Applied Physics

Flash Memory

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Science  14 Jul 2000:
Vol. 289, Issue 5477, pp. 217
DOI: 10.1126/science.289.5477.217a

In CDs and DVDs information is stored in a single plane, but the use of stacked planes within an optically writable material offers the opportunity to attain information storage densities some two orders of magnitude greater. Stacked memories have relied so far on sophisticated confocal optics for writing and reading, both of which are somewhat limited by cross talk between adjacent planes. Watanabe et al. report a simpler technique that is based on observing photoluminescence from photomodified regions in silica, which allows them to use just a single objective lens for the writing and read-out processes. High-powered 120-femtosecond laser pulses at 800 nm create a defective region (the bit or voxel) about 1.4 μm in diameter via multiphoton absorption. Illumination with the same wavelength light, but at much lower intensity, makes the voxel photoluminesce. Cross talk between bit planes is also suppressed, so that bit planes only 3 μm apart can be resolved. — ISO

Appl. Phys. Lett. 77, 13 (2000).

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