ULTRAVIOLET-INDUCED DISTRIBUTED-FEEDBACK GRATINGS IN CE-3+-DOPED SILICA OPTICAL FIBERS

Nondegenerate four-wave mixing was used to write permanent distributed-feedback refractive-index gratings in a Ce3+-doped (80 parts in 10(6)), aluminosilicate, single-mode glass optical fiber at 300 K with a corresponding change in the refractive index DELTA-n = 2.5 x 10(-5) at 808 nm. Direct excitation of the 2F5/2-5d transition at 292 nm results in the photoionization of Ce3+ and the creation of color centers. The photoinduced absorption recovered on wavelength-dependent time scales ranging from seconds to hours. Below approximately 450 nm the recovery was incomplete, which contributed to the observed refractive-index change.