  In laser gravitational waves detectors optical loss restricts sensitivity. We
discuss polarization scattering as one more possible mechanism of optical
losses. Circulated inside interferometer light is polarized and after
reflection its plane of polarization can turn a little due to reflecting
coating of mirror can have slightly different refraction index along axes $x,\,
y$ in plane of mirror surface (optical anisotropy). This anisotropy can be
produced during manufacture of coating (elasto-optic effect). This orthogonal
polarized light, enhanced in cavity, produces polarization optical loss.
Polarization map of mirrors is very important and we propose to measure it.
Polarization loss can be important in different precision optical experiments
based on usage of polarized light, for example, in quantum speed meter.
