiency vs. current density of the devices are investigated. Compared the devices with the ones that have the same configuration and are fabricated under the same conditions but on glass substrates,the characteristics of the two kinds of devices are very similar except that the threshold voltage of the flexible FOLEDs is a little higher. Under the driving voltage of 20V,the corresponding brightness and the external quantum efficiency are 1000 cd/m^2 and 0. 27%, respectively. In addition, the anti-bend ability of the devices is tested and the reasons of failure of the devices are analyzed.     

Fluorescence enhancement of single-phase red-blue emitting Ba3MgSi2O8:Eu2+,Mn2+ phosphors via Dy3+ addition for plant cultivation

Fluorescence enhancement of red and blue concurrently emitting Ba₃MgSi₂O₈:Eu²⁺,Mn²⁺ phosphors for plant cultivation has been investigated by Dy³⁺ addition. The Ba₃MgSi₂O₈:Eu²⁺,Mn²⁺,Dy³⁺(BMS-EMD) phosphors have two-color emissions at the wavelength peak values of 437 nm and 620 nm at the excitation of 350 nm. The two emission bands are coincident with the absorption spectrum for photosynthesis of plants. An obvious enhancement effect has been observed upon addition of Dy³⁺ with amount of 0.03 mol%, in which the intensities of both blue and red bands reach a maximum. The origin of red and blue emission bands is analysed. The photochromic parameters of the samples at the nearly UV excitation are tested. This fluoresence enhancement is of great significance for special solid state lighting equipment used in plant cultivation. This work has been supported by National Natural Science Foundation of China (Grant No 50872091) and the Natural Science Foundation of Tianjin, China (06YFJMJC02300, 06TXTJJC14602).     

High performance blue organic light-emitting devices fabricated by using the doped AIq3 in NPB hole transmistion layers

We have designed a new structure blue emission device with doped Alq3 of 3% in hole transmission layers of NPB. The CIE coordination of the devices is （0.17,0.19）. The maximum electroluminescence efficiency is 4.1 cd/A at 11 V, the brightness is 118.8 cd/m^2 at 7 V, and the maximum brightness is 10770 cd/m^2 at 13 V.     

Optical study of InP quantum dots

Results of photoluminescence (PL) studies of self-organized nanoscale InP islands (quantum dots, QDs) in the In_0.49Ga_0.51P matrix, grown on a GaAs substrate by metalorganic vapor phase epitaxy (MOVPE), are presented. Dependences of the PL efficiency on temperature in the range 77–300 K and on excitation level at pumping power densities of 0.01–5 kW/cm² have been obtained. The PL spectra are a superposition of emission peaks from QDs and the wetting layer. Their intensity ratio depends on the pumping power and temperature, and the emission wavelength varies in the range 0.65–0.73 μm. At 77 K and low excitation level, InP QDs exhibit high temperature stability of the emission wavelength and high quantum efficiency. __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 35, No. 2, 2001, pp. 242–244. Original Russian Text Copyright ? 2001 by Vinokurov, Kapitonov, Nikolaev, Sokolova, Tarasov.     

Teleportation of an arbitrary unknown N -qubit entangled state under the controlling of M controllers

A new quantum protocol to teleport an arbitrary unknown N-qubit entangled state from a sender to a fixed receiver under M controllers（M 〈 N） is proposed. The quantum resources required are M non-maximally entangled Greenberger-Home- Zeilinger （GHZ） state and N-M non-maximally entangled Einstein-Podolsky-Rosen （EPR） pairs. The sender performs N generalized Bell-state measurements on the 2N particles. Controllers take M single-particle measurement along x-axis, and the receiver needs to introduce one auxiliary two-level particle to extract quantum information probabilistically with the fidelity unit if controllers cooperate with it.     

Effect of exit and injection rates on phase-dependent transient evolution of gain without inversion

It is shown that in an open Λ-type system with spontaneously generated coherence, the transient evolution rule of the gain of lasing without inversion (LWI) is very sensitive to variation of the relative phase φ between the probe and driving fields; the variety of the atomic exit rateγ_0 and the ratio C of the atomic injection rates also have a considerable effect on the phase-dependent transient evolution rule of LWI gain. We find that whenφ=0, the transient and stationary LWI gain increases with C increasing but decreases with γ_0 increasing; whenφ≠0 , the effect of C andγ_0 on LWI gain is just opposite to that when φ=0 ; in order to get the largest transient and stationary LWI gain, we need selecting suitable values of φ,γ_0 and C.     

