J.A. Medeiros Neto

Quantum-efficiency of praseodymium doped Ga:La:S glass for 1.3 /spl mu/m optical fibre amplifiers

The gain of Pr/sup 3+/-doped ZBLAN fibre amplifiers is hindered by a poor quantum efficiency due mainly to a high rate of multiphonon decay. Sulphide-based glasses ameliorate this problem through a higher radiative rate and lower nonradiative rate. In this letter, Pr/sup 3+/-doped Ga:La:S glass has been evaluated spectroscopically in bulk and fibre form for its quantum-efficiency at 1.3 microns. Measurements reveal that absorption bands are broadened and the effective separation between the /sup 1/G/sub 4/ and /sup 3/F/sub 4/ level is reduced compared to ZBLAN glass. Judd-Ofelt analysis and the theory of multiphonon-decay now predict efficiencies of 80%, while 58% is measured. Oxide impurities are shown to play a key role in quenching of the radiative emission.<<ETX>>

Application of a modified Judd-Ofelt theory to praseodymium-doped fluoride glasses

Using the original Judd-Ofelt theory and a more recent modified Judd-Ofelt theory, the radiative properties of praseodymium in a series of halide glasses are predicted. Experimental and measured oscillator strengths are presented and Judd-Ofelt parameters are determined by both methods for all glasses. The calculated radiative lifetimes are compared with the experimentally measured values for the 1D2 energy level and the suitability of the two models are compared. Results show that the modified theory provides better agreement with the experimentally measured lifetimes for the 1D2 transition

The application of Ga:La:S-based glass for optical amplification at 1.3 μm

Abstract The optical properties of praseodymium-doped low-phonon-energy glasses have recently attracted considerable attention for their potential application as a 1.3 μm Pr +3 -doped optical fibre amplifier. Sulphide glasses based on Ga 2 S 3 and La 2 S 3 are amongst the lowest-phonon-energy glasses which are suitable for this application, with quantum efficiencies exceeding 50% currently measured on bulk samples in the laboratory. The purpose of this paper is to describe the thermal, optical and spectroscopic properties of Pr +3 -doped sulphide-based glasses, present the results of amplifier modelling using the measured cross-sections, and report the progress to date in achievement of a Pr +3 -doped sulphide-based fibre.

Spectroscopy of Pr3+-doped low-phonon-energy glasses based on halides and sulfides

The optical properties of praseodymium-doped glasses have attracted considerable attention recently for their potential application as a 1.3 micron optical amplifier. We report here on our spectroscopic evaluation of a series of low-phonon-energy glasses based on halides and sulphides. These results, though driven by the desire for a practical amplifier, provide insight into the application of these glasses not only for telecommunications applications, but also an understanding of the overall optical properties of a low-phonon-energy glass. Using Raman spectroscopy, the vibrational characteristics of the glass host are determined. Absorption measurements across the visible and infrared allow evaluation of the intrinsic loss of these glasses when in fiber form, as well as providing an indication of glass purity. Fluorescence of Pr3+-doped glasses, through excitation of the 3P0, 1D2 and 1G4 levels, is measured along with the fluorescence lifetimes. These radiative properties are compared to those predicted by a Judd-Ofelt analysis, which has been performed on all glasses. In this way, this work provides an overall spectroscopic evaluation of the optical properties of low-phonon-energy glasses, leading the way towards a practical device.

Reversible non-linear electrical switching in CdTeS-doped glass

The electrical switching behaviour of CdTexS1−x-doped borosilicate glass was studied by determining the d.c. current-voltage characteristics using a current source. The I-V characteristic is non-linear for high current density, leading to deviation from Ohms law. The experimental data have been analysed assuming that the increase in the glass conductivity is dominated by the Joule effect. The theoretical model used is in good agreement with the experimental results.

Application of low-phonon energy glasses for optical amplification at 1.3 μm

We report on recent progress towards the application of both mixed cadmium halides and sulphide-based glasses as host materials for a Pr3+-doped 1.3 micron optical fiber amplifier. Both of these materials offer the potential for higher gains than can be currently achieved in a Pr3+-doped ZBLAN fiber. Fundamental glass properties, including optical and thermal characteristics, are compared. Losses of these glasses in fiber form have been estimated and spectroscopic measurements are summarized. From these studies we show that quantum efficiencies over an order of magnitude higher than those demonstrated with Pr3+-doped ZBLAN amplifiers are in principle obtainable. Measured efficiencies of 11% and 52% for the Cd halide and Ga sulphide, respectively, are achieved, while 25% and 80% are predicted. Numerical modelling allows comparison of the expected amplifier performance. Thermal analysis has identified the challenges which remain for the drawing of single mode fibers and the results of preliminary fiber drawing trials are described. The relative merits of each of the various glasses are considered and the challenges before a practical amplifier is achieved are outlined.

NONLINEAR ELECTRICAL SWITCHING IN CDTES DOPED GLASS

The electrical switching behaviour of CdTexS1-x doped borosilicate glass was studied by determining the D.C. current-voltage characteristics using a current source. The I-V characteristic is non-linear for high current density leading to deviation from Ohms law. The experiment data have been analysed under the assumption that the increase of the glass conductivity is dominated by the Joule effect. The used theoretical model is in good agreement with the experimental results.