  A cyclotron resonance maser source using low-effective-mass conduction
electrons in graphene, if successful, would allow for generation of Far
Infrared (FIR) and Terahertz (THz) radiation without requiring magnetic fields
running into the tens of Tesla. In order to investigate this possibility, we
consider a situation in which electrons are effectively injected via pumping
from the valence band to the conduction band using an infrared (IR) laser
source, subsequently gyrate in a magnetic field applied perpendicular to the
plane of the graphene, and give rise to gain for a FIR/THz wave crossing the
plane of the graphene. The treatment is classical, and includes on equal
footing the electron interation with the radiation field and the decay in
electron energy due to collisional processes. A set of integral expressions is
derived by assuming that the non-radiative energy loss processes of the
electrons can be adequately represented by a damping force proportional and
antiparallel to their momentum. Gain is found even though there is no inversion
of the energy distribution function. Gain can occur for electron damping times
as short as hundreds of femtoseconds.
