Control of polarization signal distortion by frequency domain phase conjugation in optical fiber systems

Optical frequency domain phase conjugation (FDPC) is based on phase conjugation of spectrum of an input signal. It is equivalent to the phase conjugation and the time reversal of the temporal envelope of an input signal. The use of FDPC to control polarization signal distortion in birefringent optical fiber systems is proposed. Evolution of polarization signals in the system using midway FDPC is analyzed theoretically and simulated numerically. It is shown that the distortion of polarization signals can be controlled effectively by FDPC. The impairments due to dispersion and nonlinear effects can be suppressed simultaneously.

Smoothing effect in the broadband laser through a dispersive wedge

The propagation expression of a broadband laser passing through a dispersive wedge is derived on the basis of the Huygens-Fresnel diffraction integral, Smoothing effects caused by the phase perturbation of the dispersive wedge on the intensity profiles are investigated in detail. The phase perturbation of the dispersive wedge induces a relative transverse position shift between the diffraction patterns of different frequency components. The relative transverse position shift is of great benefit to the fill of the intensity peaks of some patterns in the valleys of others when these patterns are overlapped and thus the smoothing effect is achieved. (c) 2006 Elsevier B.V. All rights reserved.

Subwavelength imaging by a dielectric-tube photonic crystal

In contrast to previous two-dimensional coated photonic crystals, in this paper we propose a left-handed one that is made of dielectric tubes arranged in a close-packed hexagonal lattice. Without metallic cores, this structure is low-loss and convenient to fabricate. Negative refraction and its resulting focusing are investigated by dispersion characteristic analysis and numerical simulation of the field pattern. With proper modification at the interface, the image is improved. With better isotropy than that with noncircular rods, planoconcave lenses made by dielectric tubes focus a Gaussian beam exactly at R//n - 1/.

Subwavelength imaging with two symmetrical interfaces by dielectric-tube photonic crystals

As distinct from coated photonic crystals, in this paper we propose a novel one that is made of dielectric tubes arranged in a close-packet square lattice. Without metallic cores, this structure is low-loss and convenient to fabricate. A left-handed frequency region is found in the second band by dispersion characteristic analysis. Without inactive modes for the transverse electric mode, negative refraction and subwavelength imaging are demonstrated by the finite-difference time-domain simulations with two symmetrical interfaces, i.e. Gamma X and Gamma M.

Preparation, characterization and gas sensing properties of high soluble metal (II) phthalocyanine thin films by spin-coating method

Three novel metal (II) phthalocyanine complexes were synthesized by cyclic tetramerisation reaction of a dicyano benzene component and different metal ions (Pd2+, Co2+, Zn2+). The structure of complexes was confirmed by elemental analysis, mass and IR spectrum. The excellent solubility of the complexes in benzene enabled us to obtain films by a spin-coating method. The films were characterized by IR, electronic spectral and AFM. The gas sensing properties to NO2 of the metal (II) phthalocyanine complex films were studied. In addition, the effects of different metal ions and the gas sensing temperature on the sensing properties were studied. (C) 2005 Elsevier B.V. All rights reserved.

Synthesis, spectral, and thermal characterizations of Ni(II) and Cu(II) beta-diketone complexes with thenoyltrifluoroacetone ligand

Two kinds of nickel(II) and copper(II) P-diketone complexes derived from thenoyltrifluoroacetone ligand with blue-violet light absorption were synthesized by reacting free ligand and different metal(II) ions in sodium methoxide solution. Their structures were postulated based on elemental analysis, ESI-MS, FT-IR spectra and UV-vis electronic absorption spectra. Smooth films on K9 glass substrates were prepared using the spin-coating method. Their solubility in organic solvents, absorption properties of thin film and thermal stability of these complexes were evaluated. (c) 2006 Elsevier B.V. All rights reserved.

Nickel(II) and copper(II) complexes containing 2-(2-(5-substitued isoxazol-3-yl)hydrazono)-5,5-dimethylcyclohexane-1,3-dione ligands: Synthesis, spectral and thermal characterizations

Two new hydrazone chelating ligands, 2-(2-(5-methylisoxazol-3-yl)hydrazono)-5,5-dimethylcyclohexane-1,3-dione (HL1) and 2-(2-(5-tert-butylisoxazol-3-yl)hydrazono)-5,5-dimethylcyclohexane- 1,3-dione (HL2), and their nickel(II) and copper(II) complexes were synthesized using the procedure of diazotization, coupling and metallization. Their structures were postulated based on elemental analysis, H-1 NMR, ESI-MS, FT-IR spectra and UV-vis electronic absorption spectra. Smooth films of these complexes on K9 glass substrates were prepared using spin-coating and their absorption properties were evaluated. The thermal properties of the metal(II) complexes were investigated by thermogravimetry (TG) and differential thermogravimetry (DTG). Different thermodynamic and kinetic parameters namely activation energy (E

Optical properties of dye-doped zirconia films by spectroscopic ellipsometry

The optical properties of zirconia films doped with rhodamine 6G and oxazine 725 by the sol-gel process were investigated using spectroscopic ellipsometry (SE). Accurate refractive index n and the extinction coefficient k were determined using a three-oscillator classical Lorentz model in the wavelength range of 300-800 nm. The derived refractive index of dye-doped films exhibited anomalous dispersion in the absorption region. Wavelength tunable output lasing action yellow and near-infrared wavelength region was achieved by DFB configuration using zirconia films doped with R6G and oxazine 725. (c) 2006 Elsevier B.V. All rights reserved.

