Optoelectronics in satellite designs

Design of artificial satellites for communication, remote sensing and scientific investigations follows, at present, a fixed pattern based on existing and proven technologies and the requirements of payload or experiment within the constraints of weight, volume and power available. The advances in optoelectronic components and systems have opened up a new dimension in designing satellites of the future, incorporating new technologies. This paper deals with general satellite design concepts based on optoelectronic systems wherever applicable.     

Long wavelength quantum well lasers: Synopsis of the RACE “AQUA” project: MOVPE/MBE/GSMBE for InGaAsP/InP and InGaAlAs/InP high speed MQW DFB lasers

The technological limits for ultra high speed devices are now rapidly expanding due to the use of quantum well (QW) materials. This new class of materials gives the opportunity of tailoring materials parameters by controlling geometries on an atomic scale. They look very promising as materials for lasers, detectors and transistors suitable even above 10 Gb/s. It will be demonstrated that state of the art MQW structures can be realized in both material systems, InGaAsP/InP and InGaAlAs/InP. Parallel lateral laser structures (e.g. SIBH, BRS and TBH) have been designed to take full benefit of QW technology. Ultimate reduction of parasitics, whilst using potential low cost fabrication technologies is the basis for achieving high bitrate (10 Gb/s) MQW lasers, even with the stronger damping in QW material. Using the DFB-SIBH laser structure 10 Gb/s large signal experiments are successfully performed with bulk, MQW and SLMQW lasers. Extremely low fall times of 44 ps are achieved. Additional MQW based improvements are observed such as: −3 times higher differential gain, increased output power (>110 mW), 2.5 times lower chirp (Δλ_−20dB = 0.40 nm at 10 Gb/s modulation), and 2 dB gain in power budget at 10 Gb/s digital transmission.     

Exploring the potential of boron-doped nanographene as efficient charge transport and nonlinear optical material: A first-principles study

Owing to their excellent electrochemical properties, graphenes found applications in several fields ranging from semiconductors, solar cells, field effect transistors, and nanoscale electronic devices as well as in nonlinear optical (NLO) applications. The structural features, electro-optical, charge transport and nonlinear optical properties of the boron-doped graphene (BG) compound 1 were studied using density functional theory methods The BG compound comprises a central electron deficient site of boron atoms, which can serve as electron acceptor while terminal alkoxy groups as donors leading to powerful donor-π-acceptor (D-π-A) configuration. The experimental crystal structure was successfully reproduced by optimized ground state geometry at PBE0/6-311G* level of theory for isolated molecule. The experimental lattice parameters, geometries, crystal presentation and alignment of molecules in the unit cells as well as their packing orientation of BG compound 1 was also efficiently reproduced by applying periodic boundary conditions (PBC) at PBE level. The comprehensive intramolecular charge transfer (CT) was realized from terminal rings of the HOMO to the electron deficient sites of boron atoms of the LUMO. The nature of BG compound 1 might be more towards hole transport even though its hole reorganization energy is twice than that of the electron one due to the significant higher hole transfer integral values. The superior hole transfer integrals and intrinsic mobility values of the BG compound 1 might lead remarkable hole transport contender as compared to many other organic materials. The narrow band gap, density of states profile, dielectric function, uniform conductivity functions and noteworthy electronic as well as CT properties revealed that the BG compound 1 might be proficient optoelectronic contestant having intermolecular CT as well as intramolecular CT with optimal stability. A comparison of static third-order polarizability <γ> of BG compound 1, as calculated in present investigation, was also performed with some standard NLO molecules as well as graphene nanoflakes. Moreover, longitudinal component γ_zzzz of parent compound has been found 12 and 4 times larger than those of previously reported open-shell poly aromatic hydrocarbons (PAH). Interestingly, by increasing the donor ability, i.e., introduction of C₂H₂PhNH₂ groups in place of OC₄H₉ groups (BG compound 3) at terminal positions boosts the <γ> amplitude ∼ 8 times than that of its parent BG compound 1.     

玻璃中离子注入的进展

玻璃中离子注入的进展王承遇，王波，陶瑛（大连轻工业学院玻璃及无机新材料研究所１１６００１）ＴｈｅＤｅｖｅｌｏｐｍｅｎｔｏｆＩｏｎ－ＩｍｐｌａｎｔｉｏｎｉｎＧ１ａｓｓｅｓ￥ＷａｎｇＣｈｅｎｇｙｕ；ＷａｎｇＢｏ；ＴａｏＹｉｎｇ（ＩｎｓｔｉｔｕｔｅｏｆＧｌ...     

