3-DIMENSIONAL OPTICAL STORAGE INSIDE TRANSPARENT MATERIALS

We present a novel method for three-dimensional optical data storage t hat has submicrometer size resolution, provides a large contrast in in dex of refraction, and is applicable to a wide range of transparent ma terials. Bits are recorded by use of a 0.65-N.A objective to focus 100 -fs laser pulses inside the material. The laser pulse produces a submi crometer-diameter structurally altered region with high contrast in in dex of refraction. We record binary information by writing such bits i n multiple planes and read it out with a microscope objective with a s hort depth of field. We demonstrate data storage and retrieval with 2- mu m in-plane bit spacing and 15-mu m interplane spacing (17 Gbits/cm( 3)). Scanning electron microscopy and atomic force microscopy show str uctural changes confined to an area 200 nn in diameter. (C) 1996 Optic al Society of America.