All-Chalcogenide Ring Fiber Laser

We demonstrate the first all-chalcogenide Brillouin fiber laser as well as the first all-chalcogenide ring cavity laser. The compact device comprises two engineered components: an As2Se3 optical fiber coupler combined to an As2S3 amplifying fiber. While the coupler simultaneously enables insertion of pump light, extraction of laser light, and the formation of a ring cavity, the amplifying fiber provides nonlinear gain to ensure laser oscillation. Thanks to the strong Brillouin gain of As2S3, only 3 m of amplifying fiber is required, thus making a resonant cavity with a free spectral range significantly larger than the Brillouin gain spectrum. The laser therefore naturally enables single longitudinal mode operation without additional filtering device. Acting as a coherence enhancing component, the resulting Brillouin laser benefits of a linewidth reduction factor of 7 with respect to the pump laser. Finally, this laser design is compatible with a broad range of wavelengths that spreads from 1.55 µm up to 8 µm, thanks to its all-chalcogenide structure.