Diffraction grating-based encoded particle

1. An encoded particle, comprising:

a particle 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 within said single material at a grating location, said refractive index variation comprising a plurality of refractive index pitches superimposed at said grating location; and

said grating providing an output optical signal indicative of a code when illuminated by an incident light signal propagating from outside said substrate, said output optical signal being a result of passive, non-resonant scattering from said grating when illuminated by said incident light signal.

2. The apparatus of claim 1 , wherein said substrate is made of a material selected from the group: glass, silica, plastic, rubber, and polymer.

3. The apparatus of claim 1 , wherein said code comprises a plurality of digital bits.

4. 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.

5. The apparatus of claim 1 , wherein said code comprises a plurality of bits, each bit having a plurality of states.

6. The apparatus of claim 1 , wherein said code comprises a plurality of bits, each bit having a corresponding spatial location 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.

7. The apparatus of claim 6 , wherein the value of each bit corresponds to the magnitude of refractive index variation of a corresponding refractive index pitch in said grating.

8. The apparatus of claim 1 , wherein said code comprises a plurality of digital bits, each bit having a corresponding spatial location 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.

9. The apparatus of claim 8 , wherein the value of each bit corresponds to the presence or absence of a corresponding refractive index pitch in said grating.

10. The apparatus of claim 1 , wherein said incident light signal comprises a substantially single wavelength.

11. The apparatus of claim 1 , wherein said incident light signal comprises a plurality of wavelengths or a single wavelength scanned over a predetermined wavelength range.

12. The apparatus of claim 11 , 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.

13. The apparatus of claim 12 , wherein the value of each bit corresponds to the magnitude of refractive index variation of a corresponding refractive index pitch in said grating.

14. The apparatus of claim 11 , 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.

15. The apparatus of claim 14 , wherein the value of each bit corresponds to the presence or absence of a corresponding refractive index pitch in said grating.

16. The apparatus of claim 1 , wherein said substrate has a length that is less than a predetermined value, said value being about 30, 65, 80, 125, 250, 500, 750 or 1000 microns.

17. The apparatus of claim 1 , wherein said substrate has a diameter that is less than a predetermined value, said value being about 30, 65, 80, 125, 250, 500, 750 or 1000 microns.

18. The apparatus of claim 1 , wherein said substrate has a reflective coating disposed thereon.

19. 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.

20. 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.

21. The apparatus of claim 1 , wherein said substrate has a magnetic or electric charge polarization.

22. The apparatus of claim 1 , wherein said substrate has geometry having holes therein or protruding sections therein.

23. 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.

24. 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.

25. 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.

26. 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.

27. 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.

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 grating region has a refractive index that is not greater than that of said non-grating region.

29. The apparatus of claim 1 , wherein said incident light signal is incident on said substrate along a longitudinal grating axis of said grating.

30. The apparatus of claim 1 , wherein said incident light signal is incident on said substrate at an angle to a longitudinal grating axis of said grating.

31. The apparatus of claim 1 , wherein said grating is a thin grating or a blazed grating.

32. The apparatus of claim 1 , wherein said substrate comprises a plurality of said gratings.

33. The apparatus of claim 1 , wherein said substrate comprises a plurality of said gratings each at different locations within said substrate.

34. The apparatus of claim 1 , wherein said incident light signal comprises laser light.

35. The apparatus of claim 1 , wherein said substrate is photosensitive at least at said grating location.

36. A method of reading an encoded particle, comprising:

obtaining 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 within said single material at a grating location, said refractive index variation comprising a plurality of refractive index pitches superimposed at said grating location;

illuminating said substrate with an incident light signal propagating from outside said substrate, said substrate providing an output optical signal indicative of a code, said output optical signal being a result of passive, non-resonant scattering from said grating when illuminated by said incident light signal; and

reading said output optical signal and detecting said code therefrom.

37. The method of claim 36 , wherein said substrate is made of a material selected from the group: glass, silica, plastic, rubber, and polymer.

38. The method of claim 36 , wherein said code comprises a plurality of digital bits.

39. The method of claim 36 , 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.

40. The method of claim 36 , wherein said code comprises a plurality of bits, each bit having a plurality of states.

41. The method of claim 36 , wherein said code comprises a plurality of bits, each bit having a corresponding spatial location 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.

42. The method of claim 41 , wherein the value of each bit corresponds to the magnitude of refractive index variation of a corresponding refractive index pitch in said grating.

43. The method of claim 36 , wherein said code comprises a plurality of digital bits, each bit having a corresponding spatial location 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.

44. The method of claim 43 , wherein the value of each bit corresponds to the presence or absence of a corresponding refractive index pitch in said grating.

45. The method of claim 36 , wherein said incident light signal comprises a substantially single wavelength.

46. The method of claim 36 , wherein said incident light signal comprises a plurality of wavelengths or a single wavelength scanned over a predetermined wavelength range.

47. The method of claim 46 , 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.

48. The method of claim 47 , wherein the value of each bit corresponds to the magnitude of refractive index variation of a corresponding refractive index pitch in said grating.

49. The method of claim 46 , 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.

50. The method of claim 49 , wherein the value of each bit corresponds to the presence or absence of a corresponding refractive index pitch in said grating.

51. The method of claim 36 , wherein said substrate has a length that is less than a predetermined value, said value being about 30, 65, 80, 125, 250, 500, 750 or 1000 microns.

52. The method of claim 36 , wherein said substrate has a diameter that is less than a predetermined value, said value being about 30, 65, 80, 125, 250, 500, 750 or 1000 microns.

53. The method at claim 36 , wherein said substrate has a reflective coating disposed thereon.

54. The method of claim 36 , 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.

55. The method of claim 36 , wherein said substrate has a coating material disposed on at least a portion of said substrate, said coating comprising a polymer.

56. The method of claim 36 , wherein said substrate has a magnetic or electric charge polarization.

57. The method of claim 36 , wherein said substrate has geometry having holes therein or protruding sections therein.

58. The method of claim 36 , 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, arid polygon.

59. The method of claim 36 , 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.

60. The method of claim 36 , 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.

61. The method of claim 36 , 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.

62. The method of claim 36 , 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.

63. The method of claim 36 , 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.

64. The method of claim 36 , wherein said incident light signal is incident on said substrate along a longitudinal grating axis of said grating.

65. The method of claim 36 , wherein said incident light signal is incident on said substrate at an angle to a longitudinal grating axis of said grating.

66. The method of claim 36 , wherein said grating is a thin grating or a blazed grating.

67. The method of claim 36 , wherein said substrate comprises a plurality of said gratings.

68. The method of claim 36 , wherein said substrate comprises a plurality of said gratings each at different locations within said substrate.

69. The method of claim 36 , wherein said incident light signal comprises laser light.

70. The method of claim 36 , wherein said substrate is photosensitive at least at said grating location.