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Pb-doped tetrahedrite Cu12-xPbxSb4S13 (x = 0, 0.25, 0.50, 0.75, 1.00, 1.25 and 1.50) samples were prepared and their thermoelectric properties were investigated in the temperature range from 300 K to 723 K. The results show that Pb is successfully doped in Cu(1) site, which brings about both 10–118% increase in Seebeck coefficient owing to the decrease of hole concentration and 87–168% decrease in thermal conductivity due to the enhanced phonon scattering by the dopant atoms. As a result, a maximum ZT = 0.8 at 723 K is achieved for Cu11PbSb4S13, which is ∼43% larger than that of pristine Cu12Sb4S13. Present results demonstrate that Pb is an effective dopant to elevate thermoelectric performance of Cu12Sb4S13.

A novel amphiphilic copolymer, poly (ethylene glycol)-graft-polyethyleneimine/amide (PEG-g-PEI/amide), is synthesized by grafting PEG and1,2-cis-Cyclohexanedicarboxylic anhydride onto the PEI. PEGylated polymeric micelles can be assembled from the amphiphilic copolymers with well-defined nano-sizes, and anti-cancer drugs are successfully loaded into micelle core formed by the amide. The amides with neighboring carboxylic acid groups exhibit pH-dependent hydrolysis and can reversibly shield the cationic charge of amine groups on the PEI, giving the micelles a charge-conversion property from negative to positive in acidic tumor tissue environment. Meanwhile, the cleavage of amide bonds at acidic pH also results in the disassembly of the micelle and pH-responsive drug release. These micelles are promising drug delivery systems due to their smart properties: PEGylation, suitable size, charge-conversion, and simultaneous pH-sensitive drug release.

A novel comb-like derivative CPEG-g-DNQ was prepared by incorporating light responsive 2-diazo-1,2-naphthoquinone (DNQ) groups into the structure of comb-like poly(ethylene glycol) (CPEG). DLS and TEM results showed that CPEG-g-DNQ self-assembled into spherical micelles with an average size of about 135 nm in water. Upon exposure to light, the micelles could be disrupted because of the conversion of hydrophobic DNQ to hydrophilic 3-indenecarboylic acid. Additionally, hydrophobic coumarin 102 was successfully loaded into the micelles and photo-induced ON-OFF release was demonstrated by fluorescence spectroscopy. MTT assay revealed that the micelles are biocompatible. These photo-responsive micelles might have great potential for controlled release of hydrophobic drugs.

The femtosecond laser induced void array inside Al2O3 crystals was discussed. The void array was formed spontaneously under the irradiation of a single beam of infrared femtosecond laser which was focused at a fixed point inside the Al2O3 crystal sample. It was found that the regular voids only could be fabricated near the sample surface, which was different from the situation in CaF2 single crystal reported before. The possible mechanism of the phenomena was also discussed.

In clustering analysis of remote sensing imagery, a commonly held assumption is that the feature space can be modelled as a mixture of Gaussians. However, the assumption is not true for many real data and therefore incorrect classification results are often obtained by parametric methods. Nonparametric methods in feature space analysis can avoid the use of the normality assumption. Arbitrarily structured feature spaces can be analysed only by means of nonparametric methods as these methods do not have embedded assumptions. The mean shift is a basic computational module of the nonparametric technique in pattern recognition. The mean shift procedure can be used to cluster multispectral remote sensing imagery. Earlier clustering techniques based on the mean shift used a single scale over the entire feature space and were not feasible for the analysis of complex multimodal feature spaces. In this paper, we present an adaptive mean shift method in which local scale information is involved. The proposed algorithm can find arbitrary density, size and shape clusters in remote sensing imagery. The method is a simple technique of unsupervised image classification. We demonstrate its advantages in classification accuracy over earlier methods described in this paper.

