▎ 摘　　要

We propose a novel nanospaser that operates in the mid-infrared region and utilizes a nanopatch of graphene as its plasmonic core and a quantum-well cascade as its gain medium. This design takes advantage of the low optical losses in graphene resulting from its high electron mobility. The proposed quantum cascade graphene spaser generates optical fields with unprecedentedly high nanolocalization, which is characteristic of graphene plasmons. This spaser will be an efficient nanosource of intense and coherent hot-spot fields in the mid-infrared spectral region with potential widespread applications in mid-infrared nanoscopy, nanospectroscopy, nanolithography, and optoelectronic information processing.