Multilayered optical bit memory with a high signal-to-noise ratio in fluorescent polymethylmethacrylate

We report on the three-dimensional optical memory utilizing a photoluminescence (PL) change in polymethylmethacrylate. Irradiation with a femtosecond pulsed laser (800 nm, 1 kHz, 100 fs) induced a strong PL spectrum in the visible range, which may result from the photogeneration of emissive radicals. Multilayered patterns were recorded inside the bulk sample by tightly focusing a pulsed laser beam. The pattern images were read out by a reflection-type fluorescent confocal microscope which detected the blue-green emission at 410–510 nm. The stored bits were retrieved with a high signal-to-noise ratio in the absence of any cross-talk.