A group of chalcogenide glass is particularly functional as lens, filter and window operating in the long-wavelength infrared range from 8 μm to 12 μm. The transmission window of prototypical Ge-Sb-Se glass, for example, normally spans from ∼1 μm to ∼15 μm, being transparent also in the near- and mid-infrared wavelengths. Based on our experimental results performed in an effort to augment the potential of chalcogenide glass for use in the long-wavelength infrared range, it is verified that its transmission window, as exemplified with Ge-Sb-Se glass in this study, is adjustable via doping of some rare earth and/or transition metal ions. Specifically, a notch-type absorption is introduced at mid-infrared wavelengths by rare earth ions such as Ce3+, Nd3+, Pr3+ and Tb3+, whereas transition metal ion like Fe2+ brings about a relatively broadband absorption. A spectral lineshape potentially suitable for the bandpass filter applications in the long-wavelength infrared range is demonstrated through co-doping of Ce3+ and Fe2+ ions.
