Optical single-bit recording and fluorescent readout utilizing aluminum oxide single crystals

• US 20030235136A1
• Filed: 04/22/2003
• Published: 12/25/2003
• Est. Priority Date: 12/04/2001
• Status: Active Grant

• Current Assignee: Landauer, Inc. (Fortive Corp.)
• Original Assignee: Landauer, Inc. (Fortive Corp.)
• Inventors: Orlov, Sergei S., Akselrod, Mark
• Granted Patent: US 7,072,275 B2
• Time in Patent Office: Days
• US Class Current: 369/108
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: C30B 15/00 Single-crystal growth by pulling from a melt, e.g. Czochralski method under a protective fluid C30B27/00
• CPC Class Codes: C30B 15/04 adding doping materials, e.g. for n-p-junction
• CPC Class Codes: C30B 29/20 Aluminium oxides
• CPC Class Codes: G11B 2007/0009 for carriers having data stored in three dimensions, e.g. volume storage
• CPC Class Codes: G11B 2007/2431 group 13 elements (B, Al, Ga, In)
• CPC Class Codes: G11B 2007/2432 Oxygen
• CPC Class Codes: G11B 7/00455 involving reflectivity, absorption or colour changes
• CPC Class Codes: G11B 7/0052 involving reflectivity, absorption or colour changes
• CPC Class Codes: G11B 7/00552 involving colour change media
• CPC Class Codes: G11B 7/13922 passive
• CPC Class Codes: G11B 7/14 specially adapted to record on, or to reproduce from, more than one track simultaneously
• CPC Class Codes: G11B 7/24088 for storing more than two values, i.e. multi-valued recording for data or prepits
• CPC Class Codes: G11B 7/243 comprising inorganic materials only, e.g. ablative layers

Abstract

The present invention provides methods and apparatuses for writing information to, reading information from, and erasing information on a luminescent data storage medium comprising Al₂O₃. The method includes writing and erasing of the information using photo ionization via sequential two-photon absorption and non-destructive reading the information using fluorescent detection. The apparatuses for writing and reading the information incorporate confocal detection and spherical aberration correction for multilayer volumetric fluorescent data storage. The methods also allow multilevel recording and readout of information for increased storage capacity.

Claims

1. A method of writing information to a data storage medium comprising the steps of:

providing a luminescent data storage medium comprising Al₂O₃; and

writing said information to said luminescent data storage medium with an optical source.

2. The method of claim 1, wherein said information is written to said luminescent data storage medium by using a two-photon absorption technique and a photo-ionization technique resulting in removal of an electron from a color center in said luminescent data storage medium and moving said electron to a thermally stable trap in said luminescent data storage medium.

3. The method of claim 2, wherein said two-photon absorption technique is a sequential two-step two-photon absorption technique.

4. The method of claim 2, wherein said two-photon absorption technique is a simultaneous direct two-photon absorption without intermediate levels.

5. The method of claim 1, wherein said luminescent data storage medium is written to in more than one layer at the different depths inside said data storage medium.

6. The method of claim 5, wherein said optical source emits a laser beam from an optical read/write head and said optical read/write head incorporating spherical aberration compensation with a diffraction limited depth of at least 10 microns.

7. The method of claim 1, wherein said luminescent data storage medium is written to at different modulation depths thereby achieving multilevel data storage.

8. The method of claim 1, wherein said luminescent data storage medium comprises:

a base material comprising Al₂O₃;

a first dopant comprising Mg; and

a second dopant comprising carbon, wherein said luminescent data storage medium includes a plurality of at least one type of oxygen vacancy defect.

9. The method of claim 8, wherein said luminescent data storage medium includes at least one color center having:

an absorption in the region of 435±

5 nm, an emission in the region of 520±

5 nm and a 9±

3 ns fluorescence lifetime.

10. The method of claim 8, wherein said luminescent data storage medium includes at least one color center having:

an absorption in the region of 335±

5 nm, an emission in the region of 750±

5 nm and a 80±

10 ns fluorescence lifetime.

11. The method of claim 8, wherein said luminescent data storage medium includes at least one color center having:

an absorption in the region of 435±

5 nm, an emission in the region of 520±

5 nm and a 9±

3 ns fluorescence lifetime and at least one color center having;

an absorption in the region of 335+5 nm, an emission in the region of 750±

5 nm and a 80±

10 ns lifetime.

12. The method of claim 8, wherein said luminescent data storage medium is written for a write time based on a change in fluorescence amplitude of at least 1%.

13. The method of claim 8, wherein said laser beam has a wavelength of 370 to 490 nm, inclusive.

14. The method of claim 8, wherein said optical source emits a laser beam having a wavelength of 390 nm.

15. The method of claim 8, wherein said optical source emits a laser beam having a write time in the range of 0.1 ps to 1 ms.

16. The method of claim 8, wherein said optical source emits a laser beam having has a write time of 10 ns.

17. The method of claim 1, wherein at least part of the said luminescent data storage medium is a single crystal Al₂O₃ material.

