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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.

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

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.

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.

Nanoparticles have a wide range of electrical and optical properties owing to the quantum-size effect, surface effect, and conjoint effect of nanostructures.[1] Materials doped with noble-metal nanoparticles exhibit large third-order nonlinear susceptibility and ultrafast nonlinear responses.[2] They are expected to be promising materials for ultrafast all-optical switches in the THz region. For the applications related to integrated optoelectronics, a well-defined assembly and spatial distribution of nanoparticles in materials are essential.[3] Many studies have been carried out on the fabrication of nanoparticle-doped materials,[4] but there are no effective methods to control the spatial distribution of nanoparticles in these materials. In addition, Zheng and Dickson reported the synthesis of photostable, water-soluble, silver nanodots by direct photoreduction of silver ions under ambient conditions.[5] Photoactivated fluorescence has also been observed from individual silver nanoclusters.[6] Herein, we report a method that can control the precipitation of Au nanoparticles in three dimensions inside transparent materials by using focused femtosecond laser irradiation. In brief, the precipitation involves two processes: the photoreduction of Au ions to atoms induced by multiphoton process, and the precipitation of Au particles driven by heat treatment. The size of nanoparticles and their spatial distribution can be controlled by the conditions of the lasermore » irradiation. Interestingly, the precipitated nanoparticles obtained by this technique can be also space-selectively “dissolved” by the femtosecond laser irradiation, and reprecipitated by annealing. This implies that the laser can be used not only in practical applications, such as the 3D optical memory and the fabrication of integrated alloptical switches, but also in the study of the control of nucleation and crystal growth.« less

Single crystals of K 2 Ln (NO 3 ) 5 ·2H 2 O ( Ln =La, Ce, Pr, Nd, Sm) (K Ln N) were grown by evaporation in aqueous solution under constant temperature conditions. The structure of KPrN was determined from the single-crystal X-ray diffraction data. The KPrN crystallizes in the orthorhombic space group Fdd 2 with parameters a =21.411(3) A, b =11.2210(10) A, c =12.208(2) A, Z =6, V =2933.0(7) A 3 , R =0.0240, R w =0.0603. The powder second harmonic generation (SHG) intensities of KLn N ( Ln =La, Ce, Pr, Nd, Sm) are also studied. The results demonstrate that their SHG intensities are 4–9 times larger than that of KDP, in which the KPrN shows the highest SHG coefficient.

The sol-gel process has been applied to the preparation of nano-size Sb2S3 crystallite doped silica glasses and thin films. Silica glasses containing 1–1.5 wt% Sb2S3 are prepared by hydrolysis of complex solution of Si(OC2H5)4, SbCl3 and SC(NH2)2, and subsequent heat treatment. The nano-size crystallite in the matrix is observed by means of TEM. The transmission spectra of the films show that the transmission valley shifts toward longer wavelengths with increasing heat treatment time and temperature. Second harmonic generation (SHG) has been observed in the glasses illuminated with intense 1.06 μm and frequency-doubled laser beams from mode-locked Nd:YAG laser.

The hydrolyzation behavior of the Si(OEt)x(OBut)4-x synthesized in part I was investigated by gas chromatogram/mass spectrum (GC/MS) technique. In the Si(OEt)x(OBut)4-x, Si(OEt)(OBut)3 showed more rapid hydrolysis than Si(OEt)2(OBut)2, especially in the initial stages of the hydrolyzation. The dimer and trimer formations along with the sol-gel course were followed during the hydrolyzation process.

Preparation and photochromic behavior of ormosil containing encapsulated AgTCNQ molecules were studied in this paper. The ormosil resulted from hydrolysis and polycondensation of glycidoxypropyltrimethoxysilane, dimethyldimethoxysilane and methyltrimethoxysilane. The time to add AgNO3 water solution into the resultant sol was a key factor to synthesize AgTCNQ molecules inside ormosil matrix. AgTCNQ molecules encapsulated in the ormosil showed different photochromic behavior compared with pure AgTCNQ film: normal photochromic reaction can be realized, while reverse photochromic reaction can not. The “cage” model was used to explain this phenomenon.

Using silicon tetrachloride (SiCl4), tert-butanol (t-BuOH), ethanol (EtOH) and NH3, the hybridized silicon ethoxide 3-tert-butoxide (Si(OEt)x(OBut)4-x) was synthesized and the configuration of the material was investigated by FT-IR,1 H and 13C NMR and gas chromatogram/mass spectrum (GC/MS) techniques. The results confirm that both the ethoxy and the tert-butoxy groups have been attached to silicon atoms. Furthermore, the alkoxy group types and their relative amounts in the alkoxide were also determined by 1H and 13C NMR and GC/MS.