Luminescences from bismuth-doped lime silicate glasses were investigated. Luminescences centered at about 400, 650, and 1300 nm were observed, excited at 280, 532 and 808 nm, respectively. These three luminescence bands arise from three different kinds of bismuth ions in the glasses. The visible luminescences centered at 400 and 650 nm arise from Bi 3+ , and Bi 2+ , respectively. The infrared luminescences cover the wavelength range from 1000 to 1600 nm when exited by an 808 nm laser diode. The full width at half maximum (FWHM) of the infrared luminescences is more than 205 nm. The intensity of the infrared luminescence decreases with the increment in CaO content. We suggest that the infrared luminescences might arise from Bi + . Such broadband luminescences indicate that the glasses may be potential candidate material for

Transparent Ni2+-doped MgO-Al2O3-Ga2O3-SiO2-TiO2 glass ceramics were fabricated. The precipitated nanocrystal phase in the glass ceramics was identified by X-ray diffraction and transmission electron microscope. Broadband near-infrared emission centered at 1220 nm with full width at half maximum of about 240 nm and lifetime of about 250 mu s was observed with 980 nm excitation. The longer wavelength emission compared with Ni2+-doped MgAl2O4 crystal was attributed to the low crystal field occupied by Ni2+ in the glass ceramics. The present Ni2+-doped transparent glass ceramics may have potential applications in broadband optical amplifiers. (c) 2007 Elsevier B.V. All rights reserved.

Transparent Ni2+-doped MgO–Al2O3–SiO2 glass ceramics without and with Ga2O3 were synthetized. The precipitation of spinel nanocrystals, which was identified as solid solutions in the glass ceramics, could be favored by Ga2O3 addition and their sizes were about 7.6 nm in diameter. The luminescent intensity of the Ni2+-doped glass ceramics was largely enhanced by Ga2O3 addition which could mainly be caused by increasing of Ni2+ in the octahedral sites and the reduction of the mean frequency of phonon density of states in the spinel nanocrystals of solid solutions. The full width at half maximum (FWHM) of emissions for the glass ceramics with different Ga2O3 content was all more than 200 nm. The emission lifetime increased with the Ga2O3 content and the longest lifetime is about 250 μs. The Ni2+-doped transparent glass ceramics with Ga2O3 addition have potential application as broadband optical amplifier and laser materials.

Microvoid arrays were self-organized when femtosecond laser beam was tightly focused at a fixed point inside CaF2 crystal sample. Expect the void array grown below the focal point which had been reported before, we found another void array grown vertical to the laser propagation direction. This result has potential application in the fabrication of integrated micro-optic elements and photonic crystals. The possible mechanism of the phenomenon was proposed and verified experimentally.

We report femtosecond laser induced valence state and refractive index change in transparent Sin(3+)-doped fluoroaluminate glass. The effect of annealing on the induced changes was studied and the thermal stability of these changes was discussed. The results show that the femtosecond laser induced valence state change is more stable than the induced refractive index change. The observed phenomenon could be applied to design the thermally erasable or stable storage medium. (c) 2007 Elsevier B.V. All rights reserved.

We report on three-dimensional precipitation of Au nanoparticles in gold ions-doped silicate glasses by a femtosecond laser irradiation and further annealing. Experimental results show that PbO addition plays the double roles of inhibiting hole-trapped centers generation and promoting formation and growth of gold nanoparticles. Additionally, glass containing PbO shows an increased non-linear absorption after femtosecond laser irradiation and annealing. The observed phenomena are significant for applications such as fabrications of three-dimensional multi-colored images inside transparent materials and three-dimensional optical memory, and integrated micro-optical switches. (c) 2007 Elsevier B.V. All rights reserved.

New broadband near infrared luminescence covering the whole work windows (1260-1625 nm) of the current wavelength division multiplexing (WDM) system was found from bismuth-activated M2O-Al2O3-SiO2 (M = Li, Na) and Li2O-Ta2O5-SiO2 glasses at room temperature in the case of 808 nm-laser excitation. But the near infrared luminescence mechanism of the bismuth-activated glasses is not well understood up to now. The figure-of-merits of bandwidth and gain of the glasses are better than those of Er3+-doped silicate glasses and Ti3+ doped sapphire, implying they are the promising gain-medium candidates for the broadband amplifiers and the widely tunable laser sources. (c) 2007 Elsevier B.V. All rights reserved.

