B.N. Samson

Spectroscopic data of the 1.8-, 2.9-, and 4.3-μm transitions in dysprosium-doped gallium lanthanum sulfide glass

Infrared emission at 1.8, 2.9, and 4.3 microm is measured in dysprosium-doped gallium lanthanum sulfide (Ga:La:S) glass excited at 815 nm. Emission cross sections were calculated by Judd-Ofelt analysis, the Füchtbauer- Ladenburg equation, and the theory of McCumber. The sigmatau value for the 4.3-microm transition is ~4000 times larger in the Ga:La:S glass than in a dysprosium-doped LiYF(4) crystal, which has lased on this transition. The large sigmatau value and the recently reported ability of Ga:La:S glass to be fabricated into fiber form show the potential for an efficient, low-threshold mid-infrared fiber laser. The f luorescence peak at 4.3 microm coincides with the fundamental absorption of atmospheric carbon dioxide, making the glass a potential laser source for gas-sensing applications.

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>>

Spectral properties of Er3+-doped gallium lanthanum sulphide glass

Abstract The spectral properties of chalcogenide glass 0.7Ga2S3:0.3La2S3 (Ga:La:S) doped with Er3+ are presented and discussed. Emission and absorption spectra and lifetimes of energy levels have been measured. The 2.7 μm emission of Er3+ has been observed from chalcogenide glass for the first time. Radiative and non-radiative transition rates are calculated and compared with the measured lifetimes of interesting energy levels. Comparing this glass with Er3+-doped silica glasses, it is shown that the absorption and emission cross-sections of Er3+-doped Ga:La:S are around 2.5 times higher, radiative transition rates are around five times higher due to its higher refractive index, while multiphonon non-radiative decay rates are around three orders lower due to its much lower phonon energy. Furthermore, the inverse energy transfer process in Er3+:Ga:La:S glass may have significant implications for the operation of Er3+:Ga:La:S devices. These spectral properties, along with the higher solubility for rare earth-ions in Ga:La:S, make this glass a good candidate for new applications.

Infrared emission from holmium doped gallium lanthanum sulphide glass

Infrared emission at 1.2, 1.25, 1.67, 2.0, 2.2, 2.9, 3.9, and 4.9µm is measured in holmium (Ho3+) doped gallium lanthanum sulphide (GLS) glass. Branching ratios, radiative quantum efficiencies, and emission cross sections are calculated from lifetime, absorption, and emission measurements using Judd-Ofelt analysis and the Fuchtbauer-Ladenburg equation. The fluorescence band at 3.9µm coincides with an atmospheric transmission window and the fluorescence band at 4.9µm overlaps with the fundamental absorption of carbon monoxide, making the glass a potential fibre laser source for remote sensing and gas sensing applications. This is the first time this latter transition has been reported in any holmium doped host.

Spectroscopy of potential mid-infrared laser transitions in gallium lanthanum sulphide glass

This paper presents experimental results on the mid-infrared emission of rare-earth doped gallium lanthanum sulphide glasses and fibres. Measured fluorescence includes the 3.4 µm transition (1G4 to 3F4) in Pr3+-doped Ga:La:S fibre, the 3.6 µm transition (4F(9/2) to 4I(9/2)) in Er3+- doped Ga:La:S fibre, and the 4.3 µm transition ( 6H(11/2) to 6H(13/2) ) in Dy3+-doped Ga:La:S bulk glass. Fibre lasers with these emission wavelengths would be of interest for gas sensing applications.

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.

Spectroscopic and Thermal Properties of GeS2-based chalcohalide glasses

Abstract The low phonon energy of germanium sulphide glasses makes them ideal candidates as hosts for 1·3 μm fibre amplifier applications. However, the GeS2 glass host suffers from a major drawback of poor rare-earth ion solubility. In an efficient device, the solubility of Pr ions has to be enhanced, without adversely affecting either the thermal or the spectroscopic properties of the glass. In the present investigation, we report the synthesis and optical properties of modified GeS2-based chalcohalide glasses with excellent thermal characteristics suitable for drawing low-loss optical fibres.

Cadmium mixed halide glass for optical amplification at 1.3 μm

Optical and spectroscopic data and calculations in support of an efficient 1.3 µm amplifier in Pr3+-doped cadmium mixed halide glass host are presented. We find that the dominant parameter affecting the amplifier gain is the lifetime (325 µm) of the Pr3+-1G4 state. The long lifetime is the direct consequence of a decreased multiphonon decay rate in this low-phonon-energy glass host. We predict gain in excess of 30 dB for 100 mW pumping in low loss fibres, and for background loss of 1 dB/m, gain figures are as high as 15-20 dB.

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.

Effects of impurities in cadmium halide glasses for 1.3 μm amplifier

Abstract Cadmium mixed halide glasses have been recently identified as a potential low-phonon energy host for a 1.3 μm Pr 3+ -doped optical fibre amplifier. The crystallization behaviour of the mixed halide glasses while reheated above their glass transition temperature is reported. The effect of impurities in the starting raw materials on the quality of the bulk glass is reported. The OH − absorption was monitored by Fourier transform infrared spectrometry, and related to the lifetime of the 1 G 4 excited state in Pr 3+ -doped glass. The thermal stability of the glass was studied using heat treatment data obtained by a differential scanning calorimeter.