Quanzhong Zhao

Near infrared broadband emission of bismuth-doped aluminophosphate glass

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.

Infrared broadband emission of bismuth-doped barium-aluminum-borate glasses.

We report near infrared broadband emission of bismuth-doped barium-aluminum-borate glasses. The broadband emission covers 1.3microm window in optical telecommunication systems. And it possesses wide full width at half maximum (FWHM) of ~200nm and long lifetime as long as 350micros. 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 3P1? 3P0 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.

Direct writing computer-generated holograms on metal film by an infrared femtosecond laser.

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

Controllable precipitation and dissolution of silver nanoparticles in ultrafast laser pulses irradiated Ag+-doped phosphate glass.

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.

Redistribution of elements in glass induced by a high-repetition-rate femtosecond laser.

The redistribution of elements in a multicomponent oxyfluoride glass is induced by a 250 kHz femtosecond laser. Elemental distribution in the cross section of the modified region along the laser propagation axis is analyzed by an electron microprobe analyzer. The results indicate that the relative concentrations of network formers of the glass are higher in the central area of the modified region and lower in the periphery of the modified region compared with the unirradiated areas. However, the relative concentrations of network modifiers are as opposed to that of network formers. Fluorescence spectra confirm that the distribution of fluorescence intensity of Yb(3+) in the modified region is consistent with that of its concentration. The effects of spherical aberration of the incident beam on the elemental redistribution are also discussed.

Radioprotection by fullerenols of Stylonychia mytilus exposed to γ-rays

The aim was to study the protective effects of fullerenols, C60(OH)x, on Stylonychia mytilus cells exposed to 60Co γ-rays and the probable mechanisms of fullerenols protection. Ciliated protozoans Smytilus, kept in solutions of fullerenols at different concentrations, were irradiated with 60Co γ-rays to various dose levels. Surviving cells were counted each day over 5 days after irradiation, and the surviving fraction was calculated. The relations of the surviving fraction to radiation dose and to fullerenols concentration were studied. Superoxide dismutase (SOD), catalase (CAT), malondialdehyde (MDA) and lipofusion (LIP) levels in S. mytilus were also measured. The surviving fraction of S. mytilus decreased with increasing γ-ray doses from 100 to 2000 Gy. Fullerenols enhanced the surviving fraction, except for the highest γ-ray dose level. The maximum protection by fullernols occurred at a concentration of 0.10 mg ml – 1. However, fullerenols at concentration of 0.25 mg ml – 1 yielded a surviving fraction lower than that for the control sample. Fullerenols at a concentration of 0.10 mg ml – 1 increased the SOD and CAT activities in the γ-ray plus fullerenols (γ + F) group compared with the levels in both the γ-ray (γ) group (p < 0.01) and the control group (p < 0.01). The MDA and LIP levels in the γ + F groups (p < 0.01) were significantly lower than that in both the control group (p < 0.05) and the γ group (p < 0.01). At a concentration of 0.25 mg ml – 1, fullerenols reduced the SOD and CAT activities, but increased the MDA and LIP level compared with the control. There was no significant difference in SOD and CAT activities between the γ + F group and γ group. While the MDA and LIP level in the γ + F and γ groups were similar at a dose of 500 Gy, the LIP level in the γ + F group was significantly higher than that in the γ group (p < 0.01) at a dose of 2000 Gy. Fullerenols are good radiation protectors for the protozoan S. mytilus exposed to γ-rays. The effectiveness of radioprotection depends on both fullerenols concentration and γ-ray dose. The protective effect of fullerenols on damage induced by γ-rays seems to be mediated, at least in part, through their anti-oxidative and radical scavenging activities.

Fabrication of internal diffraction gratings in calcium fluoride crystals by a focused femtosecond laser

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.

Optical waveguides in TiO 2 formed by He ion implantation

We report on the formation and the optical properties of the planar and ridge optical waveguides in rutile TiO₂ crystal by He+ ion implantation combined with micro-fabrication technologies. Planar optical waveguides in TiO₂ are fabricated by high-energy (2.8 MeV) He+-ion implantation with a dose of 3 × 10¹⁶ ions/cm² and triple low energies (450, 500, 550) keV He+-ion implantation with all fluences of 2 × 10¹⁶ ions/cm² at room temperature. The guided modes were measured by a modal 2010 prism coupler at wavelength of 1539 nm. There are damage profiles in ion-implanted waveguides by Rutherford backscattering (RBS)/channeling measurements. The refractive-index profile of the 2.8 MeV He+-implanted waveguide was analyzed based on RCM (Reflected Calculation Method). Also ridge waveguides were fabricated by femtosecond laser ablation on 2.8 MeV ion implanted planar waveguide and Ar ion beam etching on the basis of triple keV ion implanted planar waveguide, separately. The loss of the ridge waveguide was estimated. The measured near-field intensity distributions of the planar and ridge modes are all shown.

Pressure-induced crystallization in a bulk amorphous Zr-based alloy

Crystallization of multi-component on amorphous Zr-based alloy (Zr41Ti14Cu12.5Ni9Be22.5Cl) is investigated at different pressures and temperatures. We have previously found that the primary crystallization temperature decreases with increasing pressure below 6 GPa, and the crystallization follows a different process under high pressure when compared to that at ambient pressure. In this work, pressure-induced crystallization is observed by in situ X-ray diffraction (XRD) using synchrotron radiation in a diamond anvil cell at similar to25 GPa and room temperature. This phase transition between amorphous and crystalline is reversible and the crystallized sample returns to the amorphous state during decompression. The mechanism for pressure-induced crystallization is discussed. We suggest that the crystallized phases under high pressure are interstitial solid solution phases formed from the amorphous matrix without long-range atomic rearrangements

Ellipsometric characterization of LaNiO3−x films grown on Si (111) substrates: Effects of oxygen partial pressure

LaNiO3−x films have been grown on Si (111) substrates under different oxygen partial pressures using radio frequency magnetron sputtering. X-ray diffraction shows that these films are polycrystalline with a highly (100)-preferential orientation. The optical properties of the LaNiO3−x films have been systematically investigated by spectroscopic ellipsometry (SE) in the wavelength range of 400–1700 nm. For interpreting the SE experimental data, a parametrized Drude and double Lorentzian oscillator dispersion relation has been used to model the optical response of the LaNiO3−x films. The relations between the optical constants of the LaNiO3−x films and oxygen partial pressure have been characterized in detail. The resistivity can be calculated by the Drude term and these ellipsometric analysis results are nearly consistent with the electrical dc measurements. The resistivity (these values are about 5.5×103 μΩ cm) obtained by spectroscopic ellipsometry shows that these films would be good to use as bottom ele...