  The underlying plasma composition of relativistic extragalactic jets remains
largely unknown. Relativistic magnetohydrodynamic (RMHD) models are able to
reproduce many of the observed macroscopic features of these outflows. The
nonthermal synchrotron emission detected by very long baseline interferometric
(VLBI) arrays, however, is a by-product of the kinetic-scale physics occurring
within the jet, physics that is not modeled directly in most RMHD codes. This
paper attempts to discern the radiative differences between distinct plasma
compositions within relativistic jets using small-scale 3D relativistic
particle-in-cell (PIC) simulations. We generate full Stokes imaging of two PIC
jet simulations, one in which the jet is composed of an electron-proton
($e^{-}$-$p^{+}$) plasma (i.e., a normal plasma jet), and the other in which
the jet is composed of an electron-positron ($e^{-}$-$e^{+}$) plasma (i.e., a
pair plasma jet). We examined the differences in the morphology and intensity
of the linear polarization (LP) and circular polarization (CP) emanating from
these two jet simulations. We find that the fractional level of CP emanating
from the $e^{-}$-$p^{+}$ plasma jet is orders of magnitude larger than the
level emanating from an $e^{-}$-$e^{+}$ plasma jet of a similar speed and
magnetic field strength. In addition, we find that the morphology of both the
linearly and circularly polarized synchrotron emission is distinct between the
two jet compositions. We also demonstrate the importance of slow-light
interpolation and we highlight the effect that a finite light-crossing time has
on the resultant polarization when ray-tracing through relativistic plasma.
