  We have theoretically demonstrated the emission of circularly-polarized
terahertz (THz) waves from intrinsic Josephson junctions (IJJs) which is
locally heated by an external heat source such as the laser irradiation. We
focus on a mesa-structured IJJ whose geometry is slightly deviate from a square
and find that the local heating make it possible to emit circularly-polarized
THz waves. In this mesa, the inhomogeneity of critical current density induced
by the local heating excites the electromagnetic cavity modes TM (1,0) and TM
(0,1), whose polarizations are orthogonal to each other. The mixture of these
modes results in the generation of circularly-polarized THz waves. We also show
that the circular polarization dramatically changes with the applied voltage.
The emitter based on IJJs can emit circularly-polarized and continuum THz waves
by the local heating, and will be useful for various technological application.
