Photo-induced gratings in thin color center layers on lithium fluoride.
We study the recording of permanent Bragg gratings on surface-colored lithium fluoride (LiF) crystals by using the interference pattern of a continuous-wave UV argon-ion laser operating at 244 nm. Gratings with spatial periodicity ranging from 400 to 1000 nm are written by using a phase-mask interferometer and are stable for several months after the writing process. Absorption and photoluminescence spectra show the bleaching of primary F and F -aggregate laser-active color centers as a result of the process. Confocal microscopy is used to determine the pitch and the profile of the fluorescent gratings. The UV laser-induced optical bleaching in highly colored LiF ultrathin layers is responsible for the periodic spatial modulation of absorption and photoemission properties that characterize the gratings. In the colored surface layer, a reduction of as much as 50% of the initial color-center-induced refractive-index increase has been estimated in the bleached areas.
Bonfigli
Francesca
F
Department of Physical Technologies and New Materials, ENEA, Frascati Research Center,via Enrico Fermi 45, 00044 Frascati (RM), Italy.
Vincenti
Maria Aurora
MA
Almaviva
Salvatore
S
Montereali
Rosa Maria
RM
Nichelatti
Enrico
E
Nogueira
Rogério N
RN
Kalinowski
Hypolito José
HJ