Search

Four types of shape and crystal structure-controlled WO 3 (normal: N-WO 3 , disk: D-WO 3 , cuboid: C-WO 3 , hexagonal plate: H-WO 3 ) were synthesized from starting reagent of (NH 4 ) 10 W 12 O 41 ·5H 2 O by pyrolysis (N-WO 3 ), precipitation (D-WO 3 ) and hydrothermal (C-WO 3 and H-WO 3 ) methods. N-WO 3 and D-WO 3 have monoclinic and triclinic mixed phases each. C-WO 3 has monoclinic phase, and H-WO 3 has hexagonal phase mixed with monoclinic phase. Pt particles-loaded WO 3 (Pt/WO 3 ) was prepared to improve photocatalytic activity. Among four types of Pt/WO 3 , Pt/C-WO 3 shows the highest photocatalytic activity for the degradation of methylene blue (MB) under visible-light irradiation, and photocatalytic activity decreases in the order Pt/C-WO 3 ≈ Pt/H-WO 3 > Pt/D-WO 3 ≫ Pt/N-WO 3 . The MB degradation ability per unit specific surface area after visible-light irradiation for 6 h decreases in the order Pt/H-WO 3 ≫ Pt/C-WO 3 > Pt/D-WO 3 > Pt/N-WO 3 , suggesting that with similar specific surface area of WO 3 , the hexagonal phase is more favorable for MB degradation than the monoclinic phase. This is believed to be due to the high MB adsorption ability of the hexagonal phase. Scavengers for OH radicals, holes and excited electrons were added to MB aqueous solution to investigate the degradation mechanism of MB on each Pt/WO 3 . In the case of Pt/C-WO 3 and Pt/H-WO 3 , OH radicals and holes were the main oxidants in the degradation process of MB, where OH radical ( OH) generation could be attributed to oxidation of H 2 O by holes.

We discuss the synthesis of cuboid-monoclinic tungsten oxide (C-m-WO3) particles and hexagonal-plate-like-hexagonal tungsten oxide (H-h-WO3) particles by acidification and hydrothermal treatment with (NH4)10W12O41·5H2O as a starting material. From the WO3 particles, thin- and thick-film gas sensors were fabricated for NO2 sensing applications and the effect of the morphology and crystal structure of the WO3 particles on the NO2 sensing properties was investigated. The extremely high sensor responses of 160 to 20 ppb NO2 and 10 120 to 500 ppb NO2 were obtained for a C-m-WO3 thin-film sensor at an operating temperature of 200 °C. The crystal structure features of as-prepared particles were studied by XRD, XPS, SEM, TEM, and solid state 1H and 13C NMR measurements. The presence of residual impurities, cations, and high density of surface OH− in the H-h-WO3 particles was demonstrated, which could be one of the key reasons for the crystal structure dependence of the sensing properties in C-m-WO3 and H-h-WO3 gas sensors.

The fluorescence characteristics of different Ce3+:Er3+-codoped fluoride host glasses, such as fluorozirconate and fluoroindate glass, are reported. It is shown that Ce3+ codoping into Er3+ doped fluoride glasses resulted in a quenching of Er3+ ions from the 4I11/2 to the 4I13/2 state, and the branching ratio for the Er3+ 4I11/2→4I13/2 transition increased from 0.20 to over 0.80 by codoping 2.0 mol % Ce3+. Further, the fluorescence quantum yield at 1.55 μm was also significantly improved. A Ce3+:Er3+-codoped fluorozirconate fiber laser operating at 1.55 μm band with 980 nm excitation has been realized for the first time, which clearly indicates the effectiveness of Ce3+ codoping.

We demonstrate the low-noise and high-gain operation of a fluoride Er/sup 3+/ and Ce/sup 3+/ codoped fiber (F-ECDF) amplifier with 980-nm pumping. A 980-nm-pumped F-ECDF with a length of only 45 cm exhibits a noise figure of 20 dB with a gain ripple of

We tried to fabricate WO 3 thin-film sensors using four kinds of WO 3 particles with very different crystalline morphologies (spherical, disk, cuboid, and hexagonal). Using highly dispersive suspensions prepared, WO 3 thin films of 1.5–3.0 μm in mean thickness were obtained by micro-injecting film formation method. NO 2 sensing properties of these thin-film sensors suggested that the sensitivity to NO 2 as well as the rate of response-recovery depended markedly on morphology and microstructure of the WO 3 crystals contained.

Fiber laser operating property at 1.55-/spl mu/m band in a newly developed Ce,Er:ZBLAN fiber by a continuous-wave laser diode pumping at 980 nm is presented. The output characteristics of the Ce,Er:ZBLAN fiber laser system are analyzed in detail based on the rate equations model by taking into account the energy transfer between Ce/sup 3+/ and Er/sup 3+/ ions, as well as the upconversion mechanisms. The promotion role of the Ce in the erbium-doped ZBLAN for the 1.55-/spl mu/m band fiber laser operation has been realized.

To improve 1.55 /spl mu/m band fluorescence, Ce and Yb were doped into Er doped ZBLAN glasses, the fluorescence characteristics and energy transfer dynamics of Ce:Er:Yb:ZBLAN glasses were investigated.

