Sep 2010, Volume 3 Issue 3
    

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  • Research articles
    Fully transparent flexible transistors built on metal oxide nanowires
    Di CHEN, Guozhen SHEN, Jing XU,
    2010, 3(3): 217-227. https://doi.org/10.1007/s12200-010-0110-0
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    Transparent electronics has attracted great research efforts in recent years due to its potential to make significant impact in many area, such as next generation displays, ultraviolet (UV) detectors, solar cells, charge-coupled devices (CCDs), and so on. Central to the realization of transparent electronics is the development of high performance fully transparent thin-film transistors (TFTs). One-dimensional (1-D) nanostructures have been the focus of current researches due to their unique physical properties and potential applications in nanoscale elec-tronics and optoelectronics. Among 1-D nanostructures, transparent metal oxide nanowires are one of the best candidates to make fully transparent TFTs. We provide in this paper the most recent development on the fabrication of fully transparent TFT using metal oxide nanowires as the device elements. First, the review article gives a general introduction about the development of transparent elec-tronics using different kinds of materials as the devices elements, including organic semiconductors, metal oxide thin films, and metal oxide nanowires. Second, the growth of metal oxide nanowires using vapor phase methods governed by two different growth mechanisms: vapor-solid mechanism and vapor-liquid-solid mechanism, respectively, are described. Third, the fabrication of transparent and flexible TFTs using different metal oxides nanowires is comprehensively described. In conclusion, the challenges and prospects for the future are discussed.
  • Research articles
    Bis-(8-hydroxyquinoline) mercury nanoribbons: preparation, characterization and photoconductivity
    Li LIU, Mingwang SHAO, Xiuhua WANG,
    2010, 3(3): 228-231. https://doi.org/10.1007/s12200-010-0113-x
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    Bis-(8-hydroxyquinoline) mercury nanoribbons with average width of 300 nm, thickness of 50 nm and length of up to tens of micrometers were synthesized by a facile solvothermal method. X-ray powder diffraction and Fourier transform infrared spectrum were employed to determine their structure. The conductivity of a bundle of nanoribbons was also measured, which exhibited linear current-voltage characteristics and excellent photoresponse to light, indicating their potential applications in photoswitch nano-devices in the future.
  • Research articles
    Circuit modeling of quantum dot semiconductor optical amplifier
    Yi YU, Lirong HUANG, Meng XIONG, Dexiu HUANG,
    2010, 3(3): 232-240. https://doi.org/10.1007/s12200-010-0101-1
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    A circuit model of a quantum dot semiconductor optical amplifier is proposed by employing standard rate equations. Using this model, the saturation property and dynamic performance of the quantum dot semiconductor optical amplifier are analyzed by PSPICE simulation. We also investigate wavelength conversion based on cross-gain modulation for the quantum dot semiconductor optical amplifier. The corresponding results are in agreement with the previous published works.
  • Research articles
    InAs/GaAs quantum dots grown on different GaAs substrates with graded In x Ga 1? x As strain-reducing layer
    Shuping FEI, Zhongwei SHI, Lirong HUANG,
    2010, 3(3): 241-244. https://doi.org/10.1007/s12200-010-0109-6
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    Self-assembled InAs quantum dots with graded composition strain-reducing layer (SRL) grown on exact substrates were studied. It is shown that a graded InxGa1−xAs SRL leads to growth quality improvement, emission efficiency enhancement, and wavelength blueshift. Samples grown on 2° misoriented substrates with different In contents in graded InxGa1−xAs SRL were also investigated, and emission efficiency enhancement and wavelength blueshift were found when graded SRL was introduced and when the change rate of In content in graded InxGa1−xAs SRL was enlarged.
