PHOTOINDUCED CHARGE EFFECTS IN K0.984LI0.016TAO3

Photoinduced effects were studied in K0.984Li0.016TaO3. making use of birefringence and second-harmonic generation as probes of structural m odifications induced by illumination at 2.4 eV. It is shown that photo induced charges have no direct influence on the size and orientational freedom of polar microregions. Quenching of the polar order by illumi nation is only observed in the presence of an external field and it is consistent with the build-up of a depoling field, owing to space-char ge formation. Light of energy below 2 eV is not effective by itself, b ut it can be if the sample is pre-sensitized with photons of higher en ergy.