  Blazars are highly variable active galactic nuclei which emit radiation at
all wavelengths from radio to gamma-rays. Polarized radiation from blazars is
one key piece of evidence for synchrotron radiation at low energies and it also
varies dramatically. The polarization of blazars is of interest for
understanding the origin, confinement, and propagation of jets. However, even
though numerous measurements have been performed, the mechanisms behind jet
creation, composition and variability are still debated. We performed
simultaneous gamma-ray and optical photopolarimetry observations of 45 blazars
between Jul. 2008 and Dec. 2014 to investigate the mechanisms of variability
and search for a basic relation between the several subclasses of blazars. We
identify a correlation between the maximum degree of optical linear
polarization and the gamma-ray luminosity or the ratio of gamma-ray to optical
fluxes. Since the maximum polarization degree depends on the condition of the
magnetic field (chaotic or ordered), this result implies a systematic
difference in the intrinsic alignment of magnetic fields in pc-scale
relativistic jets between different types blazars (FSRQs vs. BL Lacs), and
consequently between different types of radio galaxies (FR Is vs. FR IIs).