Photoluminescence of undoped and B-doped ZnO in silicate glasses was investigated by varying the concentration of ZnO (35–50 mol%) and B dopant (0–10 mol%) in the glass matrices. The broad and intense near band edge emissions were observed while the visible light emission was very weak. UV luminescence in all samples was red-shifted relative to the exciton transition in bulk ZnO and enhanced by decreased ZnO concentration due to higher degree of structural integrity and the lower aggregation degree of ZnO. Donor B dopant played the double roles of filling conduction bands to broaden band gap when its concentration was lower than 5 mol%, and emerging with conduction bands to narrow the gap when B dopant exceeded this value.

Cladding band structure of air-guiding photonic crystal fibers with high air-filling fraction is calculated in terms of fiber shape variation. The fundamental photonic band gap dependence on structure parameters, air-filling fraction and spacing, is also investigated. The numerical results show that the band gap edges shift toward longer wavelength as the air-filling fraction is increased, whereas the relative band gap width increases linearly. For a fixed air-filling fraction, the band gap edges with respect to spacing keep constant. With this method, the simulation results agree well with the reported data.

Broadband infrared luminescence is observed in various Bi-doped oxide glasses prepared by conventional melting-quenching technique. The absorption spectrum of the Bi-doped germanium oxide glass consists of five broad peaks at below 370, 500, 700, 800 and 1000 nm. The fluorescence spectrum exhibits a broad peak at about 1300 nm with full width at half maximum (FWHM) of more than 300 nm when excited by an 808 nm laser diode. The fluorescence lifetime at room temperature decreases with increasing Bi2O3 concentration. Influence of the glass composition and melting atmosphere on the fluorescence lifetime and luminescent intensity is investigated. The mechanism of the broadband infrared luminescence is suggested. The product of stimulated emission cross-section and lifetime of the Bi-doped aluminophosphate glass is about 5.0 X 10(-24) cm(2) s. The glasses might be promising for applications in broadband optical fiber amplifiers and tunable lasers. (c) 2007 Elsevier B.V. All rights reserved.

Broadband near-infrared (IR) luminescence in transparent alkali gallium silicate glass-ceramics containing Ni2+-doped β-Ga2O3 nanocrystals was observed. This broadband emission could be attributed to the 3T2g (3F) → 3A2g (3F) transition of octahedral Ni2+ ions in glass-ceramics. The full width at half-maximum (FWHM) of the near-IR luminescence and fluorescent lifetime of the glass-ceramic doped with 0.10 mol% NiO were 260 nm and ∼1220 μs, respectively. It is expected that transparent Ni2+-doped β-Ga2O3 glass-ceramics with this broad near-IR emission and long fluorescent lifetime have potential applications as super-broadband optical amplification media.

Infrared (IR) luminescence covering 1.1 to ∼1.6 μm wavelength region was observed from bismuth-doped barium silicate glasses, excited by a laser diode at 808 nm wavelength region, at room temperature. The peak of the IR luminescence appears at 1325 nm. A full width half-maximum (FWHM) and the lifetime of the fluorescence is more than 200 nm and 400 μs, respectively. The fluorescence intensity increases with Al2O3 content, but decreases with BaO content. We suggest that the IR luminescence should be ascribed to the low valence state of bismuth Bi2+ or Bi+, and Al3+ ions play an indirect dispersing role for the infrared luminescent centers.

We report a method for the selective introduction of fluorescent Ag nanoclusters in glass. Extinction and photoluminescence spectra show that a fraction of the Ag atoms are generated through femtosecond laser induced multiphoton reduction and then aggregate to form Ag nanoclusters after heat treatment. Red luminescence from the irradiated region is observed under blue or green laser excitation. The fluorescence can be attributed to interband transitions within Ag nanoclusters. This method provides a novel route to fabricate fluorescent nanomaterials in 3D transparent materials. (c) 2007 Elsevier B.V. All rights reserved.

We report transparent Ni 2+ -doped ZnO–Al 2 O 3 –SiO 2 system glass-ceramics with broadband infrared luminescence. After heat-treatment, ZnAl 2 O 4 crystallite was precipitated in the glasses, and its average size increased with increasing heat-treatment temperature. No infrared emission was detected in the as-prepared glass samples, while broadband infrared luminescence centered at 1310 nm with full width at half maximum (FWHM) of about 300 nm was observed from the glass-ceramics. The peak position of the infrared luminescence showed a blue-shift with increasing heat-treatment temperature, but a red-shift with an increase in NiO concentration. The mechanisms of the observed phenomena were discussed. These glass-ceramics are promising as materials for super broadband optical amplifier and tunable laser.