Solvent‐Polarity‐Engineered Controllable Synthesis of Highly Fluorescent Cesium Lead Halide Perovskite Quantum Dots and Their Use in White Light‐Emitting Diodes

Cesium lead halide quantum dots (QDs) have tunable photoluminescence that is capable of covering the entire visible spectrum and have high quantum yields, which make them a new fluorescent materials for various applications. Here, the synthesis of CsPbX₃ (X = Cl, Br, I, or mixed Cl/Br and Br/I) QDs by direct ion reactions in ether solvents is reported, and for the first time the synergetic effects of solvent polarity and reaction temperature on the nucleation and growth of QDs are demonstrated. The use of solvent with a low polarity enables controlled growth of QDs, which facilitates the synthesis of high‐quality CsPbX₃ QDs with broadly tunable luminescence, narrow emission width, and high quantum yield. A QD white LED (WLED) is demonstrated by coating the highly fluorescent green‐emissive CsPbBr₃ QDs together with red phosphors on a blue InGaN chip, which presents excellent warm white light emission with a high rendering index of 93.2 and color temperature of 5447 K, suggesting the potential applications of highly fluorescent cesium lead halide perovskite QDs as an alternative color converter in the fabrication of WLEDs.     

Design and fabrication of sub-μs silicon-on-insulator thermo-optic 4×4 switch matrix

A rearrangeable nonblocking silicon-on-insulator-based thermo-optic 4x4 switch matrix with spot size converters （SSCs） and a new driving circuit are designed and fabricated. The introduction of a spot size converter （SSC） has decreased the insertion loss to less than 10dB and the new driving circuit has improved the response speed to less than l~s.     

Photoluminescence origin of nanocrystalline SiC films

The nanocrystalline SiC films were prepared on Si then annealed at 800℃ and 1 000℃ for 30 minutes （111） substrates by rf magnetron sputtering and in a vacuum annealing system. The crystal structure and crystallization of as-annealed SiC films were determined by the Fourier transform infrared （FIR） absorption spectra and the X-ray diffraction （XRD） analysis. Measurement of photoluminescence （PL） of the nanocrystalline SiC （nc-SiC） films shows that the blue light with 473 nm and 477 nm wavelengths emitted at room temperature and that the PL peak shifts to shorter wavelength side and the PL intensity becomes stronger as the annealing temperature decreases. The time-resolved spectrum of the PL at 477 nm exhibits a bi-exponential decay process with lifetimes of 600 ps and 5 ns and a characteristic of the direct band gap. The strong blue light emission with short PL lifetimes suggests that the quantum confinement effect of the SiC nanocrystals resulted in the radiative recombination of the direct optical transitions.     

Robust and Stable Ratiometric Temperature Sensor Based on Zn–In–S Quantum Dots with Intrinsic Dual‐Dopant Ion Emissions

Dual emission quantum dots (QDs) have attracted considerable interest as a novel phosphor for constructing ratiometric optical thermometry because of its self‐referencing capability. In this work, the exploration of codoped Zn–In–S QDs with dual emissions at ≈512 and ≈612 nm from intrinsic Cu and Mn dopants for ratiometric temperature sensing is reported. It is found that the dopant emissions can be tailored by adjusting the Mn‐to‐Cu concentration ratios, enabling the dual emissions in a tunable manner. The energy difference between the conduction band of the host and Cu dopant states is considered as the key for the occurrence of Mn ion emission. The as‐constructed QD ratiometric temperature sensor exhibits a totally robust stability with a fluctuation of ≈I_Cu/I_tot versus times lower than 1% and almost no hysteresis in cycles over a broad window of 100–320 K. This discovery represents that the present cadmium‐free, intrinsic dual‐emitting codoped QDs can open a new door for the synthesis of novel QDs with stable dual emissions, which poise them well for challenging applications in optical nanothermometry.     

Improved area density and luminescence properties of InP quantum dots grown on In<Subscript>0.5</Subscript>Al<Subscript>0.5</Subscript>P by metal-organic chemical vapor deposition

We report on the growth of InP self-assembled quantum dots (QDs) on In_0.5Al_0.5P matrices by metal-organic chemical vapor deposition (MOCVD) on (001) GaAs substrates. The effects of the growth temperature and V/III-precursor flow ratio on the areal density and the cathodoluminescence (CL) properties of the grown QDs were systematically studied. We found that, when the growth temperature is ≤630°C, coherent QDs as well as large dislocated InP islands can be observed on the matrix surface. However, by using a two-step growth method, i.e., by growing the InAlP matrix layer at higher temperatures and growing InP QDs at lower temperatures, the formation of large dislocated islands can be effectively suppressed. Moreover, the areal density of the InP QDs is increased as the QD growth temperature is reduced. Furthermore, we found that the V/III ratio used in growing QDs and in growing the InAlP matrix layers has a quite different effect. In growing QDs, decreasing the V/III ratio results in an increase in the CL intensity and a decrease in CL line width; while in growing the InAlP matrix layers, increasing the V/III ratio results in an increase in the CL intensity of the InP QDs.     

