基于溶液加工小分子材料发光层的有机-无机复合发光器件

报道了基于溶液加工有机小分子材料发光层、聚乙烯亚胺电子注入层的有机-无机复合发光器件. 优化了空穴传输层和磷光染料的掺杂浓度, 得到最佳发光效率的器件. 蓝光、黄光和红光器件的最大外量子效率为17.3%, 10.7% 和7.3%. 在发光亮度为1000 cd/m² 时, 蓝光、黄光和红光器件的外量子效率分别为17.0%, 10.6% 和5.8%, 器件效率下降较小. 原因在于同时采用空穴传输型和电子传输型的小分子材料作为共同主体材料, 器件具有较宽的载流子复合区域, 降低了三线激发态-三线激发态湮灭和三线激发态-极化子相互作用对器件发光效率的影响. 白光器件在亮度为1000 cd/m²时, 发光效率和功率效率为31 cd/A和 14.8 lm/W. 器件的色度为(0.32, 0.42), 色度比较稳定, 随电流的变化微小. 器件的效率较以往报道的有机-无机复合发光器件有显著的提高, 主要归因于在聚乙烯亚胺上能够制备特性良好的小分子材料薄膜, 以及小分子主体材料拥有较高的三线态能量和平衡的载流子传输特性, 能够获得高效的磷光发射.     

Wavelength-tunable high-power picosecond pulses from a fiber-pumped diode-seeded high-gain parametric amplifier

We describe a high-gain optical parametric amplifier (OPA) and optical parametric generator (OPG) system pumped by a fiber chirped-pulse amplification source based on novel large-mode-area fiber components. 45-nJ OPG thresholds and 34% pump-signal conversion efficiencies are obtained for ~4-ps pulses. OPA gains in excess of 75 dB and pump-signal conversion efficiencies of ~39% (external) are demonstrated. Furthermore, we show that injection seeding of such high-gain parametric devices by use of a low-power continuous-wave beam results in high-power (>18-kW) picosecond pulses with a time-bandwidth produce of ~0.65, some ten times less than from a free-running OPG. Using such an approach, we obtain 2.7-ps 50-nJ pulses at 1.310 mum .     

Luminescence properties of poly(9,9-dioctylfluorene)/polyvinylcarbazole blends: Role of composition on the emission colour stability and electroluminescence efficiency

Light-emitting diodes (LEDs), based on blue-emitting polyfluorenes are usually prone to the appearance of a contaminant green emission (centered around 520 nm), leading to an apparent whitish light emission. We find that, for LEDs based on poly(9,9-dioctylfluorene), PFO, the blending with the hole transporting polyvinylcarbazole, PVK, can suppress such green emission. LEDs based on a PFO/PVK blend with a 1:2 weight ratio and with aluminum cathodes show a quite stable blue emission. This result reveals the important role played by the interchain interactions on the observed contaminant green emission. In addition, we observe that in Al-based devices blending causes a decrease in EL efficiency while in Mg-based devices we obtained higher efficiencies with the blend PFO:3PVK when compared with neat PFO-based devices.     

Low-threshold-current CW injection lasers

In this paper we report on the properties and structure of oxide-defined stripe-geometry lasers with cw threshold currents as low as 27mA at room temperature. These results have been obtained by the addition pf a dielectric facet reflector and use of a thin “cap” structure that limits the current spreading. These devices are capable of output powers up to 60mW from one facet with power conversion efficiencies up to 14%.     

Degenerate four-wave mixing in InSb at 5K

We report the observation of degenerate four-wave mixing in InSb at 5 K using a cw CO laser operating in the spectral region just below the bandgap energy, where strong self-defocusing and optical bistability have previously been seen. Conversion efficiencies of ≈1% are obtained with <13 mW beam powers, and higher efficiencies are predicted for improved phase-matching.     

