Multilayered optical bit storage in Sm(DBM)₃phen-doped poly(methyl methacrylate) read out by fluorescence and reflection modes

We report on multilayer optical data storage using Sm(DBM)3Phen-doped poly(methyl methacrylate) and a tightly focused 800 nm, 1 kHz, 100 fs pulsed laser. After pulsed femtosecond laser irradiation, refractive-index change and a visible fluorescent bit were formed at the irradiated position inside the bulk sample. The photoluminescence should result from the ligands peeled from the central Sm³⁺ ions via bond scission induced by laser irradiation. Multilayer patterns recorded by tightly focusing the pulsed laser beam were read out by a reflection-type fluorescence confocal microscope, which can detect the scattered signal and also the fluorescent signal of the stored bits. The dependence of fluorescence and scattering signals on recording pulse energy was examined. The signal-to-noise ratios via two retrieval modes were compared as a function of recording depth. The detection of the fluorescence signal enables retrieval of the stored bits with a higher S/N ratio.