Spectroscopic studies of Er3+-Yb3+ codoped multicomposition tellurite oxide glass

Multicomposition of Er3+-Yb3+ codoped tellurite oxide, TeO2-ZnO-PbO-TiO2-Na2O glass has been investigated. A detailed spectroscopic study of the Judd-Ofelt analysis has been performed from the measured absorption spectrum in order to obtain the intensity parameters Ωt (t=2, 4, 6). The calculated Ωt values were then utilized in the determination of transition probabilities, radiative lifetimes and branching ratios of the Er3+ transitions between the J(upper)-J’(lower) manifolds. Both visible upconversion and near-infrared spectra were characterized under the 980 nm laser diode excitation at room temperature

Determination of optimal pumping configuration for an L-band EDFA with 980-nm LD and ASE pumps

L-band gain improvement through amplified spontaneous emission (ASE) pumping was conducted. For an L-band amplifier system employing ASE to improve gain, pumping the system counter-directionally with ASE and codirectionally with 980 mn would yield the best overall performance in terms of gain. Gain improvement as high as 6 dB was attained. (C) 2003 Wiley Periodicals, Inc

Improving the characteristics of the modulation response for fiber Bragg grating Fabry-Perot lasers by optimizing model parameters

A unified and comprehensive study on the small-signal intensity and frequency modulation characteristics of a fiber Bragg grating Fabry-Perot (FBG-FP) laser are numerically investigated. The effect of injection current, temperature, external optical feedback (OFB), nonlinear gain compression factor, fiber grating (FG) parameters and spontaneous emission factor on modulation response characteristics are presented. The rate equations of the laser model are presented in the form that the effect of temperature (T) and external optical feedback (OFB) are included. The temperature dependence (TD) of laser response is calculated according to the TD of laser cavity parameters instead of directly using the well-known Parkove equation. It is shown that the optimum external fiber length (L-ext) is 3.1 cm and the optimum range of working temperature for FGFP laser is within +/- 2 degrees C from the FBG reference temperature (T-o). Also, the antireflection (AR) coating reflectivity and the linewidth enhancement factor have no significant effect on the modulation spectra. It is also show that modulation response is extremely sensitive to the OFB level, high injection current and gain compression factor. The study indicates clearly that good dynamic characteristic can be obtained by system parameters optimization

Experimental realization and performance evaluation of refractive index SPR sensor based on unmasked short tapered multimode-fiber operating in aqueous environments

In this work, we fabricate and characterize an SPR sensor based on unmasked short tapered multimode fiber. The entire taper region is coated with gold without masking offering a simpler approach towards the sensor fabrication. The sensor was tested by immersion in sensing solutions of different refractive indices and the transmittance is measured using a spectrometer system. The sensor performance in terms of sensitivity, detection accuracy, and robustness can be controlled by adjusting the taper physical parameters such as waist diameter, waist length, and transition length. We realize a compact, sensitive, cost-effective and robust SPR sensor suitable for aqueous media sensing by reducing the waist diameter up to 25-45 mu m with a total taper length of 3-5 mm coated with a thin gold film of around 55 nm. The demonstrated sensor exhibits a sensitivity of 1600-2000 nm/RIU and a full width at half maximum (FWHM) of 140-220 nm. (C) 2015 Elsevier B.V. All rights reserved

Australian, Malaysian and Indonesian Accounting Academics' Teaching Experiences During the COVID-19 Pandemic

This study analyses and presents accounting academics' experiences in six universities in Australia, Malaysia, and Indonesia to adapt to the swift change to the remote virtual classroom delivery model forced by the COVID-19 pandemic, while also gaining valuable lessons from this unique situation. In this study, autoethnography's basic principles were used. The main results suggest that the universities' combined current information and communication technologies, learning management systems, blended learning experiences, training, and supports, although not without hitches, were able to accommodate the shift to a remote virtual classroom model quite effectively. However, the move to fully online assessment has been conceded to likely increase the embedded risk of student cheating. The availability of reliable internet connection for students is also crucial in ensuring access equality and effective remote virtual classroom delivery