A simple encapsulation method for organic optoelectronic devices

The performances of organic optoelectronic devices, such as organic light emitting diodes and polymer solar cells,have rapidly improved in the past decade. The stability of an organic optoelectronic device has become a key problem for further development. In this paper, we report one simple encapsulation method for organic optoelectronic devices with a parafilm, based on ternary polymer solar cells(PSCs). The power conversion efficiencies(PCE) of PSCs with and without encapsulation decrease from 2.93% to 2.17% and from 2.87% to 1.16% after 168-hours of degradation under an ambient environment, respectively. The stability of PSCs could be enhanced by encapsulation with a parafilm. The encapsulation method is a competitive choice for organic optoelectronic devices, owing to its low cost and compatibility with flexible devices.     

Effect of oxide aperture on the performance of 850 nm vertical-cavity surface-emitting lasers

An experimental study has been presented of the oxide-confined vertical-cavity surface-emitting lasers (VCSELs) operating in the 850 nm region of the electromagnetic spectrum. In this regard, various relevant VCSEL samples with numerous oxide aperture sizes have been fabricated and characterized. Thorough investigations of the electrical as well as optical characteristics of the fabricated samples have been performed, which include the overall device performance as a function of the oxidize aperture sizes. It is reported that the VCSELs with oxide aperture size <10 μm require low threshold currents (<1 mA). Further, the differential quantum efficiencies up to 28% corresponding to wall-plug efficiencies of up to 15% were measured for a number of these devices.     

氮化铌纳米线光学特性

氮化铌(NbN)纳米线是超导纳米线单光子探测器(SNSPD)常用的光敏材料,其光学性质是影响SNSPD性能的关键因素.本文结合实验数据和仿真结果,系统研究了多种NbN超导纳米线探测器器件结构的光学特性,表征了以下四种器件结构下的反射光谱以及透射光谱:1)双面热氧化硅衬底背面对光结构;2)双面SiN硅衬底背面对光结构;3)硅衬底上以金层+SiN缓冲层为反射镜的正面对光结构;4)以分布式布拉格反射镜(DBR)为衬底的正面对光结构.并在上述四种器件结构基础上,生长了不同厚度的NbN薄膜,观察不同厚度NbN薄膜的吸收效率.经分析,发现在不同器件结构下的最佳NbN厚度与光吸收率的关系如下:双面热氧化硅衬底上的NbN层在1606 nm处最大吸收率为91.7%,其余结构在最佳NbN厚度条件下吸收率都能达到99%以上.其中双面SiN的硅衬底结构中最大吸收率为99.3%, Au+SiN为99.8%, DBR为99.9%.最后,将DBR器件实测结果与仿真结果进行了差异性分析.这些结果对高效率SNSPD设计与研制具有指导意义.     

Performance curves comparison of THG efficiency in CsLib6O10 on flattened Gaussian and Gaussian beams

The conversion efficiency of THG on the flattened Gaussian and Gaussian beams is obtained in detail numerical stimulation for CsLiB6O10.The conversion efficiencies of 86.7% and 96% of the flattened Gaussian are larger than those of Gaussian beams of 72.6% and 88% under type I and type 11(1) phase matching. The efficiencies affected by the pump intensity, polarization rate, crystal lengths and orders of the flattened Gaussian beams were presented.     

Measurement of strong photon recycling in ultra‐thin GaAs n/p junctions monolithically integrated in high‐photovoltage vertical epitaxial heterostructure architectures with conversion efficiencies exceeding 60%

