▎ 摘　　要

A quantum theory of third-harmonic generation in graphene is presented. An analytical formula for the nonlinear conductivity tensor sigma((3))(alpha beta gamma delta)(omega,omega,omega) is derived. Resonant maxima of the third harmonic are shown to exist at low frequencies omega << E-F/h, as well as around the frequency omega = 2E(F)/h, where E-F is the Fermi energy in graphene. At an input power of a CO2 laser (lambda approximate to 10 mu m) of about 1 MW/cm(2), the output power of the third harmonic (lambda approximate to 3.3 mu m) is expected to be similar or equal to 50 W/cm(2).