Three-dimensional optical memory using glasses as a recording medium through a multi-photon absorption process

;The feasibility of multilayered optical data storage was examined in SiO2 and Ge-SiO2 grasses by using a focused 800 nm, 120 fs, 200 kHz pulsed laser. The glasses are transparent in the wavelengths ranging from 300 to 1000 nm. After the irradiation with the 800 nm tightly focused femtosecond laser. a refractive-index bit was formed in the glasses. The relationships between the size of refractive-index bit versus average power and irradiation duration of the laser pulse have been examined. ESR spectra showed a significant increase in the concentration of SiE' and GeE' color centers in the laser irradiated glasses. Writing 3-dimensional refractive-index bit inside the transparent glasses based on a multi-photon absorption process is expected to become a useful method used to fabricate optical memory with both an ultra-high storage density and an ultra-high recording speed.