Photon‐recycling effects are studied experimentally in photovoltaic power converting III–V semiconductor devices designed with the vertical epitaxial heterostructure architecture (VEHSA). The responsivity of VEHSA structures with multiple thin GaAs n/p junctions is measured for various optical input powers and for different wavelength detuning values with respect to the peak of the spectral response. While the detuning of the optical excitation decreases the external quantum efficiency and the responsivity at low input powers, this study demonstrates that at high optical intensities, a large fraction of the performance can be recovered despite significant detuning values. The photon coupling effects therefore broaden the spectral range for which the VEHSA devices convert high‐power optical inputs with high efficiencies into an electrical output having a preset voltage. The devices exhibit a near optimum responsivity of up to 0.645 A/W for tuned excitation conditions or at high optical intensities for spectral detuning values of up to ～25 nm and corresponding to an external quantum efficiency of ～94%. Efficiencies of 62.0% and 61.8% have been obtained for current‐matched excitations and for a detuning of >10 nm, respectively. An output power of 5.87 W is reported and an open circuit voltage enhancement of 92 meV per n/p junction is measured compared to a device with a side by side planar architecture. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

The high-power sliding-spark capillary discharge in vacuum: Variations and applications

High-power sliding-spark capillary discharges in vacuum may be operated so as to obtain soft x-ray radiation that is dominated by either line emission or continuum emission. In the latter case, black-body emission is obtainable with emission efficiencies exceeding 30% of input power. Adjustments in the spectral output of the discharge are achievable either with a conically tapered capillary or with electron-beam assisted heating of the discharge. Such devices are useful for high-resolution contact microscopy of wet, unstained, thin biological samples as well as for lithography.     

DFB lasers with integrated electroabsorption modulator

We present high-performance 1550 nm DFB lasers with butt-coupled, bulk type integrated electroabsorption modulators of good manufacturability and reliability. Key issues in device design are reviewed and the strong influence of the exact detuning between lasing wavelength and modulator bandgap is demonstrated. Fibre-coupled output powers as large as 6 dBm and attenuation efficiencies as high as 12 dB V^–1 are obtained. Butterfly-packaged devices show only 1 dB penalty for 10 Gbit s^–1 NRZ transmission over 50-km standard single-mode fibre (SMF) without the use of an optical amplifier. With an optical booster amplifier, self-phase-modulation in the fibre is exploited and repeaterless 10 Gbit s^–1 transmission is possible over 150-km standard SMF.     

光栅腔BBO光参量振荡器

报道０．５３２μｍ泵浦的光栅腔ＢＢＯ光参量振荡器的实验研究结果，在１．０２－１．０８μｍ可调谐范围内，其输出线宽小于１ｎｍ，参量转换效率为３．５％。     

Intensely emitting CdTe nanocrystals retained initial photoluminescence efficiency in sol–gel derived Si<Subscript>1-x</Subscript>Zr<Subscript>x</Subscript>O<Subscript>2</Subscript> glass

Emitting CdTe nanocrystals (NCs) were embedded in pure glass matrices (Si_1-xZr_xO₂, x≤0.15) using a controlled sol–gel method, where the pre-hydrolyzed condition, the molar ratio of Zr/Si, the gelation time, the pH, and the amount of alcohol were judiciously optimized considering the surface condition of the NCs and the mechanism of the glass formation. As a result, the prepared glass phosphor exhibited high photoluminescence efficiencies (40% for green and 60% for red when Zr/Si was 5–10%) by retaining their initial values as in CdTe colloidal solution. To our knowledge, these values are the highest among those ever obtained for any solid matrices containing NCs. Because of the existence of Zr, the prepared glasses exhibit much better resistance against the ambient atmosphere, heat-treatment, and boiling water compared with pure silica glass (x=0) or the glass prepared from our other methods using a silane coupling agent. Thus, the obtained glass is promising for applications such as optical devices. PACS 78.67.Bf; 78.55.Qr; 78.55.Et     

Periodically poled lithium niobate monolithic nanosecond optical parametric oscillators and generators

We fabricated and characterized periodically poled lithium niobate monolithic optical parametric oscillators (OPO's) and generators. The compact monolithic devices were trivial to align and operate and provided widely tunable, nearly diffraction-limited, stable output pulses. Low thresholds and high conversion efficiencies were obtained when the devices were pumped with 3.5-ns 1.064-mum pulses. In addition, the monolithic OPO devices exhibited broad tuning by crystal rotation through noncollinear phase matching. The bandwidth-broadening effects exhibited in the noncollinear phase-matching geometry were measured and explained.     

