Semiconductor optical memory device for optical storage of information with increased recording density

An optical information storage system, comprising:

• tunable light source means supplied with a write command signal for producing a first optical beam with a wavelength selected from a range of wavelengths in response to the write command signal;
• continuous light source means supplied with a read command signal for producing a second optical beam having a continuous spectrum in said range of wavelengths;
• a semiconductor optical memory device provided to be irradiated by the first optical beam of the tunable light source means and by the second optical beam of the continuous light source means, said semiconductor optical memory device comprising:
• a semiconductor layer having an upper major surface and a lower major surface, said semiconductor layer extending in first and second, mutually perpendicular directions, said semiconductor layer being formed with a plurality of elemental recording areas each having a size generally equal to the wavelength of the first optical beam;
• and
• a plurality of quantized regions formed in said each elemental recording area of said semiconductor layer, each of said quantized regions having first and second sizes in said first and second directions respectively, each said quantized region further having a third size in a third direction perpendicular to any of said first and second directions, at least two of said first through third sizes being set sufficiently small in each said quantized region such that a quantized energy level is formed in each said quantized region as a result of confinement of the sizes of said quantized region, each said quantized region thereby absorbing an optical radiation of which wavelength is pertinent to the quantized energy level of that quantized region by forming first type carriers having a first polarity and second type carriers having a second, opposing polarity, each of said quantized regions comprising a semiconductor material confined in at least two mutually perpendicular directions to form said quantized energy level;
• each of the plurality of quantized regions in said each elemental recording area having the optical absorption wavelength that is different from that of other quantized regions included in the same elemental recording area;
• each of said quantized regions being separated from the other quantized regions, with respect to the directions in which the size of the quantized region are limited, by a semiconductor material that has a band gap larger than that of the semiconductor material forming the quantized region;
• and
• photodetection means provided to receive the optical beam produced by the continuous light source means and passed through the semiconductor optical memory device for detecting the wavelength of the received optical beam.