ULTRAVIOLET-INDUCED PERMANENT BRAGG GRATINGS IN CERIUM-DOPED ZBLAN GLASSES OR OPTICAL FIBERS

A holographic method was used to write refractive-index gratings in ZB LAN fluoroziroconate glasses or fibers doped by a Ce concentration of 5000 or 10,000 parts-in-10(6) weight. Direct pumping of the F-2(5/2)-5 d transitions of Ce3+ ions near 245 nm resulted in a change in the ref ractive index. The photoinduced change partly recovered on a time scal e of several hours at room temperature. The remaining change in the re fractive index looked stable on a time scale of a month. This permanen t change reaches 2 x 10(-5) at 1560 nm.