A set of room temperature low threshold current densities of a mid-infrared InP-based quantum cascade lasers (QCLs) have been demonstrated. Threshold current densities as low as 1.7 kA/cm2 for multi-mode Fabry-Perot QCLs at an emission wavelength of 7.6 μm and 0.9 kA/cm2 for single-mode distributed feedback QCLs at an emission wavelength of 7.7 μm have been achieved at 300 K. The results obtained are through the precision control of doping incorporation and concentration, the active region of the structure for suppressing the current leakage, and the low resistance material choice in the wave guide cladding and plasmon for improving heat dissipation.

Ag/PPy (polypyrrole) composite colloids were prepared through the reaction of silver nitrate with pyrrole solution in DNIF either in the dark, or under the irradiation of femtosecond laser (fs) pulse or UV lamp. The UV-vis spectra of the nanocomposite colloid display an intense absorption band around 620 nm, accompanied by a weak one around 470 nm. The colors and optical absorption spectra of as-synthesized colloids can be reversibly tuned between blue and red, corresponding to absorption band of 620 urn and 526 urn, within few seconds by adding base and acid solutions or gases in turn into the composite colloid suspension. In addition, excess of H+ solution enhanced the absorption band around 470 nm and, at the same time, depressed that around 620 nm. The possible mechanism for the formation and optical absorption properties of the Ag/PPy composite colloid was proposed. (C) 2006 Elsevier B.V. All rights reserved.

We report ultrabroad infrared luminescence from Bi-doped aluminogermanate glasses. The infrared luminescence almost covers the whole low loss wavelength region (1200–1650 nm) of silica glass fiber when excited by a diode laser at 980 nm. The full width at half maximum (FWHM) of the luminescence is 510 nm. The luminescence peak can be divided into three Gaussian peaks, and the fluorescence lifetime of the three emissions are 297 μs, 470 μs and 1725 μs, respectively. These fluorescence properties indicate that the glasses are promising material for broadband optical amplifiers.

Broadband infrared luminescence covering the optical telecommunication wavelength region of O, E and S bands was observed from bismuth-doped zinc aluminosilicate glasses and glass-ceramics. The spectroscopic properties of the glasses and glass-ceramics depend on the thermal-treatment history. With the appearance of gahnite (ZnAl2O4) crystalline phase, the fluorescent peak moves to longer wavelength, but the fluorescent intensity decreases. The ∼1300 nm fluorescence with a FWHM larger than 250 nm and a lifetime longer than 600 μs possesses these optical materials with potential applications in laser devices and broadband amplifiers. The broad infrared luminescence from the bismuth-doped zinc aluminosilicate glasses and glass-ceramics might be from BiO or bismuth clusters rather than from Bi5+ and Bi3+.

In this study, we examined the microstructure of crystals generated in borate glass by femtosecond laser irradiation (FSLI). The distribution of the high-temperature and low-temperature phases of barium metaborate crystals produced in the borate glass is analyzed using Raman spectroscopy. We then propose the possible mechanism for the generation of crystals in glass by FSLI.

The characteristics of the cladding band structure of air-core photonic crystal fibers with silica rings in triangular lattice are investigated by using a standard plane wave method. The numerical results show that light can be localized in the air core by the photonic band gaps of the fiber. By increasing the air-filling fraction, the band gap edges of the low frequency photonic band gaps shift to shorter wavelength, whereas the band gap width decreases linearly. In order to make a specified light fall in the low frequency band gaps of the fiber, the interplay of the silica ring spacing and the air-filling fraction is also analyzed. It shows that the silica ring spacing increases monotonously when the air-filling fraction is increased, and the spacing range increases exponentially. This type fiber might have potential in infrared light transmission.

