Room temperature mid-infrared fiber lasing beyond 5  µm in chalcogenide glass small-core step index fiber

This Letter, to the best of our knowledge, reports mid-infrared fiber lasing beyond 5 µm at room temperature for the first time, Ce³⁺-doped, chalcogenide glass, step index fiber employed in-band pumping with a 4.15 µm quantum cascade laser. The lasing fiber is was 64 mm long, with a calculated numerical aperture of 0.48 at the lasing wavelengths. The core glass was Ge₁₅As₂₁Ga₁Se₆₃ atomic % (at. %), doped with 500 parts-per-million-by-weight Ce, with a 9 µm core diameter. The cladding glass was Ge₂₁Sb₁₀Se₆₉ at. % with a 190 µm outer diameter. As pump power increases continuous wave lasing corresponding to the ²F_7/2→²F_5/2, transition in the Ce³⁺ ion occurs at 5.14 µm, 5.17 µm, and 5.28 µm.