Optical birefringence imaging of x-ray excited lithium tantalate

X-ray absorption in lithium tantalate induces large, long-lived (∼10(−5) s) optical birefringence, visualized via scanning optical polarimetry. Similar birefringence measured from glass, sapphire, and quartz was two orders of magnitude weaker; much of this reduction can be accounted for by their smaller cross section for x-ray absorption. While x-ray induced charges can perturb local refractive indices and lead to birefringence, aligned dipoles in the non-centrosymmetric unit cell of ferroelectric LiTaO(3) create electric fields that also induce birefringence via electro-optic coupling, which shows up as a dependence on crystal orientation. Time-resolved measurements from LiTaO(3) show a prompt response on a picosecond time scale, which along with the long decay time suggest novel opportunities for optical detection of x-rays.