Visible upconversion in rare-earth doped gallium lanthanum sulphide based glasses

Abstract

Chalcogenide glasses are usually known for their good infrared and poor visible transparency which limit their applications to passive and active devices in the infrared wavelength region. Gallium lanthanum sulphide glasses, however, show visible transparency down to 500nm. The low phonon energy of the glass increases the radiative quantum efficiency of rare-earth energy levels compared to commonly used fluorozirconate glasses and provides long-lived intermediate levels for efficient two-step excitation to visible energy levels. Green and red upconversion emission has been observed in Pr³⁺, Nd³⁺, Ho³⁺, and Er³⁺ doped glasses under Ti:sapphire pumping in wavelengths regions where diode laser sources are easily available. Lifetime measurements reveal the excitation process is either excited-state absorption or upconversion caused by ion-ion interactions. Modification of the glass with lanthanum oxide or caesium chloride improves the visible transparency and shifts the UV absorption edge to 450nm and 400nm, respectively, and also improves the fibre drawing of these glasses.

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Identifiers

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

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

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