We report on the precipitation control of Au nanoparticles in periodic arrays in silicate glass. Au2O-doped glass samples were first irradiated by two 800 nm interfered femtosecond laser pulses at room temperature and then heat treated at 550 °C for the Au nanoparticle precipitation in the laser irradiation areas. One-dimensional periodic arrays of the Au nanoparticles were controlled by changing the pulse energy and the incident angle between the interfered laser pulses. The smallest dimension in the obtained arrays was a width of 300 nm. The mechanism of the metal nanoparticle precipitation by this technique was discussed. Only two pulses are required to encode these periodic microstructures, which are applicable to emerging nanostructure devices such as optical memory with ultrahigh storage density, micrograting with high diffractive efficiency and integrative micro-optical switches.

We report the precipitation and control of metal nanoparticles inside transparent glasses. An Ag+-doped silicate glass sample was first irradiated by using an 800 nm femtosecond laser at room temperature and then annealed at 550 °C. The area near the focal point of the laser beam became gray after laser irradiation and yellow after further annealing at 550 °C for 10 min. Absorption and electron spin resonance spectra of the glass sample showed that a portion of silver ions near the focused part of the laser beam inside the glass were reduced to silver atoms after the laser irradiation. These silver atoms aggregated to form nanoparticles after further annealing at temperatures above 500 °C. A mechanism is suggested that consists of multiphoton reduction, which is induced by the fundamental light of the laser beam and supercontinuum white light, and diffusion of silver atoms driven by heat energy to form nanoparticles. The observed phenomenon may have promising applications for the fabrication of three-dime...

We report the observation of space-selective oxidation of Mn2+ to Mn3+ in a transparent and colorless Mn and Fe ions codoped silicate glass at room temperature by using an 800-nm-femtosecond laser. Difference absorption spectrum of the glass after and before the irradiation of the focused infrared femtosecond pulsed laser showed that a portion of Mn2+ ions near the focused part of the laser beam inside the glass were oxidized to Mn3+ ions after the laser irradiation. Mn3+ ions were stable at the temperatures below 300 °C. It is suggested that Mn2+ ions act as hole trapping centers while Fe3+ ions as well as active sites in the glass matrix act as electron trapping centers. A promising application was demonstrated for the fabrication of three-dimensional colored image inside a transparent material.

We report near infrared broadband emission of bismuth-doped barium-aluminum-borate glasses. The broadband emission covers 1.3 mum window in optical telecommunication systems. And it possesses wide full width at half maximum (FWHM) of similar to 200nm and long lifetime as long as 350 mus. The luminescent properties are quite sensitive to glass compositions and excitation wavelengths. Based on energy matching conditions, we suggest that the infrared emission may be ascribed to P-3(1) --> P-3(0) transition of Bi+. The broad infrared emission characteristics of this material indicate that it might be a promising candidate for broadband optical fiber amplifiers and tunable lasers. (C) 2005 Optical Society of America.

We report the fabrication of internal diffraction gratings in calcium fluoride crystals by a focused near-IR 800 nm femtosecond laser. The diffraction efficiency and refractive index change were evaluated after femtosecond laser irradiation and subsequent annealing. The maximum refractive index change was estimated to be 3.57x10(-4). Optical absorption spectra, measured for the crystals before and after the laser irradiation and subsequent annealing, indicate that the absorbance increase after femtosecond laser irradiation and decrease with increasing annealing temperature. The mechanisms of refractive index change are proposed. The results may be useful for fabrication of three-dimensional integrated optics devices in the crystals.

The near-infrared emission intensity of Ni(2+) in Yb(3+)/Ni(2+) codoped transparent MgO-Al(2)O(3)-Ga(2)O(3)-SiO(2)-TiO(2) glass ceramics could be enhanced up to 4.4 times via energy transfer from Yb(3+) to Ni(2+) in nanocrystals. The best Yb(2)O(3) concentration was about 1.00 mol%. For the Yb(3+)/Ni(2+) codoped glass ceramic with 1.00 mol% Yb(2)O(3), a broadband near-infrared emission centered at 1265 nm with full width at half maximum of about 300 nm and lifetime of about 220 mus was observed. The energy transfer mechanism was also discussed.

The emission intensity of Ni(2+) at 1200 nm in transparent ZnO-Al(2)O(3)-SiO2 glass ceramics containing ZnAl(2)O(4) nanocrystals is improved approximately 8 times by Cr(3+) codoping with 532 nm excitation. This enhanced emission could be attributed to an efficient energy transfer from Cr(3+) to Ni(2+), which is confirmed by time-resolved emission spectra. The energy transfer efficiency is estimated to be 57% and the energy transfer mechanism is also discussed.

