Time reversal of Berry's phase by optical phase conjugation

We examine experimentally the time-reversal properties of Berry's geometrical phase in one of its optical manifestations, Pancharatnam's phase, through the use of optical phase conjugation. The time-reversal symmetry of the total optical system is broken by a nonreciprocal element, a Faraday rotator. Nevertheless, we find that the geometrical part of the phase acquired by an optical wave in passing through the system still respects time-reversal invariance.