We report on the effect of various alkaline-earth metal oxides on the broadband infrared luminescence covering 1000‐1600 nm wavelength region from bismuth-doped silicate glasses. The full width at half maximum (FWHM) of the infrared luminescence and the fluorescent lifetime is more than 200 nm and 400 µs, respectively. The fluorescent intensity decreases with increasing basicity of host glasses. Besides the broadband infrared luminescence, luminescence centered at 640 nm was also observed, which should be ascribed to Bi 2+ rather than to the familiar Bi 3+ . We suggest that the infrared luminescence should be assigned to the X2 2 3/2 ! X1 2 1/2 transition of BiO molecules dispersed in the host

Au nanoparticles, which were photoreduced by a Nd:YAG laser in HAuCl4 solution containing TiO2 colloid and accompanied by the TiO2 particles, were deposited on the substrate surface. The film consisting of Au/TiO2 particles was characterized by the absorption spectra, scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. The adhesion between the film and substrate was evaluated by using adhesive tape test. It was found that the presence of TiO2 dramatically enhanced the adhesion strength between the film and the substrate, as well as the deposition rate of film. The mechanism for the deposition of Au/TiO2 film was also discussed. (c) 2005 Elsevier B.V. All rights reserved.

The ternary wide bandgap AlInP alloys have been grown on GaAs substrates by using gas source molecular beam epitaxy, and the relationship between various growth parameters and the composition, lattice mismatch, surface morphology as well as doping concentration of the AlInP epi-layers have been investigated in detail. The AlInP epi-layer with lattice mismatch of +4.3 × 10−4 and full-width at half-maximum of X-ray diffraction peaks of 21.6″ and 14.9″ for epi-layer and substrate respectively have been obtained. The maximum reachable p and n type carrier concentration for Be or Si doping were found to be around 1 × 1018 and 5 × 1018 cm−3 respectively around lattice match composition.

We investigated the effect of cerium oxide on the precipitation of Ag nanoparticles in silicate glass via a femtosecond laser irradiation and successive annealing. Absorption spectra show that Ce3+ ions may absorb part of the laser energy via multiphoton absorption and release free electrons, resulting in an increase of the concentration of Ag atoms and a decrease of the concentration of hole-trapped color centers, which influence precipitation of the Ag nanoparticles. In addition, we found that the formed Ag-0 may reduce Ce4+ ions to Ce3+ ions during the annealing process, which inhibits the growth of the Ag nanoparticles.

We report on space-selective co-precipitation of silver and gold nanoparticles in Ag+, Au3+ co-doped silicate glasses by irradiation of femtosecond laser pulses and subsequent annealing at high temperatures. The color of the irradiated area in the glass sample changed from yellow to red with the increase of the annealing temperature. The effects of average laser power and annealing temperature on precipitation of the nanoparticles were investigated. A reasonable mechanism was proposed to explain the observed phenomena. (c) 2006 Elsevier Ltd. All rights reserved.

Microstructure optical fibers with flat-top fundamental mode are first proposed by introducing a low-index inner core into the core of index-guiding microstructure optical fibers. The design guidelines and characteristics of beam-shaping microstructure optical fibers are demonstrated. The interrelationships of inner-core index with laser wavelength, air hole diameter and size of inner core are investigated. The influence of the relative size of inner core on the spatial profile of the fundamental mode is demonstrated. Moreover, sensitivity of the flat-top fundamental mode profile from the slight change of the optimum inner-core index value is studied. Starting from these results we deduce that it is possible to fabricate beam-shaping microstructure fibers with nowadays technique.

We obtain Au and Ag nanoparticles precipitated in glasses by irradiation of focused femtosecond pulses, and investigate the nonlinear absorptions of the glasses by using Z-scan technique with ns pulses at 532 nm. We observe the saturable absorption behavior for An nanoparticles precipitated glasses and the reverse saturable ones for Ag ones. We also obtain, by fitting to the experimental results in the light of the local field effect near and away from the surface plasmon resonance, chi(m)((3)) = 4.5 x 10(-7) and 5.9 x 10(-8) esu for m the imaginary parts of the third-order susceptibilities for Au and Ag nanoparticles, respectively. The nonlinear response of Au nanoparticles in the glass samples arises mainly from the hot-electron contribution and the saturation of the interband transitions near the surface plasmon resonance, whereas that of Ag nanoparticles in the glass samples from the interband transitions. These show that the obtained glasses can be used as optoelectronic devices suiting for different demands. (c) 2005 Elsevier B.V. All rights reserved.

