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.

Modeling of resonantly pumped mid-infrared Pr3+-doped chalcogenide fiber amplifier with different pumping schemes

We propose a model for resonantly pumped Pr³⁺-doped chalcogenide fiber amplifiers, which includes excited state absorption and the full spectral amplified spontaneous emission spanning from 2 μm to 6 μm. Based on this model, the observed near- and mid-infrared photoluminescence generated from Pr³⁺-doped chalcogenide fiber is explained. Then the output properties of a 4.1 μm resonantly pumped Pr³⁺-doped chalcogenide fiber amplifier are simulated in both co- and counter-pumping schemes. Results show that the 4.1 μm counter-pumped fiber amplifier can achieve a power conversion efficiency (PCE) of over 62.8% for signal wavelengths ranging from 4.5 μm to 5.3 μm. This is, to our best knowledge, the highest simulated PCE for a Pr³⁺-doped chalcogenide fiber amplifier.

Theoretical study of population inversion in active doped MIR chalcogenide glass fibre lasers (invited)

We study the mechanism of the population inversion in mid-infrared fibre lasers based on a chalcogenide glass host doped with active lanthanide ions. Three lanthanide dopant ions are considered: terbium, dysprosium and praseodymium. We predict the relevant trivalent ion level populations and gain. The simulation parameters were obtained by fabricating and optically characterising a series of trivalent ion doped chalcogenide glass samples. We also provide simple analytical expressions that aid the design of the cascade lasing process.

Superior photoluminescence (PL) of Pr³⁺-In, compared to Pr³⁺-Ga, selenide-chalcogenide bulk glasses and PL of optically-clad fiber

The photoluminescent-(PL)-properties of Pr³⁺-ions in indium-containing selenide-chalcogenide bulk-glasses are found to be superior when compared with gallium-containing analogues. We observe circa doubling of mid-infrared (MIR) PL intensity from 3.5 to 6 μm for bulk glasses, pumped at 1.55 μm wavelength, and an increased excited state lifetime at 4.7 μm. PL is reported in optically-clad fiber. Ga addition is well known to enhance RE³⁺ solubility and PL behavior, and is believed to form ([RE³⁺]-Se-[Ga(III)]) in the glasses. Indium has the same outer electronic-structure as gallium for solvating the RE-ions. Moreover, indium is heavier and promotes lower phonon energy locally around the RE-ion, thereby enhancing the RE-ion PL behavior, as observed here.