  In this work, we study the efficiency of charging a quantum battery through
optical pumping. The battery consists of a qutrit and it is connected to a
natural thermal reservoir and an external coherent drive in the limit where its
upper energy level can be adiabatically eliminated from the dynamics. In this
scenario, the drive plus spontaneous emission optically pumps the intermediate
energy level of the qutrit and the battery can be understood as being charged
by an effective higher temperature reservoir that takes it out of equilibrium
with the natural reservoir and stores useful energy in it. We also analyse the
efficiency of using this battery and charging scheme as the work fluid of a
two-stroke thermal machine. The thermal machine includes a fourth level through
which work is extracted from the battery via a unitary transformation,
therefore setting the limit of maximum efficiency of the machine.
