Room-temperature Near-infrared Excitonic Lasing from Mechanically Exfoliated InSe Microflake

The development of chip-level near-infrared laser sources using two-dimensional semiconductors is imperative to maintain the architecture of van der Waals integrated optical interconnections. However, the established two-dimensional semiconductor lasers may have either the disadvantages of poor controllability of monolayered gain media, large optical losses on silicon, or complicated fabrication of external optical microcavities. This study demonstrates room-temperature near-infrared lasing from mechanically exfoliated γ-phase indium selenide (InSe) microflakes free from external optical microcavities at a center wavelength of ∼1030 nm. The lasing action occurs at the sub-Mott density level and is generated by exciton-exciton scattering with a high net modal optical gain of ∼1029 cm^-1. Moreover, the lasing is sustained for microdisks fabricated by a simple laser printing with a reduced threshold. These results suggest that InSe is a promising material for near-infrared microlasers and can be employed in a wide range of applications, including imaging, sensing, and optical interconnects.