  • Research articles
    High-speed, all-optical XOR gates using semiconductor optical amplifiers in ultrafast nonlinear interferometers
    Xuelin YANG, Qiwei WENG, Weisheng HU,
    2010, 3(3): 245-252. https://doi.org/10.1007/s12200-010-0105-x
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    We will review three recently-proposed high-speed, all-optical Exclusive OR (XOR) gates operating at 40 and 85 Gb/s, which were demonstrated using ultrafast nonlinear interferometers (UNIs) incorporating semiconductor optical amplifiers (SOAs). The first 40-Gb/s XOR gate was obtained using a dual UNI configuration. The second is a 40-Gb/s XOR gate without additional probe beam required, where the only inputs launched into the setup were data A and B. The XOR logic of data A and B is the sum of two components "Graphic" and "Graphic", each of which was obtained from the output of UNI via cross-phase modulation (XPM) in SOAs. Furthermore, an 85-Gb/s XOR gate is, by far, the fastest XOR gate realized by SOAs, which was also demonstrated using a dual UNI structure. The operating speed of the XOR gate was enhanced by incorporating the recently proposed turbo-switch configuration. In addition, the SOA switching pulse energies of these XOR gates were lower than 100fJ.
  • Research articles
    Experimental investigation into conversion efficiency of cascading four-wave mixing
    Liang ZHAO, Junqiang SUN,
    2010, 3(3): 253-259. https://doi.org/10.1007/s12200-010-0107-8
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    We have proposed and experimentally demonstrated a scheme for cascading four-wave mixing (CFWM) by exploiting nonlinearity in highly nonlinear fiber (HNLF). Through utilizing optical spectrum analyzer (OSA), the second-order sideband products are observed in our experiment by only launching two waves into HNLF, and the conversion efficiency from the injected wave to each sideband is discussed in detail. It is found that only the conversion efficiency of the satellite wave will be increased with the power of the tunable injected wave when the power and the wavelength of the other one are fixed. Furthermore, the conversion efficiency of all the sidebands will be decreased with the absolute value of detune of injected wavelengths increasing. Also, the authors have demonstrated that the power of the satellite wave will be influenced most among all the sidebands if tuning the injected wave power. The proposed scheme can find potential applications in parametric amplification, frequency conversion, and optical quantum-information processing.
  • Research articles
    Investigation on Brillouin scattering characteristics in photonic crystal fibers
    Yuan LI, Yange LIU, Junfa ZHAO, Boyin TAI, Aidong YAN,
    2010, 3(3): 260-263. https://doi.org/10.1007/s12200-010-0098-5
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    Brillouin scattering characteristics of photonic crystal fibers (PCFs) are investigated theoretically and experimentally in this paper. The results of two kinds of PCFs are compared and discussed, the influences of size of fiber core on the acoustic modes and hence on the Brillouin resonance peaks are explained. Furthermore, the improvement for our research is also presented.
  • Research articles
    Use of adaptive RLS, LMS, and NLMS algorithms for nonlinearity modeling in a modified laser interferometer
    Saeed OLYAEE, Mohammad Shams Esfand ABADI, Samaneh HAMEDI, Fatemeh FINIZADEH,
    2010, 3(3): 264-269. https://doi.org/10.1007/s12200-010-0095-8
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    Laser heterodyne interferometer is one kind of nano-metrology systems which has been widely used in industry for high-accuracy displacement measurements. The accuracy of the nano-metrology systems based on the laser heterodyne interferometers can be effectively limited by the periodic nonlinearity. In this paper, we present the nonlinearity modeling of the nano-metrology interferometric system using some adaptive filters. The adaptive algorithms consist of the least mean squares (LMS), normalized least mean squares (NLMS), and recursive least squares (RLS). It is shown that the RLS algorithm can obtain optimal modeling parameters of nonlinearity.
