In the context of the major problems linked to global warming and pollution, a micro-sensor based on mid-infrared spectroscopy could be a useful tool for the continuous measurement of various bio-chemical species that are disrupting our environment. With the aim of developing a mid-infrared source potentially integrated into a micro-sensor, we have fabricated rare-earth-doped chalcogenide thin films using various physical vapor deposition techniques [1]. Rare-earth-doped amorphous chalcogenide films play a motivating role in the development of integrated planar optical circuits. Initially, amorphous Ga-Ge-Sb-S sulfide thin films doped with dysprosium or thulium were prepared by pulsed laser deposition and radio-frequency magnetron sputtering, respectively. The results revealed promising prospects, reinforced by the clear observation of near-infrared photo-luminescence of $\mathrm{Dy}^{3+}$ and $\mathrm{Tm}^{3+}$ doped sulfide films. RF magnetron sputtering and pulsed laser deposition were then studied in the case of Erbium doping in order to optimize deposition parameters, showing near-IR and mid-IR emissions at $1.55 \ \mu \mathrm{m}\left({ }^{4} \mathrm{I}_{13 / 2} \rightarrow{ }^{4} \mathrm{I}_{15 / 2}\right)$ and at $2.8 \ \mu \mathrm{m}\left({ }^{4} \mathrm{I}_{11 / 2} \rightarrow{ }^{4} \mathrm{I}_{13 / 2}\right)$. Finally, in view of these initial mid-IR results, selenide thin films doped with praseodymium or dysprosium were deposited by radio-frequency (RF) magnetron sputtering in an attempt to luminesce further into the mid-IR. Mid-IR guided photoluminescence of $\mathrm{Dy}^{3+}$ or $\mathrm{Pr}^{3+}$ at wavelengths up to $5.5 \ \mu \mathrm{m}$ was first demonstrated at room temperature using co-propagating pumping at near-IR wavelengths for ridge structures displaying single-mode propagation at mid-IR wavelengths [2]. The luminescence properties of the waveguides are then studied as a function of rare-earth concentration and Ar pressure. In addition to the Ga-Ge-Sb-Se host matrix, the In-Ge-Sb-Se matrix has also been successfully studied. Based on this on-chip emission, CO 2 detection around $4.3 \ \mu \mathrm{m}$ has also been performed