Intracavity second-harmonic generation of chemical oxygen-iodine laser emission using a LBO crystal

Intracavity second-harmonic generation of continuous-wave chemical oxygen-iodine laser emission has been studied. A chemical oxygen-iodine laser with a maximum fundamental-wave output power of about 10 W in a concentric cavity was used. Experiments were performed for three types of optical cavities using an 1 cm LBO crystal. Second-harmonic output of 12.4 W, 6.2 W, and 5.2 W, effective extraction efficiencies of 155.0% 65.9%. and 55.3%, and single-pass conversion efficiencies of 0.615%, 0.685%, and 0.655% were obtained for the respective cavities. A comparison of these results of coupling by frequency doubling with the results of fundamental-wave output coupling of this system is also presented.     

The effect of annealing procedures on photoluminescence and electroluminescence in ZnTe

The effects of elevated temperature annealing procedures on the photoluminescent properties of ZnTe crystals were investigated. The materials studied included nominally-undoped, phosphorus-doped and oxygen-doped crystals. As a result of annealing in Zn vapor at temperatures of 850°C for periods of 65 hr the radiative recombination associated with the isoelectronic oxygen center was enhanced by a factor of five times. Correlation existed between the photoluminescent properties of the crystals and the electroluminescent properties of M.I.S. devices. Photoluminescence measurements on the grown crystals are considered to provide a reliable indication of potential device performance. For M.I.S. devices fabricated from annealed crystals by a technique in which a compensated layer was produced by Al diffusion and a contact applied by an In alloying procedure, room-temperature external quantum efficiencies up to 10⁻³ photons/electron were obtained for the 1·8 eV emission associated with the isoelectronic oxygen center.     

基于宽光谱应用的波长解复用多重体光栅的光写入特性

针对光通信中波长覆盖范围日益增宽的特点,从理论上研究了用于宽光谱范围波长解复用器件的多重体光栅的布喇格匹配和各波长对应光栅衍射效率的均匀性.计算及实验结果均表明,由于记录介质的色散效应将导致多重体全息光栅读出过程中明显的布喇格失配,并且在写入过程中获得的均匀折射率调制度的多重体光栅,在读出过程中各通信波长对应光栅的衍射效率将不均匀为此,提出了改进多重体光栅的光写入方法,给出了利用角度复用法写入透射型多重体光栅时解复用波长与写入角度的关系,以及写入体光栅过程中记录介质的折射率调制度修正公式.     

Measuring efficiency of positive and negative ionic wind devices for comparison to fans and blowers

Many industries are pursuing alternate air moving devices to reduce the power consumption of their air cooled products. The literature suggests that ionic AMDs have low efficiency. The literature, however, does not define efficiency the same way the computer industry defines it for rotary AMDs. In this study, static efficiency of ionic AMDs was evaluated similar to rotary AMDs. Various emitter to collector distances and various ring lengths, were evaluated for positive and negative coronas. By controlling emitter to collector distance and collector length, efficiencies were obtained more reasonably compared to rotary devices.     

Optimization of electro-optical characteristics of GaAs-based oxide confinement VCSEL

An experimental study has been presented of the oxide-confined vertical-cavity surface-emitting lasers (VCSEL) operating in the 850 nm region of the electromagnetic spectrum. In this regard, various relevant VCSEL samples with numerous oxide aperture sizes have been fabricated and characterized. Thorough investigations of the electrical as well as optical characteristics of the fabricated samples have been performed which includes the overall device performance as a function of the oxidize aperture sizes. It is reported that the VCSEL with oxide aperture size <10 μm require low threshold currents (<1 mA). Further, the differential quantum efficiencies up to 28% were measured for a number of these devices. It is found that devices employing oxide aperture of 10 to 15 μm shows promising electro-optical characteristics for 850 nm oxide VCSEL optimization.