18. The method of claim 1, further comprising the step of:

focusing said optical source to a predetermined depth in said luminescent data storage medium.

19. The method of claim 18, wherein said optical source is focused by moving said luminescent data storage medium with respect to said optical source.

20. The method of claim 18, wherein said laser beam is focused on said luminescent data storage medium by adjusting the position of an optical pick-up head containing said optical source.

21. The method of claim 1, further comprising the step of:

moving said luminescent data storage medium to a write position prior to said laser beam writing to said luminescent data storage medium.

22. The method of claim 1, wherein said optical source emits a laser beam having a power density of greater than 10³ W/cm².

23. The method of claim 1, wherein said optical source emits a laser beam having a power density of at least 10⁵ W/cm².

24. A method of reading information stored on a data storage medium comprising the steps of:

(a) exciting a luminescent data storage medium with an optical source to thereby cause said luminescent data storage medium to emit a fluorescent light signal, wherein said luminescent data storage medium comprises Al₂O₃ and wherein said optical source emits a read laser beam having a wavelength in the range of an absorption band of said luminescent data storage medium; and

(b) measuring said laser induced fluorescence light signal from said luminescent data storage medium, to thereby read said information stored on said luminescent data storage medium.

25. The method of claim 24, wherein step (a) comprises exciting said luminescent data storage medium using a one-photon absorption technique without causing photo-ionization of the storage centers to thereby cause said luminescent data storage medium to emit a fluorescent light signal and thereby read said luminescent data storage medium nondestructively.

26. The method of claim 24, wherein step (a) comprises exciting said luminescent data storage medium using a simultaneous two-photon absorption technique without causing photo-ionization of the storage centers to thereby cause said luminescent data storage medium to emit a fluorescent light signal and thereby read said luminescent data storage medium non-destructively.

27. The method of claim 26, wherein said data storage medium is excited by light from said optical source having a wavelength about two times longer than the wavelength of the absorption band of the said luminescent data storage medium.

28. The method of claim 24, wherein said luminescent data storage medium comprises:

a base material comprising Al₂O₃;

a first dopant comprising magnesium; and

a second dopant comprising carbon, wherein said luminescent data storage medium includes a plurality of at least one type of oxygen vacancy defect.

29. The method of claim 28, wherein said luminescent data storage medium includes at least one color center having:

an absorption in the region of 435±

5 nm, an emission in the region of 520±

5 nm and a 9±

3 ns fluorescence lifetime.

30. The method of claim 28, wherein said luminescent data storage medium includes at least one color center having:

an absorption in the region of 335±

5 nm, an emission in the region of 750±

5 nm and a 80±

10 ns lifetime.

31. The method of claim 28, wherein said read laser beam has a wavelength within an absorption band of Al₂O₃:

C,Mg centered at 335±

10 nm and wherein said fluorescent light signal has an emission band having a wavelength range of 620-880 nm, inclusive, and being centered at 750±

10 nm.

32. The method of claim 28, wherein said fluorescent light signal is excited using light of the wavelength within an absorption band of Al₂O₃:

C,Mg and centered at 255±

10 nm and wherein said fluorescent light signal has an emission band having a wavelength range of 620 nm to 880 nm, inclusive, and being centered at 750±

10 nm.

33. The method of claim 28, wherein said luminescent data storage medium includes at least one color center having:

an absorption in the region of 435±

5 nm, an emission in the region of 520±

5 nm and a 9±

3 ns fluorescence lifetime and at least one color center having;

an absorption in the region of 335±

5 nm, an emission in the region of 750+5 nm and a 80±

10 ns lifetime.

38. The method of claim 28, wherein fluorescent light signal has a wavelength of 470 and 580 nm, inclusive, and centered at 520±

10 nm.

39. The method of claim 28, wherein said read laser beam illuminates said luminescent data storage medium for the period of time between 1 ns and 10 μ

s.

40. The method of claim 28, wherein said read laser beam illuminates said luminescent data storage medium for about 100 ns.

41. The method of claim 28, wherein said laser beam has a read time of 0.1 ps to 1 s, inclusive.

42. The method of claim 28, wherein said laser beam has a read time of 10 ns

43. The method of claim 28, wherein prior to step (a) said method further comprises the step of:

writing to said luminescent data storage medium with a write laser beam.

44. The method of claim 28, wherein said read and write laser beams have a wavelength of 380 to 490 nm, inclusive.

45. The method of claim 44, wherein said read laser beam has a wavelength longer than said write laser beam and said read laser beam has a wavelength of about 430 to 490 nm, inclusive.

46. The method of claim 24, wherein information from said luminescent data storage medium is read from more than one layer at the different depths inside said luminescent data storage medium.

47. The method of claim 46, wherein step (b) comprises detecting said fluorescence signal using a confocal detection technique.

48. The method of claim 46, wherein said read laser beam is emitted by said optical source disposed in a read/write head and said optical read/write head incorporates spherical aberration compensation allowing for a diffraction limited spot at a depth of at least 10 microns.