  • Research articles
    Theoretical demonstration for signal gain in multiple four-wave mixing processes based on cubic susceptibility medium
    Liang ZHAO, Junqiang SUN, Zhefeng HU, Qian HU, Yujie ZHOU, Jing SHAO, Tianye HUANG, Jun LI,
    2010, 3(3): 270-282. https://doi.org/10.1007/s12200-010-0106-9
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    An insight into the signal gain in multiple four-wave mixing (MFWM) processes based on a cubic susceptibility medium is theoretically proposed and demonstrated. A dual-pumped fiber optical parametric amplification (FOPA) model is developed with the exact expressions for the signal gain and its 3-dB bandwidth successfully yielded. With these analytical expressions, we show that when pump-1 and pump-2 wavelengths tuned at 1549 and 1551.02 nm, the 3-dB bandwidth of the signal gain can be achieved at about 2253.4 nm theoretically by properly setting the pumped powers. Numerical simulations show that there is a small pinnacle emerging in the signal gain spectrum owing to the degenerate OPA process occurring. The proposed OPA model can find potential applications in all-optical wavelength conversion, optical amplifier, and all-optical sampling.
  • Research articles
    Switchable-multi-wavelength fiber laser based on dual-core all-solid photonic bandgap fiber
    Jiaqi ZHAO, Zhi WANG, Yange LIU, Bo LIU,
    2010, 3(3): 283-288. https://doi.org/10.1007/s12200-010-0099-4
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    In this paper, we propose and demonstrate a switchable multi-wavelength fiber laser based on a dual-core all-solid photonic bandgap fiber (PBGF) comb-like filter. The transmission properties of the dual-core all-solid PBGF are theoretically and experimentally investigated. Then the fiber ring laser based on the PBGF is realized and its wavelength-selective mechanisms are studied. By adjusting the polarization controller (PC), the number and location of the laser wavelength can be tunable.
  • Research articles
    Deep notch filter based on liquid-filled photonic crystal fiber
    Bing ZOU, Yange LIU, Zhi WANG, Bo LIU,
    2010, 3(3): 289-291. https://doi.org/10.1007/s12200-010-0100-2
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    A deep notch filter in a liquid-filled photonic bandgap fiber (PBGF) realized via filling an erbium-doped solid core photonic crystal fiber with high-index liquid is proposed and demonstrated. The numerical investigation indicates that the notch is formed due to avoid-crossing effect between the fundamental mode and LP02 supermodes. The resonance wavelength of the filter can be tuned by adjusting the temperature of the liquid-filled PBGF and shifts toward short wavelength. The blue-shift speed average is 1.3 nm/°C.
  • Research articles
    Diffraction of Lorentz-Gauss beam in uniaxial crystals: orthogonal to optical axis
    Jia LI, Yanru CHEN, Shixue XU, Yongqing WANG, Muchun ZHOU, Qi ZHAO, Yu XIN, Feinan CHEN,
    2010, 3(3): 292-302. https://doi.org/10.1007/s12200-010-0111-z
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    Based on the diffraction theory of beams in uniaxial crystals, diffraction properties of a Lorentz-Gauss beam in uniaxial crystals orthogonal to the optical axis are derived in analytical forms. Diffraction fields, intensity distributions and effects of beam parameters are investigated by numerical examples, respectively. Results show that, upon propagation, initial field components and intensity distributions of Lorentz-Gauss beams would deteriorate due to effects of anisotropic media. When the Lorentz-Gauss beam diffracts into the far field, its intensity distribution would convert into a four-petal profile. Beam parameters wx and wy are shown to have a strong influence on intensity distributions. By selecting different values of them, profiles of Lorentz-Gauss beams would be different upon propagation.
  • Research articles
    Laser stripping of fiber Bragg grating polymer coating using pulsed 10.6?μm TEA CO 2 laser
    Haihong ZHU, Wenjuan LEI, Cheng DAI, Zuhai CHENG,
    2010, 3(3): 303-307. https://doi.org/10.1007/s12200-010-0097-6
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    Stripping the polymer coating is the first step for the fabrication of fiber Bragg grating (FBG). The conventional stripping approaches are labor intensive and time consuming. Because of high precision and throughput, as well as non-contacting, laser stripping obtained more and more attention in recent years. This paper reports the primary experiments on laser stripping of polymer coating from FBG using pulsed transverse electric atmospheric (TEA) CO2 laser with wavelength of 10.6 μm and pulse width of 2 μs. Using cylindrical lenses, the coating can be removed thoroughly at one time. The theoretical analysis and experimental investigations were carried out. The influence of laser fluence and pulse number on stripping quality has been investigated. Scanning electron microscopy (SEM), optical microscope, and electrical balance were employed to detect the quality removal. The result shows that excellent quality removal is possible by using pulsed 10.6 μm TEA CO2 laser.
