Fu Guang-Sheng

Three-Photon Resonant Nondegenerate Six-Wave Mixing in a Dressed Atomic System

We report a three-photon resonant nondegenerate six-wave mixing (NSWM) in a dressed cascade five-level system. It has advantages that phase match condition is not stringent and NSWM signal is enhanced tremendously due to the multiple resonance with the atomic transition frequencies. In the presence of a strong coupling Held, the three-photon resonant NSWM spectrum exhibits Autler-Townes splitting. This technique provides a spectroscopic tool for measuring not only the resonant frequency and dephasing rate but also the transition dipole moment between two highly excited atomic states.

Luminescence characteristics of Eu 2+ activated Ca 2 SiO 4 Sr 2 SiO 4 and Ba 2 SiO 4 phosphorsfor white LEDs

This paper investigates the luminescence characteristics of Eu2+ activated Ca2SiO4, Sr2SiO4 and Ba2SiO4 phosphors. Two emission bands are assigned to the f–d transitions of Eu2+ ions doped into two different cation sites in host lattices, and show different emission colour variation caused by substituting M2+ cations for smaller cations. This behaviour is discussed in terms of two competing factors of the crystal field strength and covalence. These phosphors with maximum excitation of around 370 nm can be applied as a colour-tunable phosphor for light-emitting diodes (LEDs) based on ultraviolet chip/phosphor technology.

Luminescent properties of Eu3+-doped BaZrO3 phosphor for UV white light emitting diode

Abstract A novel orange phosphor Eu3+ doped barium zirconate (BaZrO3) was synthesized by conventional solid state reaction method and its crystal structure and luminescent properties were investigated in this paper. The X-ray diffraction patterns (XRD) showed that simple BaZrO3 phase was obtained. Monitoring at 596 nm, the excitation spectrum consisted of a broad band and a series of narrow bands and the stronger excitation peaks located at 275 and 393 nm, respectively. The emission spectrum excited by 393 nm UV light was composed of four narrow bands. The strongest emission was located at 596 nm. The appropriate concentration of Eu3+ was 0.025 (molar fraction) for the highest emission intensity at 596 nm. The H3BO3 and ammonium were added as flux and the results showed that 2 wt.% NH4F ions was the optimal flux for BaZrO3:Eu3+.

Synthesis and optical properties of Dy3+, Li+ doped CaMoO4 phosphor

Abstract A series of CaMoO 4 phosphors doped with trivalent dysprosium ions (Dy 3+ ) and lithium (Li + ) were prepared by solid state method at 750 °C for 3 h. X-ray diffraction (XRD) confirmed the crystal structure and quality of phosphors. Scanning electron microscopy (SEM) indicated that the phosphors presented good crystalline state, and the crystalline grain sizes were about 0.5-3.0 μm. The emission spectra showed that the phosphors had intense emission at 480 ( 4 F 9/2 → 6 H 15/2 ), 576 ( 4 F 9/2 → 6 H 13/2 ) and 660 nm ( 4 F 9/2 → 6 H 11/2 ). Meanwhile, the excited spectra indicated it had intense excitation at 352 ( 6 H 15/2 → 6 P 7/2 ), 390 ( 6 H 15/2 → 4 M 21/2 ) and 450 nm ( 6 H 15/2 → 4 I 15/2 ). As a charge compensator, Li + ions were incorporated into CaMoO 4 :Dy 3+ phosphors, which enhanced the PL intensities depending on the doping concentration of Li + . The optimal molar fraction of Dy 3+ ions in Ca 1- x MoO 4 : x Dy 3+ , 0.05Li + was 0.05.

Fabrication and luminescent properties of red phosphor M3BO6:Eu3+(M=La, Y)

Abstract A series of red phosphors M 3 BO 6 :Eu 3+ (M=La, Y) were synthesized at 1150 °C by conventional solid state reaction method and their luminescent properties were investigated. Structural characterization of the luminescent materials was carried out with X-ray powder diffraction (XRD) analysis. Photoluminescence measurements indicated that the La 3 BO 6 :Eu 3+ phosphor exhibited bright red emission centered at about 612 nm 626 nm under UV excited. La 3 BO 6 :Eu 3+ phosphor had better luminescent intensity than Y 3 BO 6 :Eu 3+ phosphors under the same excitation and measuring conditions. It was shown that the 0.08 mol.% Eu 3+ ions in La 3 BO 6 :Eu 3+ phosphors was optimal. The color parameter indicated that La 3 BO 6 :Eu 3+ phosphor was a preferable red phosphor for white LED.

