Infrared emission and ion-ion interactions in thulium and terbium doped gallium lanthanum sulphide glass

Abstract

Infrared emission at 0.7, 0.8, 1.2, 1.5, 1.8, 2.3, 3.8, and 4.8µm is measured in thulium (Tm³⁺) and terbium (Tb³⁺) doped gallium lanthanum sulphide (GLS) glass. Emission cross sections are calculated from the absorption and emission spectra using Judd-Ofelt analysis, the Füchtbauer-Ladenburg equation, and the theory of McCumber. Fluorescence and lifetime measurements confirm energy transfer from Tm³⁺ to Tb³⁺ ions and reveal a number of new cross-relaxation/upconversion processes between Tm³⁺ ions involving the ³F_2,3 and ³H₅ levels that can only be observed in low phonon energy materials. These processes indicate that the most efficient pump wavelength for the 1.2µm and 3.8µm transitions is 0.7µm. The Tm³⁺ fluorescence at 3.8µm coincides with an atmospheric transmission window and the Tb³⁺ fluorescence at 4.8µm overlaps with the fundamental absorption of carbon monoxide, making the glass a potential fibre laser source for remote sensing and gas sensing applications.

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Identifiers

ORCID for W.S. Brocklesby: orcid.org/0000-0002-2123-6712

ORCID for D.W. Hewak: orcid.org/0000-0002-2093-5773

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