Au colloids were prepared by irradiation with a Nd:YAG laser. Au nanoparticles were characterized by absorption spectra, transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis. It is found that the wavelength of the laser has no effect on the size but the number of the Au nanoparticles. By irradiating a transparent silica gel doped with gold ions with the focused laser in the gel and subsequent exposing in air, a space-selective pattern of letter “P” consisting of Au nanoparticles was observed inside the silica gel.

The structure of the titanate glass is destroyed during irradiation by the femtosecond laser pulses, and (TiO6)(8-) and (TiO4)(4-) anion units are exsolved from the network of the titanate glass. These anion units are rearranged to form some crystals such as anatase and Ba2TiO4 crystals. By Raman spectroscopy, it is found that these crystals have a strong dependence on the intensity of the femtosecond laser pulses. The relation between the generation of these crystals and space distribution of the femtosecond laser power intensity is qualitatively explained. (c) 2005 Elsevier B.V. All rights reserved.

We report on the optical property changes for Ce 3+ -doped Gd 2 SiO 5 crystal irradiated by a femtosecond (fs) laser. Absorption spectra showed that Ce-related color centers were formed in this crystal after an 800 nm fs laser irradiation. The annealing temperature-dependence of the refractive index and absorption intensity changes have been investigated. Furthermore, a new way of writing overlapped gratings inside the crystal by use of birefringence of fs laser beam in this crystal was proposed.

The broadband luminescence covering 1.2-1.6 mu m was observed from bismuth and aluminum co-doped germanium oxide glasses pumped by 808 nm laser at room temperature. The spectroscopic properties of GeO2:Bi,Al glasses strongly depend on the glass compositions and the pumping sources. To a certain extent, the Al3+ ions play as dispersing reagent for the infrared-emission centers in the GeO2:Bi,Al glasses. The broad infrared luminescence with a full width at half maximum larger than 200 nm and a lifetime longer than 200 mu s possesses these glasses with the potential applications in broadly tunable laser sources and ultra-broadband fiber amplifiers in optical communication field. (c) 2005 Elsevier B.V. All rights reserved.

The heat management of the AlGaAsSb/InGaAsSb ridge waveguide MQW laser at 2 μm wavelength range has been investigated by using the finite-element method (FEM). Results show that the thermal behavior of antimonide lasers is quite different from InP or GaAs-based lasers mainly due to the low thermal conductivities of antimonides, which are coincident with the observed results. By using junction down-mounting or using thick gold plating layer as heat spreader on the top contact for substrate down-mounting, the thermal characteristics of the antimonide lasers can be dramatically improved.

The thermal characteristics of antimonide ridge waveguide MQW lasers have been investigated numerically and experimentally, and compared with phosphide lasers in detail. Using the finite-element method, the heat accumulation and dissipation process of the lasers under CW and pulse driving conditions have been simulated, and quantitative thermal time constants were introduced to describe the cooling efficiency of the lasers. The non-uniform temperature distribution inside the active core of the laser and its effects on lasing spectra have been discussed, and confirmed by the measurement of the broadening of the lasing spectrum towards the blue side. A way to improve the thermal property of antimonide lasers have also been proposed and discussed.

We report refractive index change in a femtosecond laser irradiated Nd3+-doped phosphate glass. The effects of annealing temperature on the refractive index change of the glass have been investigated. Absorption spectra of the glass sample before and after femtosecond laser irradiation and subsequent annealing were measured. The results indicate that multiphoton absorption can undertake although there are intrinsic absorption for the glass in irradiation wavelength. The results may be useful for fabrication of three-dimensional integrated optics devices and waveguide laser devices in this glass. (c) 2004 Elsevier B.V. All rights reserved.

Broadband infrared luminescence covering the optical telecommunication wavelength region of 0, E and S bands was observed in GeO2: Bi, M (M = Ga, B) glasses prepared by conventional melting-quenching technique. The luminescence with a maximum at around 1320 nm possesses a full width at half maximum larger than 300 nm and mean fluorescent lifetime longer than 500 mus when excited by an 808 nm-laser. These glasses may have potential applications in widely tunable laser and super-broadband optical amplifier for the optical communications. (C) 2005 Elsevier B.V. All rights reserved.