“…Due to its structure, GaSe shows fascinating optoelectronic properties, including photoresponse in ultraviolet–visible (UV–vis) spectral range (from 1.8 to 5 eV), nonlinear optical behavior, and a distinctive spin physics (e.g., spin‐orbit coupling effects and generation/retention of spin polarization under nonresonant optical pumping). For the aforementioned properties, GaSe has been proposed for photodetectors with high responsivity (e.g., up to values > 1000 A W −1 at light intensity ≤ 0.1 mW cm −2 , in heterojunction with graphene), nonlinear frequency generation (e.g., second and third harmonic and ultrabroadband radiation generation), spin polarization control (e.g., spintronic logic devices), light‐emitting devices, optical microcavities, and saturable absorbers . Moreover, the number of layers and strain engineering strongly affect the GaSe optoelectronic properties, which can be on‐demand tailored to fulfill the requirements of the final applications .…”