Spectroscopic Properties of TeO2-Bi2O3-ZnO-PbO Based Tellurite Glasses

Tellurite glasses with molar compositions of 55TeO2–2Bi2O3–[43-x] ZnO–xPbO (in mol%) with x= 1, 2, 3, 4, 5 was fabricated by melt quenching method. Their absorption spectra ranging from ultraviolet to infrared region were measured using UV-VIS-NIR spectrophotometer and FTIR. Minimum losses of all glasses were then estimated from the intersection of the ‘V’ curve formed from the intersection of the extrapolation of the IR edge on the long wavelength side of the spectrum and the scattering loss curve on the short wavelength side of the spectrum. From this work, it was that the estimated minimum loss of the investigated glasses were within the range between 2.31·10-3dB/m and 2.94·10-3 dB/m at wavelength around 5.5 μm.

Photoluminescence Properties of the Magnetoplumbite-Type BaMg6Ti6O19:Mn4+ and Spinel-Type Mg2TiO4:Mn4+

Mn4+-doped magnetoplumbite-type BaMg6Ti6O19 and spinel-type Mg2TiO4 red phosphors were synthesized by a solid-state reaction. BaMg6Ti6O19:Mn4+ and Mg2TiO4:Mn4+ were formed as main phase above 1200 oC. Although the emission peak of BaMg6Ti6O19:Mn4+ and Mg2TiO4:Mn4+ were almost the same, the excitation peak of BaMg6Ti6O19:Mn4+ and Mg2TiO4:Mn4+ were different. The 4A2→4T1 transition peak of Mg2TiO4:Mn4+ shifted to a shorter wavelength side than that of BaMg6Ti6O19:Mn4+ and 4A2→4T2 shifted to a longer wavelength side. The crystal field splitting energy of Mg2TiO4:Mn4+ was lower than that of BaMg6Ti6O19:Mn4+. By the additional of R block, the racah parameter B increased and C decreased. Although the increase of B causes a blue-shift of the emission wavelength and the decrease of C causes a red-shift of the emission wavelength, PL emission wavelength was little different due to the influence of both racah parameter. Thus, it was suggested that the existence of R block results in a difference of photoluminescence properties.

COMPACT WILKINSON PASS-BAND FILTERING POWER DIVIDER BASED ON QUARTER-WAVELENGTH SIDE-COUPLED RING

A Wilkinson power divider with improved bandpass filtering and high isolation performance is proposed. These characteristics are achieved by replacing the quarter-wavelength transmission line in the conventional coupled line Wilkinson power divider with quarter-wavelength side-coupled ring (QSCR). Additional features such as DC blocking between arbitrary two ports, single-layer via-less structure for low-cost fabrication and convenient integration (as only one isolation resistor required) are highlighted. A 2-GHz Wilkinson microstrip power divider with a fractional bandwidth of 4% has been fabricated and experimentally characterized. The consistency between simulated and measured results validates the effectiveness of our proposed design.

Optical Studies on KBr:Tl and KCl-Br:Tl Mixed Crystals

Optical absorption spectra of KBr:Tl+(0.0125 mol%) single crystals shows A, B and C bands around 258, 220 and 210 nm respectively. In KCl0.1Br0.9:Tl+(0.0125 mol%) mixed crystals exhibit slightly broadening of the A-band towards lower wavelength side. The broadening of the absorption spectra are suggested to be due to some complex Tl+centers involving Br-and Cl-ions formed in the mixed crystals. When excited at A, B and C-bands of Tl+ions, PL of KBr:Tl+showed emission band around 320 with a prominent shoulder around 365 nm. In KCl0.1Br0.9mixed crystals the shoulder around 365 nm is not prominent due to the perturbing influence of Cl-ions. Addition bands in the excitation spectra are attributed to the presence of Tl+dimmers. PSL observed in X-ray irradiated crystals resembled their respective PL emissions indicating that PSL in them is due to Tl+ions.