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A method and apparatus for labeling an item using diffraction grating-based encoded optical identification elements 8 includes an optical substrate 10 having at least one diffraction grating 12 disposed therein. The grating 12 has one or more colocated pitches Λ which represent a unique identif

A method and apparatus for labeling an item using diffraction grating-based encoded optical identification elements 8 includes an optical substrate 10 having at least one diffraction grating 12 disposed therein. The grating 12 has one or more colocated pitches Λ which represent a unique identification digital code that is detected when illuminated by incident light 24 . The incident light 24 may be directed transversely from the side of the substrate 10 (or from an end) with a narrow band (single wavelength) or multiple wavelength source, and the code is represented by a spatial distribution of light or a wavelength spectrum, respectively, or a combination thereof. The element 8 can provide a large number of unique codes, e.g., greater than 67 million codes, and can withstand harsh environments. The encoded element 8 may be used to label any desired item, such as large or small objects, products, solids, powders, liquids, gases, plants, minerals, cells and/or animals, or any combination of or portion of one or more thereof. The label may be used for many different purposes, such as for sorting, tracking, identification, verification, authentication, anti-theft/anti-counterfeit, security/anti-terrorism, or for other purposes. In a manufacturing environment, the elements 8 may be used to track inventory for production information or sales of goods/products.

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What is claimed is: 1. An optical identification element for identifying an item, comprising: a substrate, at least a portion of said substrate being made of a substantially single material and having at least one diffraction grating embedded therein, said grating having a resultant refractive vari

