  We probe the spectropolarimetric properties of the black-hole binary source
4U 1630$-$47 in the steep power law state. We detect a significant polarization
fraction of $\sim$7 % at a polarization angle of $\sim$21 $^\circ$. The $2-12$
keV NICER spectrum can be fitted with a combination of a thermal and a
Comptonization component, the latter characterized by a spectral index, $\Gamma
\sim$2.1, along with a reflection feature at $\sim$7.0 keV. In the $2-8$ keV
band, the degree of polarization of 4U 1630$-$47 in the steep power law state
is 4.4 $\sigma$ different from the value previously measured in the high soft
state. In the steep power law state, the polarization fraction increases as a
function of energy but exhibits an overall drop in each energy band compared to
that of the high soft state. We propose that the decrease in the polarization
fraction in the steep power law state could be attributed to the presence of a
corona. The observed polarization properties in both states can be explained by
the self-irradiation of the disk around a Kerr black hole, likely influenced by
the frame-dragging effect.
