3D optical vortices generated by micro-optical elements and its novel applications

In this paper we report on recent development in the areas of optical vortices generated by micro-optical elements and applications of optical vortices, including optical manipulation, radial polarization and secure free space optical communication

Theoretical Study on First Hyperpolarizabilities of End-Capped Triply Branched Dendrimers

A series of end-capped triply branched dendritic chromophores have been studied by means of density functional theory calculations. It is found that the second order nonlinear optical properties of the end-capped dendrimers are strongly dependent on the mutual orientations of the three chromophores, numbers of caps and the conjugation length of the ehromophores. Large enhancement of the first hyperpolarizability can be obtained when dipole moments of three branches in the dendrimers are highly parallelized.

A new scheme of implementing all-optical logic systems exploiting material nonlinearity and polarization based encoding technique

In this letter,the authors propose a new concept of implementing all-optical logic gates by representing the logic states with polarization of an optical signal .As the state of polarization of the light signal is very much suitable for encoding and detecting the bits of data of a digital signal in communication,the scheme may extend some wide applications in all-optical parallel computation and information processing.

Linear Polarization Components of Scattered 90°

A comparison is made of the intensity distribution of the horizontally and vertically polarized radiation sidescattered from small spherical particles in a cylindrical scattering volume.The incident radiation is a nearly collimated linearly polarized He-Ne laser beam.The scattering medium consists of various concentrations of particles which are either 0.22 μm or 0.494 μm in diameter and which were suspended in filtered,distilled water.In general,the effect of the diameter of the particle on depolari-zing the incident beam is more important than the particle concentration,detector depth,and so on.

Preparation of hierarchical CuO@TiO_2 nanowire film and its application in photoelectrochemical water splitting

A new kind of self-standing CuO@TiO2 nanowires (NWs) film with hierarchical feature was prepared by a three-step protocol consisting of hydrothermal reaction, electroless plating, and branched growth processes. This heterostructured CuO@TiO2 NWs film demonstrates the favorable physical properties in the photoelectrochemical cell (PEC) water splitting, such as the hierarchical surface, the extended optical absorption range, and the rapid interface charge transfer kinetics. Under the illumination of the simulated solar light, the pristine TiO2 NWs film only attains a photocurrent density of 0.12 mA/cm2 at 1.0 V versus reversible hydrogen electrode (RHE). Significantly, the CuO@TiO2 NWs film can yield a dramatically increased photocurrent density of 0.56 mA/cm2 at the same applied voltage. Furthermore, amperometric I?t tests of the CuO@TiO2 NWs film reveal satisfactory stability. All the above characteristics of this heterostructured CuO@TiO2 NWs film indicate its great potential in the water splitting applications with solar visible light.

SUSY QCD Impact on Top-Pair Production Associated with a Z^0-Boson at a Photon-Photon Collider

The top-pair production in association with a Z^0-boson at a photon-photon collider is an important process in probing the coupling between top-quarks and vector boson and discovering the signature of possible new physics. We describe the impact of the complete supersymmetric QCD （SQCD） next-to-leading order （NLO） radiative corrections on this process at a polarized or unpolarized photon collider, and make a comparison between the effects of the SQCD and the standard model （SM） QCD. We investigate the dependence of the lowest-order （LO） and QCD NLO corrected cross sections in both the SM and minimal supersymmetric standard model （MSSM） on colliding energy √s in different polarized photon collision modes. The LO, SM NLO, and SQCD NLO corrected distributions of the invariant mass of tt^--pair and the transverse momenta of final Z^0-boson are presented. Our numerical results show that the pure SQCD effects in γγ →tt^- Z^0 process can be more significant in the ＋＋ polarized photon collision mode than in other collision modes, and the relative SQCD radiative correction in unpolarized photon collision mode varies from 32.09% to -1.89% when √s goes up from 500 GeV to 1.5 TeV.

Phonon States and Dispersive Spectra of Polar Optical Phonons in Quasi-One-Dimensional Nanowires of Wurtzite ZnO and Zinc-Blend MgO Semiconductors

Within the framework of the macroscopic dielectric continuum model and Loudon＇s uniaxial crystal model, the phonon modes of a wurtzite/zinc-blende one-dimensional （1D） cylindrical nanowire （NW） are derived and studied. The analytical phonon states of phonon modes are given. It is found that there exist two types of polar phonon modes, i.e. interface optical （IO） phonon modes and the quasi-confined （QC） phonon modes existing in 1D wurtzite/zinc-blende NWs. Via the standard procedure of field quantization, the Fr6hlich electron-phonon interaction Hamiltonians are obtained. Numerical calculations of dispersive behavior of these phonon modes on a wurtzite/zinc-blende ZnO/MgO NW are performed. The frequency ranges of the IO and QC phonon modes of the ZnO/MgO NWs are analyzed and discussed. It is found that the IO modes only exist in one frequency range, while QC modes may appear in three frequency ranges. The dispersive properties of the IO and QC modes on the free wave-number kz and the azimuthal quantum number m are discussed. The analytical Hamiltonians of electron-phonon interaction obtained here are quite useful for further investigating phonon influence on optoelectronics properties of wurtzite/zinc-blende 1D NW structures.

GaAs/AlGaAs heterostructure nanowires studied by cathodoluminescence

In this report we explore the structural and optical properties of GaAs/A1GaAs heterostructure nanowires grown by metalorganic vapour phase epitaxy using gold seed-particles. The optical studies were done by low-temperature cathodo- luminescence （CL） in a scanning electron microscope （SEM）. We perform a systematic investigation of how the nanowire growth-temperature affects the total photon emission, and variations in the emission energy and intensity along the length of the nanowires. The morphology and crystal structures of the nanowires were investigated using SEM and transmission electron microscopy （TEM）. In order to correlate specific photon emission characteristics with variations in the nanowire crystal structure directly, TEM and spatially resolved CL measurements were performed on the same individual nanowires. We found that the main emission energy was located at around 1.48 eV, and that the emission intensity was greatly enhanced when increasing the GaAs nanowire core growth temperature. The data strongly suggests that this emission energy is related to rotational twins in the GaAs nanowire core. Our measurements also show that radial overgrowth by GaAs on the GaAs nanowire core can have a deteriorating effect on the optical quality of the nanowires. Finally, we conclude that an in situ pre-growth annealing step at a sufficiently high temperature significantly improves the optical quality of the nanowires.

Wavelength conversion based on nonlinear polarization rotation in gain transparent SOA

We describe an all-optical wavelength conversion scheme for 1310 nm to 1550 nm based on nonlinear polarization rotation in a gain-transparent semiconductor optical amplifier （GT-SOA） which brings in the assistant light to improve the property of the converted light. From the SOA carder density equations, the 1310 nm-to-1550 nm wavelength conversion scheme is analyzed by the Jones matrix. The phase shift between TE and TM modes and the converted light are simulated at bit rate of 30 Gbit/s. We also analyze the influence of the input signal power, the injected current and the assistant light power on the extinction ratio of the converted li~,ht.