Three-dimensional optical storage inside a silica glass by using a focused femtosecond pulsed laser

We report on three-dimensional optical data storage inside a silica glass by using a focused 800 nm, 120 fs, 200 kHz pulsed laser. The glass is transparent in the wavelengths ranging from 250 to 1000 nm, After the irradiation of the 800 nm tightly focused femtosecond laser, a refractive-index bit was formed in the glass. The relations between the size of refractive-index bit versus average power and irradiation duration of the laser;pulse have been examined. Absorption and ESR spectra showed a significant increase in the concentration of SiE' color centers in the laser irradiated glass. A multi-photon absorption process is considered to have occurred in the glasses when irradiated by the laser pulses, We suggest that writing three-dimensional refractive-index bit inside the transparent glasses based on a multi-photon absorption process will become a promising method to fabricate optical memory with both an ultrahigh storage density and an ultrahigh recording speed. (C) 1998 Elsevier Science B.V. All rights reserved.