Patent ID: 8335099

Claim:
A memory device comprising: a substrate containing a phase change material having phases comprising amorphous and crystalline phases, the phase change material having optical properties that change depending on whether the phase change material is in the amorphous phase or the crystalline phase; means for generating light and transmitting the light into the substrate; means for causing the phase change material to change between the amorphous and crystalline phases thereof by operating the light generating means to generate light pulses that pass into the substrate at an amplitude and pulse width sufficient to change the phase of the phase change material between the amorphous phase and the crystalline phase within regions of the substrate; at least one optical sensing device adapted to detect light from the light generating means that passes into the phase change material to the optical sensing device and generate electrical signals based thereon; and means for converting the electrical signals into bit values according to their level relative to a predetermined threshold.