Beam conditions for radiation generated by an electromagnetic J 0-correlated Schell-model source

Based on the 2 x 2 (electric field) cross-spectral density matrix, a model for an electromagnetic J(0)-correlated Schell-model beam is given that is a generalization of the scalar J(0)-correlated Schell-model beam. The conditions that the matrix for the source to generate an electromagnetic J(0)-correlated Schell-model beam are obtained. The condition for the source to generate a scalar J(0)-correlated Schell-model beam can be considered as a special case. (C) 2008 Optical Society of America

Thermal analyses, spectral characterization and structural interpretation of Yb3+ doped TeO2-ZnO-ZnCl2 glasses

Bulk-lasses have been prepared in the TeO2-ZnO-ZnCl2 systems. Their characteristic temperatures were determined and analyzed. Raman and FT-IR spectra were used to analyze the effect of ZnCl2 on the structure and spectral properties of tellurite glasses and OH- groups in this glass system. The spectroscopic properties including absorption spectra, emission cross-sections and fluorescence lifetimes of Yb3+ in TeO2-ZnO-ZnCl2 were measured and calculated. It is demonstrated that the progressive replacement less than 20 mol% of TeO2 by ZnCl2 improves the thermal stability, removes the OH- groups, turns TeO4 bipyramidal arrangement into TeO3 (and/or TeO3+1) trigonal pyramids structures and results in the decrease of the symmetry of the structure, which increases the emission cross-sections and lifetimes. But when the content of ZnCl2 up to 30 mol%, the glass system becomes more hygroscopic and introduces more OH- groups, which decrease the emission cross-sections and shorten the lifetimes. The results show that the glass system with (TeO2)-Te-69-(ZnO)-Zn-10-20ZnCl(2)-1Yb(2)O(3) is a desirable component for active laser media for high power generation. (c) 2005 Elsevier B.V. All rights reserved.

Spectral properties and stability of Er3+-doped TeO2-WO3 glass

Er3+-doped TeO2-WO3 glass was fabricated and characterized by absorption spectrum, fluorescence spectrum, Raman spectrum and stability. The Judd-Ofelt parameter ohm(t)(t = 2, 4, 6) were calculated from the absorption spectrum by the Judd-Ofelt theory. The fluorescence spectrum indicates that the fluorescence width at half-maximum (FWHM) is 66nm. The stimulated emission cross-section of Er3+ in TeO2-WO3 glass at 1532 nm was calculated to be 0.80 x 10(-20) cm(2) by McCumber theory. The phonon energy of TeO2-WO3 glass is found to be 931 cm(-1). The difference between crystallization onset temperature and glass transition temperature Delta T is 112 degrees C. These results show that Er3+-doped TeO2-WO3 glass has higher stability and good spectral properties, which were useful for broadband amplifier. (c) 2005 Elsevier B.V. All rights reserved.

Effects of Yb ion concentration on the spectral properties of lead silica glasses

The spectral properties in different concentration of Yb ions (0.5-5 mol%)-doped silica glasses are explored in this paper. The glasses are prepared by traditional melting method. The absorption spectra and the fluorescent lifetime (tau(f)) are measured at room temperature and low temperature (18 K). The stimulated cross-section (sigma(emi)) and potential laser properties (beta(min), I-sat, I-min) are calculated based on the absorption spectra. The absorption cross-section (sigma(abs)) are in the range 1.08 x 10(-20) - 1.18 x 10(-20) cm(2) in different glasses, the fluorescence lifetime (tau(f)) change from 1.9 to 1.2 ms with the increase of Yb3+ concentration. The potential laser properties indicate that lead silica glass is a good host for highly Yb ion doping glass. (c) 2005 Elsevier B.V. All rights reserved.

Fluorescence lifetime increase by introduction of F- ions in ytterbium-doped TeO2-based glasses

this paper was retracted

Blue green emission from a Cu+-Doped transparent material prepared by sintering porous glass

A colorless transparent, blue green emission material was fabricated by sintering porous glass impregnated with copper ions. The emission spectral profile obtained from Cu+ -doped high silica glass (HSG) by 267-mn monochromatic light excitation matches that obtained by pumping with an 800-nm femtosecond laser, indicating that the emissions in both cases come from an identical origin. The upconversion emission excited by 800-nm femtosecond laser is considered to be a three-photon excitation process. A tentative scheme of upconverted emission from Cu+ -doped HSG was also proposed. The glass materials presented herein are expected to find application in lamps, high density optical storage, and three-dimensional color displays.

Growth and spectral characterization of beta-Ga2O3 single crystals

Beta gallium oxide (beta-Ga2O3) single crystals were grown by the floating zone technique. The absorption spectra and the luminescence of the crystals were measured. The absorption spectra showed an intrinsic short cutoff edge around 260 nm with two shoulders at 270 and 300 nm. Not only the characteristic UV (395 nm), blue (471 nm) and green (559 nm) lights, but also the red (692 nm) light can be seen in the emission spectra. The deep UV light was attributed to the existing of quantum wells above the valence band and the red light was owed to the electron-hole recombination via the vicinity donors and acceptors. (c) 2006 Elsevier Ltd. All rights reserved.