Comparison of Sterilizing Effect of Nonequilibrium Atmospheric-Pressure He/O_2 and Ar/O_2 Plasma Jets

The sterilizing effect of the non-equilibrium atmospheric pressure plasma jet by applying it to the Bacillus subtilis spores is invesigated. A stable glow discharge in argon or helium gas fed with active gas （oxygen）, was generated in the coaxial cylindrical reactor powered by the radio-frequency power supply at atmospheric pressure. The experimental results indicated that the efficiency of killing spores by making use of an Ar/O2 plasma jet was much better than with a He/O2 plasma jet. The decimal reduction value of Ar/O2 and He/O2 plasma jets under the same experimental conditions was 4.5 seconds and 125 seconds, respectively. It was found that there exists an optimum oxygen concentration for a certain input power, at which the sterilization efficiency reaches a maximum value. It is believed that the oxygen radicals are generated most efficiently under this optimum condition.

Luminescence Properties of Phosphate Phosphor: Barium Tungstate Doped with Dy

A series of barium-tungstate-based phosphors doped with different concentrations of Dy3+ were synthesized by solid-state reaction method. Photoluminescence properties and decay lifetime of Dy3+-doped BaWO4 samples were studied. The results indicated that luminescent properties of BaWO4:Dy3+ depended on the Dy3+ concentration, and the inner energy could transfer from to Dy3+. The quality of the light was checked by estimating CIE parameters, and the results showed that BaWO4:Dy3+ was a potential candidate as blue-green luminescent materials in white LED because of its excellent emission spectrum excited by UV light.

Optimizing bowtie structure parameters for specific incident light

We investigate optical properties of a bowtie-shaped aperture using the finite difference time domain method to optimize its geometric parameters for specific incident lights. The influence of the parameters on local field enhancement and resonant wavelength in the visible frequency range is numerically analysed. It is found that the major resonance of the spectrum is exponentially depended on the bowtie angle but independent of the whole aperture size. The simulation also demonstrates that increasing the aperture size raises the local field intensity on the exit plane due to an enlarged interaction area between the light and the metal medium. And the near-field spot size is closely related to the gap. Based on these results, the design rules of the bowtie structure can be optimized for specific wavelengths excited.

Luminescence properties of red phosphors Ca_(10)Li(PO_4)_7:Eu^(3+)

A series of red phosphors Ca10Li （PO4）7：Eu3＋ were synthesized by high temperature solid-state reaction method. Their luminescence properties were characterized by means of photoluminescence excitation and emission spectra,CIE chromaticity and quantum efficiency. Results indicated that the phosphors could be effectively excited by the near ultraviolet （NUV） light （393 nm）. The main emission peaks of the phosphor were ascribed to the transition 5D0–7F2 （613 and 617 nm） of Eu3＋ ion when samples were excited by 393 nm. The CIE chromaticity （x,y） of Ca9.9Li （PO4）7：0.10Eu3＋ was x=0.638,y=0.361 and the quantum efficiency of this phosphor was 75% excited by 393 nm. Therefore,this phosphor could be a promising red component for the applications in white LEDs.

Hydrothermal synthesis and luminescence properties of Eu^(3+) and Sm^(3+) codoped BiPO_4

Eu3＋/Sm3＋codoped BiPO4 phosphors were synthesized via a facile hydrothermal method with surfactant-free environment. The X-ray diffraction analysis demonstrated that the samples possessed the standard BiPO4 monoclinic structure. Scanning electron microscopy images showed that all samples composed of well-dispersed, micrometer-sized crystals with shuttle-like shape. Energy transfer from Sm3＋to Eu3＋was confirmed by the luminescence spectra and the decay processes of Sm3＋ 4G5/2→6H5/2 emission. Or-ange-red luminescence could be obtained in Eu3＋/Sm3＋codoped BiPO4 phosphors. The average lifetime of Sm3＋ 4G5/2→6H5/2 emis-sion decreased from 2.70 ms in BiPO4：0.03Sm3＋ to 2.37 ms in BiPO4：0.03Sm3＋,0.05Eu3＋. The strong and wide absorption band around 395 nm, originating from both 7F0→5L6 transition of Eu3＋and 6H5/2→4K11/2 transition of Sm3＋, endowed BiPO4：Eu3＋,Sm3＋phosphors with the potential application in the fields of near UV-excited white-light-emitting diodes.

Study on the characteristics of erbium-doped waveguide ring laser

A theoretical model of the erbium-doped waveguide ring laser is established according to the theory of erbium-doped waveguide amplifier and the transmission matrix of waveguide directional coupler. The influence of bend radius, coupling coefficient and doped erbium ion concentration on the characteristics of waveguide ring laser is investigated. It is shown that due to the co-action of waveguide bend loss and other relevant loss there is an optimal bend radius which can provide simultaneously low threshold pumping power and high laser light output power. As one part of the resonator’s loss, the laser light coupling coefficient of directional coupler has an impact on the laser property. The analysis indicates that the laser achieves the high output power when the coupling coefficient is about 0.2. The threshold pumping power is the minimum when the doped erbium ion concentration is 0.85×1026 m−3. Increasing the concentration of doped erbium ions will enhance the output power of laser light as long as the concentration doesn’t introduce remarkable up-conversion effect. The results give a good theoretical basis for the design and fabrication of erbium-doped waveguide ring laser devices.

Rate equation model analysis on the infrared and upconversion emission of Er/Yb co-doped borate-silicate glass

Er/Yb co-doped borate-silicate glasses with various Yb concentrations were fabricated by high-temperature solid-reaction method.The photoluminescence spectra around 1.55 μm and the visible upconversion spectra were measured.The radiative lifetime of Er-4I13/2,com-pared with the measured one,was obtained by Judd-Ofelt theory based on the absorption spectra.A rate equation model for Er/Yb co-doped system has been established based on the data obtained from the measurements,including the absorption and emissio...

Novel method for fiber chromatic dispersion measurement based on microwave photonic technique

In this letter, we propose and demonstrate a simple and novel method for fiber chromatic dispersion （CD） measurement based on microwave photonic technique. The radio frequency （RF） signal is modulated simultaneously on two light-waves with different wavelengths, and the light-wave carrying RF signals transmit through the dispersive medium under test. CD can be obtained by monitoring the power changing of the interference RF signals after photo detector. The CD values of the single-mode and dispersion compensation fibers are both measured within the wavelength range from 1 525 to 1 605 nm, which verifies the feasibility of this method.