  The electro-optic Kerr effect in cholesteric blue phase liquid crystals is
known to occur on sub-millisecond time scales, which is much faster than
director reorientation in nematic liquid crystals. Using two-beam interference
microscopy, we report the presence of a very slow response in the Kerr effect,
with a characteristic time of several seconds or more. Using a simplified model
for the reorientation dynamics, we attribute the slow response to the coupling
between the local director reorientation and field-induced deformation of the
lattice. We provide evidence for our argument by showing that the slow response
can be removed by inhibiting lattice deformation through polymer stabilization.