Dynamical control of directional nonlinear scattering from metallic nanoantennas by three-dimensional focal polarization orientation

We demonstrate that the directionality of far-field second harmonic(SH) emission generated from individual gold nanosphere can be flexibly engineered by manipulating three-dimensional(3D) focal polarization orientation of the excitation field, which is explained by the coherent interference between SH dipolar and quadrupolar emission modes. The SH dipolar emission mode is independent of the polarization direction of the fundamental field whereas the evolution of the focal polarization orientation can dramatically modify the quadrupolar emission pattern. Therefore, the resultant SH emission pattern has a polarization-dependent behavior and side scattering almost perpendicular to the propagation direction of the incident light can be observed under a specific condition. Our findings provide a novel degree of freedom for all-optical control of directional nonlinear scattering from single nanoantenna, thereby opening new possibilities for future potential applications.     

Cover Picture: Highly Fluorescent Poly(dimethylsiloxane) for On‐Chip Temperature Measurements (Adv. Funct. Mater. 2/2009)

This work describes a convenient method to generate a poly(dimethylsiloxane) (PDMS) composite containing ZnO quantum dots (QDs) for whole‐chip temperature measurements. This composite is highly fluorescent and very sensitive to temperature changes (0.4 nm °C⁻¹, compared to 0.1 nm °C⁻¹ in commonly used CdSe QDs). It also shows extremely high fluorescent stability under various conditions over long time without phase separation or fluorescent changes. Both merits make this composite an ideal material for sensing temperature changes on microfluidic chips. The bonding between the QDs and PDMS is studied by comparing PDMS composites with ZnO QDs of different sizes, and a model is given to elucidate the high stability of this composite.     

The nonlinear optical properties of P3HT under picosecond laser irradiation

The nonlinear optical properties of P3HT in orthodichlorobenzene were investigated by Z-scan technique using second harmonic generation(532 nm) of mode-locked Nd:YAG laser in the picosecond domain. The experimental results show the magnitude of their nonlinear refraction indices was up to the order of 10^-11 esu. The reverse saturable absorption of P3HT solution was observed and their nonlinear absorption coefficients reach up to 3.4 cm/GW. The strong optical nonlinearity of P3HT may find its new application in the photoclectric field.     

Temperature characteristics of InGaAs/GaAs vertical cavity surface emitting laser

The temperature characteristics for the different lasing modes at 300 K of intracavity contacted InGaAs/GaAs Vertical Cavity Surface Emitting Lasers（VCSELs） have been investigated experimentally by using the SV-32 cryostat and LD200205 test system. In combination with the simulation results of the reflective spectrum and the gain peak at different temperatures, the measurement results have been analyzed. In addition, the dependence of device size on temperature characteristics is discussed. The experimental data can be used to optimally design of VCSEL at high or cryogenic temperature.     

Electroluminescence of injection lasers based on vertically coupled quantum dots near the lasing threshold

Electroluminescence spectroscopy has been used in a wide range of temperatures (77–300 K) and driving current densities to study a laser heterostructure based on vertically coupled self-assembled InGaAs quantum dots (QD). It has been found that lasing occurs via the QD ground state in the entire temperature range. The temperature-independent position of the emission peak corresponding to the second excited state in QDs is explained.     

Effects of Varying MBE Growth Conditions on Layered Zn-Se-Te Structures

We report the effects of varying growth parameters on the photoluminescence (PL) and time-resolved photoluminescence (TRPL) emission from layered Zn-Se:Te structures with submonolayer quantities of ZnTe grown by a combination of migration-enhanced epitaxy (MEE) and molecular beam epitaxy (MBE). Dependences on Te effusion cell temperature (T _{Te source}) and “wait time” (duration for which all shutters are closed, t _all-off) are investigated to show that these parameters contribute towards changing the size and/or composition of the quantum dots (QDs). Optical studies showed that increasing T _{Te source} resulted in the formation of larger QDs. Increasing t _all-off from 0 s to 3 s contributed towards the formation of larger QDs, while further increasing t _all-off to 9 s led to desorption of Te adatoms which resulted in smaller QDs. These parameters are easy to control, and thus understanding their effects should help us to gain better control towards obtaining high-quality QDs.