High density optically encoded information storage using second harmonic generation in silicate glasses
OwnerNabil M. Lawandyinventor
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Abstract
Multiple bits of information are stored in the frequency domain in a bulk glass using optically encoded .chi..sup.(2) gratings. The information is read out by measuring a second harmonic generation (SHG) from the encoded glass as a function of wavelength. Information storage densities in excess of 10.sup.8 bits/cm.sup.2 are readily achievable. The stored information is stable under readout conditions, and the information can be erased and rewritten.
Claims20
An information storage medium comprising a body having a plurality of regions each of which is capable of being encoded with multiple units of information, each of said regions of said body being responsive to electromagnetic radiation having at least one first wavelength for outputting electromagnetic radiation at a second wavelength that is shorter than the first wavelength for indicating a presence of at least one stored encoded unit of information.
A method for storing information, comprising the steps of:
- providing a storage medium that is comprised of glass;
- storing a first unit of information within a predetermined region of the medium by simultaneously applying a first wavelength and a second wavelength that is one half of the first wavelength;
- and
- storing a second unit of information within the same predetermined region of the medium by simultaneously applying a third wavelength and a fourth wavelength that is one half of the third wavelength.
A method for storing data within a storage medium, comprising the steps of:
- providing an n-bit data word, where n is equal to or greater than one;
- providing an optical source capable of outputting n different wavelengths and the second harmonic of each of the n different wavelengths;
- selectively writing or not writing a .chi..sup.(2) grating within a region of a glass-based medium for each bit of the n-bit word as a function of a value of each bit, the step of writing, for a given one of the bits, including a step of simultaneously applying to the region at least one of the predetermined ones of the n wavelengths and the second harmonic;
- and
- subsequently reading-out the n-bit data word from the glass-based medium by the steps of applying the n different wavelengths to the predetermined region and detecting the presence of corresponding ones, if any, of the second harmonics that are generated by an associated .chi..sup.(2) grating within the region in response to the application of the n different wavelengths.
A method for reading information from an information storage medium, comprising the steps of:
- illuminating a region of the information storage medium with electromagnetic radiation having n fundamental wavelengths, where n is equal to or greater than one;
- and
- detecting up to n second harmonic wavelengths that are generated within the illuminated region in response to the step of illuminating, each detected second harmonic wavelength representing information that is stored within the storage medium.
A structure for storing information, comprising:
- a plurality of waveguides individual ones of which contain a material which is capable of being encoded at a plurality of regions with multiple units of information, each of said regions of said material being responsive to electromagnetic radiation having at least one first wavelength for outputting electromagnetic radiation at a second wavelength that is shorter than the first wavelength for indicating encoded information, wherein at least the outputted electromagnetic radiation having the second wavelength is guided by the waveguide that contains the material.
Dependencies are inferred from the claim text.