Characteristics of Photoelectron Decay of Silver Halide Microcrystal Illuminated by a Short Pulse Laser

A YAG supershort pulse laser (355nm, 35ps) is used as an exposure source and the microwave dielectric spectrum technique is used to quickly detect the photoelectron decay process in AgX microcrystals, because the free photoelectron lifetime and decay process can decide the sensitivity and other efficiencies of silver halide material. The result shows that the free photoelectron average lifetimes of Kodak-100 and Fuji-100 colour film samples are 8.5 and 9.5 ns, respectively.

Structural and band tail state photoluminescence properties of amorphous SiC films with different amounts of carbon

Amorphous silicon carbide films are deposited by the plasma enhanced chemical vapour deposition technique, and optical emissions from the near-infrared to the visible are obtained. The optical band gap of the films increases from 1.91 eV to 2.92 eV by increasing the carbon content, and the photoluminescence (PL) peak shifts from 1.51 eV to 2.16 eV. The band tail state PL mechanism is confirmed by analysing the optical band gap, PL intensity, the Stocks shift of the PL, and the Urbach energy of the film. The PL decay times of the samples are in the nanosecond scale, and the dependence of the PL lifetime on the emission energy also supports that the optical emission is related to the radiative recombination in the band tail state.

Growth of Nanocrystalline Silicon Films by Helicon Wave Plasma Chemical Vapour Deposition

Nanocrystalline silicon (nc-Si) thin films have been prepared by a helicon-wave plasma chemical vapour deposition technique on glass–Si substrates. The structural properties and the surface morphology are characterized by Raman spectroscopy, x-ray diffraction and atomic force microscopy. It is proven that the deposited films have the features of high crystalline fraction and large grain size compared with that in the normal plasma-enhanced chemical vapour deposition regime. The crystalline fraction of the deposited films varying from 0% to 72% can be obtained by adjusting the substrate temperature.

Effect of Eu3+ contents on structure and luminescence properties of Na3Bi2-x(PO4)3:xEu3+ and Na3Bi1-x(PO4)2:xEu3+ phosphors

Abstract A series of Na 3 Bi 2- x (PO 4 ) 3 : x Eu 3+ and Na 3 Bi 1- x (PO 4 ) 2 : x Eu 3+ phosphors were successfully synthesized by solid-state method. The structure and luminescence properties were carefully investigated. The excitation spectra presented an obvious excitation band, and the peak was located at 396 nm, which matched well with the popular emissions from near-UV light-emitting diode chips. With the phase of Na 3 Bi 2- x (PO 4 ) 3 : x Eu 3+ changing to that of Na 3 Bi 1- x (PO 4 ) 2 : x Eu 3+ , the intensity of magnetic dipole transition ( 5 D 0 →F 1 ) at 598 nm became stronger than that of electric dipole transition ( 5 D 0 → 7 F 2 ) at 621 nm. Under 396 nm excitation, the chromaticity coordinates and the decay curves of the entitled phosphors were also investigated. Based on all experiments without concentration quenching, we could control the luminescence intensity of the material by adjusting the doping amount of the active ions. All results indicated that Na 3 Bi 2- x (PO 4 ) 3 : x Eu 3+ and Na 3 Bi 1- x (PO 4 ) 2 : x Eu 3+ phosphors have potential application as red phosphors in near UV chip-based white light emitting diodes.

Effect of Aluminium Nanoparticles on the Performance of Bulk Heterojunction Organic Solar Cells

Al nanoparticles (NPs) are incorporated in the active layers to enhance the performance of organic solar cells (OSCs). The improved short circuit current Jsc and power conversion efficiency (PCE) for OSCs with Al NPs are observed. A final PCE of 3.66wt% is achieved, which is an improvement of more than 30wt% compared to a standard cell with a PCE of 2.84wt%. When the mass of Al NPs is 10wt% of OSCs, the device performance is best. The optical performance of OSCs reveals that the absorption from sunlight increases. The external quantum efficiency spectra suggests that the Al NPs in the active layers influence the efficiency of converting photons into electrons, which leads to the improvements in the photocurrent. The enhanced photovoltaic performance induced by incorporating Al NPs in the active layer is discussed in the terms of increasing charge separation at the donor-acceptor interface and the effectively decreasing transmission distance of charge in polymer.