  • Research articles
    Optimization for data de-duplication algorithm based on file content
    Xuejun NIE, Leihua QIN, Jingli ZHOU, Ke LIU, Jianfeng ZHU, Yu WANG,
    2010, 3(3): 308-316. https://doi.org/10.1007/s12200-010-0103-z
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    Content defined chunking (CDC) is a prevalent data de-duplication algorithm for removing redundant data segments in archival storage systems. Current researches on CDC do not consider the unique content characteristic of different file types, and they determine chunk boundaries in a random way and apply a single strategy for all file types. It has been proven that such method cannot achieve optimal performance for compound archival data. We analyze the content characteristic of different file types and propose candidate anchor histogram (CAH) to capture it. We propose an improved strategy for determining chunk boundaries based on CAH and tune some key parameters of CDC based on the data layout of underlying data de-duplication file system (TriDFS), which can efficiently store variable-sized chunks on fixed-sized physical blocks. These strategies are evaluated with representative archival data, and the result indicates that they can increase on average the compression ratio by 16.3% and write throughput by 13.7%, while only decrease the read throughput by 2.5%.
  • Research articles
    Tunable wettability of metallic films with assistance of porous anodic aluminum oxide
    Dongdong LI, Chuanhai JIANG, Xin REN, Jiankun ZHOU,
    2010, 3(3): 317-320. https://doi.org/10.1007/s12200-010-0104-y
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    The present work demonstrates a simple method to prepare nanostructured Ni films with different morphologies with the assistance of porous anodic aluminum oxide (AAO) membranes. A great distinction is observed as the Ni films deposited onto the top and bottom sides of AAO membranes. The wetting properties of as-prepared membranes are investigated by measuring the contact angles of water on the surfaces. Results show that the static water contact angle changes dramatically from 124°±1° to 45°±1° on different Ni films, implying a change of the wettability from hydrophobicity to hydrophilicity affected by the surface patterns. This versatile approach can be conducted on various materials with potential applications in a broad range of fields.
  • Research articles
    Investigation of Al Schottky junction on n-type CdS film deposited on polymer substrate
    Sandhya GUPTA, Dinesh PATIDAR, Mahesh BABOO, Kananbala SHARMA, N. S. SAXENA,
    2010, 3(3): 321-327. https://doi.org/10.1007/s12200-010-0102-0
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    A systematic study has been made on the behavior of Al/n-CdS thin film junction on flexible polymer substrate (polyethylene terephthalate, PET) grown using thermal evaporation method. Temperature dependence of I−V measurements for this junction has been done which closely follow the equations of Schottky barrier junction dominated by thermionic emission mechanism. Intrinsic and contact properties such as barrier height, ideality factor and series resistance have been calculated from I−V characteristics. The barrier height of Al/n-CdS junction is found to increase with increase in temperature whereas ideality factor and series resistance decrease with increase in temperature.
  • Research articles
    Aged rare earth doped silicates as optoelectronic material
    Vandana RANGA, H. N. ACHARYA, R. K. KHANNA, Anirudh KUMAR,
    2010, 3(3): 328-331. https://doi.org/10.1007/s12200-010-0096-7
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    Samples of various concentrations were prepared and kept unsintered for a period of three years to study the consistency of composition prepared and structural evolution of glass. The expanded peaks in the Raman spectra arise due to thermal agitation, and a Boltzmann type of distribution was expected in the silicate gels. The behavior of the gels during the dehydroxylation and dehydration is conditioned by its microstructure, which depends upon the physical conditions, i.e., pH, and drying conditions.