NONRECIPROCITY OF NATURAL ROTATORY POWER

We have observed that a light beam that passed through an optically ac tive crystal of Bi12SiO20 and that was then reflected exactly back thr ough it did not recover its initial polarization orientation. The nonr eciprocal component of the rotation was of the order of 2 x 10(-3) of the reciprocal, single-pass rotation. This nonreciprocity is unambiguo us evidence of broken reversality of the light-matter interaction proc ess. (C) 1996 Optical Society of America.