  Dove prisms and K-mirrors are devices extensively used for rotating the
wavefront of an optical field. These devices have several applications,
including measurement of orbital angular momentum, microscopy, beam steering
and pattern recognition. However, the wavefront rotation achieved through these
devices is always accompanied by polarization changes in the incident field,
which is an undesirable feature in many of these applications. Although the
polarization changes induced by a Dove prism have been explored to quite some
extent, no such study is available for a K-mirror. In this letter, we
theoretically and experimentally investigate polarization changes induced in
the transmitted field by a rotating K-mirror. For quantifying such polarization
changes, we define a quantity, mean polarization change D, which ranges from 0
to {\pi}. We find that K-mirrors can reduce D to about 0.03{\pi}, for any
incident state of polarization; however, reducing D to the same extent with a
Dove prism is practically unviable. Therefore, K-mirrors are better
alternatives to Dove prisms in applications in which the polarization changes
accompanying wavefront rotation need to be minimum.