What is claimed is: 1. An optical identification element for identifying an item, comprising: a substrate, at least a portion of said substrate being made of a substantially single material and having at least one diffraction grating embedded therein, said grating having a resultant refractive variation within the substantially single material at a grating location; said grating providing an output optical signal indicative of a code when illuminated by an incident light signal propagating from outside the substrate, said output signal being a result of passive, non-resonant scattering from said grating when illuminated by said incident light signal; and the element being at least partially disposed on the item. 2. The apparatus of claim 1 wherein said refractive index variation comprises at least one refractive index pitch superimposed at said grating location. 3. The apparatus of claim 1 wherein said refractive index variation comprises a plurality of refractive index pitches superimposed at said grating location. 4. The apparatus of claim 1 wherein said substrate is made of a material selected from the group: glass, silica, plastic, rubber, and polymer. 5. The apparatus of claim 1 wherein said code comprises a plurality of digital bits. 6. The apparatus of claim 1 wherein said code comprises at least a predetermined number of bits, said number being: 3, 5, 7, 9, 10, 12, 14, 16, 18, 20, 24, 28, 30, 40, 50, or 100. 7. The apparatus of claim 1 wherein said code comprises a plurality of bits, each bit having a plurality of states. 8. The apparatus of claim 1 wherein said code comprises a plurality of bits, each bit having a corresponding spatial location in said optical output signal and each bit in said code having a value related to the intensity of said output optical signal at the spatial location of each bit. 9. The apparatus of claim 8 wherein the value of said intensity is related to the magnitude of refractive index variation of a corresponding refractive index pitch in said grating. 10. The apparatus of claim 1 wherein said code comprises a plurality of digital bits, each bit having a corresponding spatial location in said optical output signal and each bit in said code having a binary value related to the intensity of said output optical signal at the spatial location of each bit. 11. The apparatus of claim 10 wherein the value of each bit is related to the presence or absence of a corresponding refractive index pitch in said grating. 12. The apparatus of claim 1 wherein said incident light comprises a single wavelength. 13. The apparatus of claim 1 wherein said incident light comprises a plurality of wavelengths or a single wavelength scanned over a predetermined wavelength range. 14. The apparatus of claim 13 wherein said code comprises a plurality of bits, and each bit in said code having a value related to the intensity of said output optical signal at a wavelength corresponding to each bit. 15. The apparatus of claim 14 wherein the value of said intensity is related to the magnitude of refractive index variation of a corresponding refractive index pitch in said grating. 16. The apparatus of claim 13 wherein said code comprises a plurality of digital bits, and each bit in said code having a binary value related to the intensity of said output optical signal at the wavelength corresponding to each bit. 17. The apparatus of claim 16 wherein the value of each bit is related to the presence or absence of a corresponding refractive index pitch in said grating. 18. The apparatus of claim 1 wherein said substrate has a length that is less than about 1000 microns. 19. The apparatus of claim 1 wherein said substrate has a diameter that is less than about 1000 microns. 20. The apparatus of claim 1 wherein said substrate has a reflective coating disposed thereon. 21. The apparatus of claim 1 wherein said substrate has a coating disposed on at least a portion of said substrate, at least a portion of said coating being made of a material that allows sufficient amount of said incident light signal to pass through said material to allow detection of said code. 22. The apparatus of claim 1 wherein said substrate has a coating material disposed on at least a portion of said substrate, said coating comprising a polymer. 23. The apparatus of claim 1 wherein said substrate has a magnetic or electric charge polarization. 24. The apparatus of claim 1 wherein said substrate has geometry having holes therein or having protruding sections therein. 25. The apparatus of claim 1 wherein at least a portion of said substrate has an end cross sectional geometry selected from the group: circular, square, rectangular, elliptical, clam-shell, D-shaped, and polygon. 26. The apparatus of claim 1 wherein at least a portion of said substrate has a side view geometry selected from the group: circular, square, rectangular, elliptical, clam-shell, D-shaped, and polygon. 27. The apparatus of claim 1 wherein at least a portion of said substrate has a 3-D shape selected from the group: a cylinder, a sphere, a cube, and a pyramid. 28. The apparatus of claim 1 wherein said substrate has a grating region where said grating is located and a non-grating region where said grating is not located; and wherein said substrate has a plurality of grating regions. 29. The apparatus of claim 1 wherein said substrate has a grating region where said grating is located and a non-grating region where said grating is not located; and wherein said grating region has a refractive index that is greater than that of said non-grating region. 30. The apparatus of claim 1 wherein said substrate has a grating region where said grating is located and a non-grating region where said grating is not located; and wherein said grating region has a refractive index that is not greater than that of said non-grating region. 31. The apparatus of claim 1 wherein said incident light is incident on said substrate along a longitudinal grating axis of said grating. 32. The apparatus of claim 1 wherein said incident light is incident on said substrate at an angle to a longitudinal grating axis of said grating. 33. The apparatus of claim 1 wherein said incident light comprises laser light. 34. The apparatus of claim 1 wherein said grating comprises a thin grating or a blazed grating. 35. The apparatus of claim 1 wherein said substrate comprises a plurality of said gratings. 36. The apparatus of claim 1 wherein said substrate comprises a plurality of said gratings each at different locations within said substrate. 37. The apparatus of claim 1 wherein said substrate comprises a particle or bead. 38. The apparatus of claim 1 wherein at least a portion of said substrate is disposed on an outer surface of the item. 39. The apparatus of claim 1 wherein said substrate is disposed within said item and said item is made of a material that allows said code to be detected from output signal. 40. The apparatus of claim 1, where the item is selected from the group, comprising: large or small objects, products, solids, powders, liquids, gases, plants, currency, ID cards, minerals, cells and/or animals. 41. The apparatus of claim 1, where said code comprises a digital code indicative of information relating to: identity, type of item, lot number, manufacturer, serial number, date code, or code error checking. 42. The optical identification element of claim 1, wherein said code identifying at least one of the element and said item. 43. An item having an optical identification element disposed therein, comprising: a substrate, at least a portion of said substrate being made of a substantially single material and having at least one diffraction grating embedded therein, said grating having a resultant refractive index variation with the substantially single material at a grating location; said grating providing an output optical signal indicative of a code when illuminated by an incident light signal propagating from outside the substrate, said code identifying at least one of the element and said item, said output signal being a result of passive, non-resonant scattering from said grating when illuminated by said incident light signal; and said code identifying the item. 44. The apparatus of claim 43 wherein said refractive index variation comprises at least one refractive index pitch superimposed at said grating location. 45. The apparatus of claim 43 wherein said refractive index variation comprises a plurality of refractive index pitches superimposed at said grating location. 46. The apparatus of claim 43 wherein said substrate comprises a particle or bead. 47. The apparatus of claim 43, where the item is selected from the group, comprising: large or small objects, products, solids, powders, liquids, gases, plants, currency, ID cards, minerals, cells and/or animals. 48. The apparatus of claim 43, where said code comprises a digital code indicative of information relating to: identity, type of item, lot number, manufacturer, serial number, date code, or code error checking. 49. A method of reading a code associated with an optical identification element that is disposed on an item, the element having a substrate, at least a portion of said substrate being made of a substantially single material and having a diffraction grating embedded therein, said grating having a resultant refractive index variation within the substantially single material at a grating location, comprising: illuminating said element with incident light propagating from outside the substrate, said grating providing an output light signal indicative of the code, said output signal being a result of passive, non-resonant scattering from said grating when illuminated by said incident light signal; and reading said output light signal and detecting said code therefrom. 50. The method of claim 49 wherein said refractive index variation comprises at least one refractive index pitch superimposed at said grating location. 51. The method of claim 49 wherein said refractive index variation comprises a plurality of refractive index pitches superimposed at said grating location. 52. The method of claim 49 wherein said element comprises a particle or bead. 53. The method of claim 49, where the item is selected from the group, comprising: large or small objects, products, solids, powders, liquids, gases, plants, currency, ID cards, minerals, cells and/or animals. 54. The method of claim 49, where said code comprises a digital code indicative of information relating to: identity, type of item, lot number, manufacturer, serial number, date code, or code error checking. 55. The method of claim 49, wherein said code identifying at least one of the element and said item. 56. A method for labeling an item, comprising: obtaining a substrate having at least a portion thereof being made of a substantially single material and having at least one diffraction grating embedded therein, said grating having a resultant refractive variation with the substantially single material at a grating location, said grating providing an output optical signal indicative of a code when illuminated by an incident light signal propagating from outside the substrate, said output signal being a result of passive, non-resonant scattering from said grating when illuminated by said incident light signal; and said substrate being at least partially disposed on the item. 57. The meted of claim 56 wherein said refractive index variation comprises at least one refractive index pitch superimposed at said grating location. 58. The apparatus of claim 56 wherein said retroactive index variation comprises a plurality of refractive index pitches superimposed at said grating location. 59. The method of claim 56 wherein said substrate is disposed within said item. 60. The method of claim 56 wherein said substrate comprises a particle or bead. 61. The method of claim 56, where the item is selected from the group, comprising: large or small objects, products, solids, powders, liquids, gases, plants, currency, ID cards, minerals, cells and/or animals. 62. The method of claim 56, where said code comprises a digital code indicative of information relating to: identity, type of item, lot number, manufacturer, serial number, date code, or code error checking. 63. The method of claim 56, wherein said code identifying at least one of the element and said item.