Index and density changes induced by proton radiation in lanthanum crown glass

We studied the refractive index and density changes in cerium-doped lanthan um crown glass irradiated in air with 38.5 MeV protons. At a low proton flu ence, the index change is linear with dose, and reaches 2.4x10(-5) at 2.7x1 0(12) p/cm(2) (0.65 Mrad dose). The rate of index change decreases with the proton fluence, but at high total dose (10(14) p/cm(2)) radiation-induced surface dilatation and birefringence start to appear. Our results show that the present concept of radiation-hard optical glass should be revised and that a high dose of proton radiation can produce index changes sufficient f or the fabrication of integrated optical devices. (C) 2001 American Institu te of Physics.