We present an overview of rare-earth doped heavy metal oxide and oxy-fluoride glasses which show promise as host
materials for lasers operating in the 2-5 μm spectral region for medical, military and sensing applications. By
engineering glass composition and purity, tellurite and germanate glasses can support transmission up to and beyond 5
μm and can have favourable thermal, mechanical and environmental stability compared to fluoride glasses. We discuss
techniques for glass purification and water removal for enhanced infrared transmission. By comparing the material
properties of the glass, and spectroscopic performance of selected rare-earth dopant ions we can identify promising
compositions for fibre and bulk lasers in the mid-infrared. Tellurite glass has recently been demonstrated to be a suitable
host material for efficient and compact lasers in the ~2 μm spectral region in fibre and bulk form and the next challenge
is to extend the operating range further into the infrared region where silica fibre is not sufficiently transparent, and
provide an alternative to fluoride glass and fibre.
|