Er-doped heavy-metal fluoride glass, because of its wider emission bandwidth around 1500 nm, which spans the most important communications window, now has been investigated as one of the most promising materials for wide-band optical fiber amplifier, which would be of great value in the future wavelength division multiplexing (WDM) optical fiber communication system. However, one drawback of Er-doped fluoride glass is its low branching ratio leading to 1.55 /spl mu/m amplification under 980 nm excitation which is adopted for a low noise amplifier. Now this problem is expected to be solved by the rare earth co-doping technique. It has been proved that Ce co-doping into Er-doped fluoride glasses significantly improved the fluorescence quantum yield for the 1.55 /spl mu/m transition with 980 nm excitation. The Ce,Er co-doped fluoride glass is expected to be a new candidate material of a fiber amplifier for WDM.

Optical glasses doped with a fullerene mixture of C60/C70 were made in our lab. Three peaks, corresponding to C60, C70, and a modified fullerene (possibly its oxide), respectively, were found in the chromatogram of high performance liquid chromatography (HPLC) analysis of the 0.1‐wt % fullerene doped phosphate glass. Depending on the doping procedure and impurity, weak to strong interacting between C60 and its environment was found by the nuclear magnetic resonance study. For both phosphate and fluorophosphate glasses with 0.01‐wt % fullerene mixture doping, the eigen UV absorption edge showed a significant blueshift, indicating that the bonding between the nonbridging oxygen in these glasses was subjected to a strong change due to the fullerene doping.

We present the experimental results on how to suppress self‐mode‐locking in a free‐run or Q‐switched Nd:YAG laser with intracavity fullerenes. It was demonstrated that the self‐mode‐locking was partly or completely suppressed when a certain sample containing fullerenes, such as C60 toluene solution, C60 in polystyrene host, or optical glass doped with fullerenes, was placed within the laser resonator, and that the degree of suppression was dependent upon the length and fullerenes concentration of the sample. Qualitative analysis showed that the nonlinear absorption of the intracavity fullerenes resulted in this effect.

Fiber laser operation at 1.55 /spl mu/m band was first time realized in a Ce/sup 3+/:Er/sup 3+/:ZBLAN multimode fiber by cw LD pumping at 980 nm. The performance of wavelength tunable fluoride fiber laser around 1.55 /spl mu/m has been achieved.

The fluorescence characteristics of Er/sup 3+/ codoped with Ce/sup 3+/ or Yb/sup 3+/ in ZBLAN glass were studied. It was found that the 1.55 /spl mu/m band fluorescence characteristics can be effectively improved by Ce/sup 3+/-codoping, and dynamics of the transfer and back transfer among Yb/sup 3+/ and Er/sup 3+/ ions in fluoride glasses can be well described by the energy transfer model.

Energy transfer dynamics in fluorozirconate glass doubly-doped with Yb3+:Er3+ and Ce3+:Er3+ have been analyzed by using rate equation formalism. For the Yb3+:Er3+-ZBLAN glass, the macroscopic energy transfer parameters, cross-relaxation coefficients, were derived to be 1.1*10-17s-1cm3 and 2.0*10-17s-1cm3 for the forward energy transfer (Yb3+ → Er3+) and the backward transfer (Er3+ → Yb3+), respectively. After experimentally investigating fluorescence characteristics of Er3+ ions in the Ce3+:Er3+-ZBLAN glass, taking into account of up-conversion and energy transfer effect, a resonant cascade energy transfer model was developed, with which the operating mechanism of the Ce3+:Er3+-ZBLAN fiber laser was explained theoretically. The potentiality of the rare-earth-codoped fluoride glass as one of the most promising laser materials is demonstrated.

Four types of WO3 particles, spherical, disk, cuboid, and hexagonal, were prepared and WO3 film sensors were deposited on Au comb-type microelectrodes by dropping suspension using the various WO3 powders obtained. The sensing properties to dilute NO2 revealed that the cuboid WO3 film sensor had the best response-recovery characteristics with the 90% response and 90% recovery times of 1.3 and 0.9 min to 0.05 ppm NO2 at 200°C, respectively. On the other hand, the hexagonal WO3 film sensor showed extremely high sensor response of 41.1 even to 0.01 ppm NO2 at 200°C, but the sensor response fluctuates widely with the operating temperature ranging from 80 to 300 °C. The adsorption-desorption behaviours of NO2 on various surfaces of WO3 particles with different morphologies were investigated using temperature programmed desorption (TPD) technique, which suggesting that NO2 molecules were adsorbed easily on the WO3 surface. The desorbed amount of NO decreased in the order of hexagonal, cuboid, disk and spherical, which agreed with the respective sensor response of the four WO3 film sensors.

Piezoelectric microdevices using lead zirconate titanate (PZT) bulk ceramics are desired for use in actuators requiring a large driving force. We have designed a fabrication process for microdevices using PZT bulk ceramics together with Si single crystals. The key techniques of the process are the bonding of PZT bulk ceramics to Si single crystals, the thinning of bulk ceramics, and the micromachining of bulk ceramics. PZT ceramics were bonded to Si using a gold thin film as an intermediate layer. The tensile strength of the PZT-Si bonded wafers depended on the PZT poling process. A dicer or a KrF excimer laser was used to cut the PZT ceramics along the designed pattern. A PZT-Si diaphragm was fabricated as an example of a basic structure that can be used in a device such as a piezoelectric micropump.

The fluorescence characteristics of Ce3+:Er3+ codoped fluoride glass are reported. It is observed that the decay rate of the 4I11/2 state of Er3+ increased by increasing the Ce3+ concentration. Further, the branching ratio for the transition from the 4I11/2 state to the 4I13/2 state of Er3+ increased from 0.20 to 0.95 by codoping 6.0 mol% Ce3+ into Er3+-doped ZBLAN-H fluoride glass. As a result, the 1.55 µm fluorescence quantum yield has been significantly improved.