A Precursor‐Based Route to ZnSe Nanowire Bundles

A large number of one‐dimensional bundles of ZnSe nanowires with diameters ranging from 15–20 nm and lengths of up to tens of micrometers have been prepared via the thermal treatment of a ribbon‐like precursor (ZnSe·3ethylenediamine), which has been synthesized by a mixed solvothermal route, in an argon atmosphere. The as‐obtained precursor has been characterized by powder X‐ray diffraction (XRD), transmission electron microscopy (TEM), IR spectroscopy, thermogravimetric analysis, and elemental analysis. XRD and high‐resolution TEM characterization reveal that the as‐synthesized ZnSe nanowires have the single‐crystal hexagonal wurtzite structure with the [001] growth direction. The surface chemical composition of ZnSe nanowires has been studied by X‐ray photoelectron spectroscopy. The cooperative action of the mixed solvents may be responsible for the formation of the morphology of the resulting products. Room‐temperature photoluminescence measurements indicate the as‐grown ZnSe nanostructures have a strong emission peak centered at 587 nm and two weak emission peaks centered at 435 and 462 nm. The strong emission from the ZnSe nanostructures reveals their potential as building blocks for optoelectronic devices.     

Hybrid semiconductor electrodes for light-driven photoelectrochemical switches

Hybrid (n-/p-type) semiconductor electrodes represent a viable strategy for fabrication of wavelength-controlled optoelectronic switches. Four hybrid electrodes (BiVO₄/Co₃O₄, BiVO₄/CuO, TiO₂/Co₃O₄, TiO₂/CuO) were prepared in the form of random assemblies of nanocrystalline powders on ITO-glass and the wavelength dependence of their photocurrent response was investigated. The former three electrodes exhibited wavelength-controlled switching of photocurrent direction, whereas the latter one showed exclusively cathodic photocurrents. The prerequisite for the switching effect is that the potentials of the valence and conduction band edges of an n-type component are more positive than those of a p-type one. Further key parameters influencing the photocurrent response are the applied potential and the presence of electron and hole scavengers.     

Increasing the accuracy of level-based volume detection of medical liquids in test tubes by including the optical effect of the meniscus

A novel system for liquid volume detection is reported in this paper. The system uses two lasers with different wavelengths to scan the entire height of tubes. By detecting the shape and position of the meniscus that is formed at the liquid-air interface, the volume of liquid in a tube of known geometry can be determined. To increase the accuracy of this level-based volume detection, the shape of the meniscus must be considered. The optical effect of the meniscus in such a system was modeled and its effect on the volume detection simulated. A laboratory prototype was built and the biggest difference between the measured power of the transmitted light through the meniscus and the simulated data was less than 8%.     

n-Type Doping of Vapor–Liquid–Solid Grown GaAs Nanowires

In this letter, n-type doping of GaAs nanowires grown by metal–organic vapor phase epitaxy in the vapor–liquid–solid growth mode on (111)B GaAs substrates is reported. A low growth temperature of 400°C is adjusted in order to exclude shell growth. The impact of doping precursors on the morphology of GaAs nanowires was investigated. Tetraethyl tin as doping precursor enables heavily n-type doped GaAs nanowires in a relatively small process window while no doping effect could be found for ditertiarybutylsilane. Electrical measurements carried out on single nanowires reveal an axially non-uniform doping profile. Within a number of wires from the same run, the donor concentrations N _D of GaAs nanowires are found to vary from 7 × 10¹⁷ cm^-3 to 2 × 10¹⁸ cm^-3. The n-type conductivity is proven by the transfer characteristics of fabricated nanowire metal–insulator-semiconductor field-effect transistor devices.     

ESD issues in compound semiconductor high-frequency devices and circuits

The need of ESD protection for high frequency devices and circuits is underlined by reviewing the compound semiconductor material properties with emphasis on ESD stress and by collecting their ESD failure thresholds. Basic requirements for possible ESD protection structures in the microwave frequency regime are discussed and possible ESD protection devices and circuit concepts are proposed.     

掺杂超晶格及其应用前景

掺杂超晶格的层内载流子浓度、有效带隙、二维子带结构和载流子寿命可以用光或外加电势来调制。这导致了掺杂超晶格的电导率、吸收系数、光增益以及发光光谱的光、电可调性。此外,长的载流子复合寿命亦导致了低激发功率下大的光学非线性。这都意味着有可能利用掺杂超晶格制作新型的光电子器件。