Porous glass with high-SiO2 content was impregnated with Nd ions, and subsequently sintered at 1100 degrees C into a compact non-porous glass in air or reducing atmosphere. Sintering in a reducing atmosphere produced an intense violet-blue fluorescence at 394 nm. However, the sintering atmospheres almost did not affect the fluorescence properties in the infrared range. A good performance Nd3+-doped silica microchip laser operating at 1064 nm was demonstrated. The Nd-doped sintering glasses with high-SiO2 content are potential host materials for high power solid-state lasers and new transparent fluorescence materials. (c) 2007 Elsevier B.V. All rights reserved.

We report a new method for fabricating rare-earth-doped silica glasses for laser materials obtained by sintering nanoporous silica glasses impregnated with rare-earth-doped ions. The fabricated materials have no residual pores and show good optical and mechanical properties. Good performance from a Nd3+-doped silica microchip laser operating at 1.064 mum is successfully demonstrated, suggesting that the fabricated silica glasses have potential for use as active materials for high-power solid-state lasers. (C) 2005 Optical Society of America.

Infrared to ultraviolet and visible upconversion luminescence was demonstrated in trivalent cerium doped YAlO3 crystal (Ce3+: YAP) under focused infrared femtosecond laser irradiation. The fluorescence spectra show that the upconverted luminescence comes from the 5d-4f transitions of trivalent cerium ions. The dependence of luminescence intensity of trivalent cerium on infrared pumping power reveals that the conversion of infrared radiation is dominated by three-photon excitation process. It is suggested that the simultaneous absorption of three infrared photons pumps the Ce3+ ion into upper 5d level, which quickly nonradiatively relax to lowest 5d level. Thereafter, the ions radiatively return to the ground states, leading to the characteristic emission of Ce3+. (c) 2005 Optical Society of America.

We report on an optical interference method for transferring periodic microstructures of metal film from a supporting substrate to a receiving substrate by means of five-beam interference of femtosecond laser pulses. Scanning electron microscopy and optical microscopy revealed microstructures with micrometer-order were transferred to the receiving substrate. In the meanwhile, a negative copy of the transferred structures was induced in the metal film on the supporting substrate. The diffraction characteristics of the transferred structures were also evaluated. The present technique allows one-step realization of functional optoelectronic devices.

Near infrared broadband emission characteristics of bismuth-doped aluminophosphate glass have been investigated. Broad infrared emissions peaking at 1210nm, 1173nm and 1300nm were observed when the glass was pumped by 405nm laser diode (LD), 514nm Ar+ laser and 808nm LD, respectively. The full widths at half maximum (FWHMs) are 235nm, 207nm and 300nm for the emissions at 1210nm, 1173nm and 1300nm, respectively. Based on the energy matching conditions, it is suggested that the infrared emission may be ascribed to 3P1? 3P0 transition of Bi+. The broadband infrared luminescent characteristics of the glasses indicate that they are promising for broadband optical fiber amplifiers and tunable lasers.

Writing computer-generated holograms has been achieved by using near infrared femtosecond laser selective ablation of metal film deposited on glass substrate. The diffraction features with data reconstruction of fabricated computer-generated holograms were evaluated. Both transmission and reflection holograms can be fabricated in a single process. The process required no mask, no pre- or post-treatment of the substrate. (C) 2005 Optical Society of America.

The broadband emission in the 1.2 similar to 1.6 mu m region from Li2O-Al2O3-ZnO-SiO2 ( LAZS) glass codoped with 0.01mol.% Cr2O3 and 1.0mol.% Bi2O3 when pumped by the 808nm laser at room temperature is not initiated from Cr4+ ions, but from bismuth, which is remarkably different from the results reported by Batchelor et al. The broad similar to 1300nm emission from Bi2O3-containing LAZS glasses possesses a FWHM ( Full Width at Half Maximum) more than 250nm and a fluorescent lifetime longer than 500 mu s when excited by the 808nm laser. These glasses might have the potential applications in the broadly tunable lasers and the broadband fiber amplifiers. (c) 2005 Optical Society of America.

We report a controllable process of recipitation and dissolution of silver nanoparticles in ultrashort laser pulses irradiated Ag+-doped phosphate glass. Absorption spectra, transmission electron microscopy and refractive index measurement revealed that metallic silver nanoparticles were precipitated in the glass sample after irradiation by an 800-nm femtosecond laser and subsequent annealing at 300 degrees C, and dissolved after further annealing at 450 degrees C. We discuss a mechanism that combines the formation and decoloration of color centers, precipitation and dissolution of silver nanoparticles.