“…The properties of mid-infrared (MIR) transparency, high refractive index, low phonon energy, high optical non-linearity (Zakery and Elliott 2003), and an ability to doped them with rare-earth element ions (Sanghera and Aggarwal 1999;Sanghera et al 2009;Tang et al 2015;Falconi et al 2016), make chalcogenide glasses attractive for use in planar photonic integrated circuits (Seddon et al 2006Abdel-Moneim et al 2015), and narrow-and broad-band fibre-based laser sources (Petersen et al 2014) and amplifiers (Hu et al 2015;Falconi et al 2017) for the MIR. Although much research effort has been paid to the development and characterisation of chalcogenide glasses for photonics, relatively little refractive index dispersion data are presently available at MIR wavelengths, see for example: Orava et al (2009), Qiao et al (2011), Dantanarayana et al (2014), Gleason et al (2016), Wang et al (2017) and references therein.…”