49. The method of claim 24, wherein prior to step (a) said method further comprises the step of:

writing to said luminescent data storage medium with a write laser beam.

50. The method of claim 49, wherein said read and write laser beams have the same wavelength.

51. The method of claim 49, wherein said read and write laser beams have different wavelengths.

52. The method of claim 49, wherein said read and write laser beams are each focused through a lens and said lens is used for writing information to and reading information from said luminescent data storage medium.

53. The method of claim 24, further comprising the step of:

moving said luminescent data storage medium with respect to said optical source and to a read position prior to said read laser beam exciting said luminescent data storage medium.

54. The method of claim 24, further comprising the step of:

focusing said read laser beam to a predetermined depth in said luminescent data storage medium.

55. The method of claim 54, wherein said read laser beam is focused by moving said luminescent data storage medium with respect to said read laser beam.

56. The method of claim 54, wherein said read laser beam is focused by adjusting the position of an optical pick-up head containing said optical source.

57. The method of claim 24, wherein said luminescent data storage medium is read for a read time equal to a read laser beam pulse length and wherein said luminescent data storage medium is a stationary data storage medium.

58. The method of claim 24, wherein said luminescent data storage medium is read for a read time equal to a ratio of a reading spot size with respect to the velocity of said luminescent data storage medium and wherein said luminescent data storage medium is a moving data storage medium.

59. The method of claim 24, wherein said read laser beam has a power density that is less than about 10³ W/cm².

60. A method of erasing information stored on a data storage medium comprising the steps of:

(a) providing a luminescent data storage medium comprising Al₂O₃, said luminescent data storage medium having said information stored thereon; and

(b) illuminating said luminescent data storage medium with an optical source to thereby erase said information.

61. The method of claim 60, wherein said information is erased from said data storage medium using a two-photon absorption technique.

62. The method of claim 60, wherein said luminescent data storage medium comprises:

a base material comprising Al₂O₃;

a first dopant comprising magnesium; and

a second dopant comprising carbon, wherein said luminescent data storage medium includes a plurality of at least one type of oxygen vacancy defect.

63. The method of claim 62, wherein said luminescent data storage medium includes at least one color center having:

an absorption in the region of 435±

5 nm, an emission in the region of 520±

5 nm and a 9±

3 ns fluorescence lifetime and at least one color center having;

an absorption in the region of 335±

5 nm, an emission in the region of 750±

5 nm and a 80±

10 ns lifetime.

64. The method of claim 63, wherein step (b) comprises illuminating of said luminescent data storage medium with said optical source having a wavelength at 335±

30 nm and a power density above the threshold of two-photon absorption at 10³ W/cm².

65. The method of claim 64, wherein said illumination is accomplished with said optical source having a wavelength at 335±

30 and is performed after illuminating said luminescent data storage medium with UV light having a wavelength centered at 205±

30 nm.

66. The method of claim 65, wherein said UV light is coherent.

67. The method of claim 65, wherein said UV light is incoherent.

68. An apparatus comprising:

a luminescent data storage medium comprising Al₂O₃; and

an optical source for writing information to said luminescent data storage medium.

69. An apparatus comprising:

a luminescent data storage medium comprising Al₂O₃;

a first optical source for exciting said luminescent data storage medium to thereby cause said luminescent data storage medium to emit a fluorescent light signal when information is stored on said luminescent data storage medium; and

measuring means for measuring said emitted fluorescent light signal.

70. The apparatus of claim 69, further comprising:

a second optical source for writing information to said luminescent data storage medium.

71. The apparatus of claim 70, wherein said first and second optical sources are the same.

72. The apparatus of claim 71, wherein said measuring means include a confocal detection means.

73. The apparatus of claim 70, further comprising an optical head including said first optical source and said second optical source.

74. An apparatus comprising:

a luminescent data storage medium comprising Al₂O₃;

an optical source for writing information to said luminescent data storage medium; and

.

compensation means for adaptive spherical aberration compensation of said optical source to allow for diffraction limited spot optical addressing with a depth range of at least 10 microns.

75. An apparatus comprising:

a luminescent data storage medium comprising Al₂O₃; and

writing means for writing information to said luminescent data storage medium by using a two-photon absorption technique and a photo-ionization technique resulting in removal of an electron from a color center in said luminescent data storage medium and moving said electron to a thermally stable trap in said luminescent data storage medium, said writing means comprising a first optical source.

76. The apparatus of claim 75, further comprising:

reading means for exciting said luminescent data storage medium with an optical source having a wavelength in the range of an absorption band of said luminescent data storage medium to thereby cause said luminescent data storage medium to emit a fluorescent light signal via one-photon absorption without photo-ionization of color centers in said luminescent data storage medium, said reading means including a second optical source; and

means for measuring said emitted fluorescent light signal.

77. The apparatus of claim 76, wherein said first and second optical sources are the same.