BROADBAND METAMATERIAL APPARATUS, METHODS, SYSTEMS, AND COMPUTER READABLE MEDIA

• US 20100225562A1
• Filed: 01/15/2010
• Published: 09/09/2010
• Est. Priority Date: 01/15/2009
• Status: Active Grant

• Current Assignee: Duke University
• Original Assignee: Duke University
• Inventors: Smith, David R.
• Granted Patent: US 9,971,063 B2
• Time in Patent Office: Days
• US Class Current: 343/909
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: G02B 1/007 made of negative effective refractive index materials
• CPC Class Codes: H01Q 15/02 Refracting or diffracting devices, e.g. lens, prism

Abstract

Broadband metamaterial apparatus, methods, systems, and computer readable media are disclosed, as well as exemplary embodiments that provide cloaking, beam steering, and beam focusing. In one exemplary implementation, a broadband interface structure has a front surface region and a back surface region. The broadband interface structure is arranged to provide electromagnetic energy characteristic of an apparent profile of the back surface region substantially different than an actual profile of the back surface region for electromagnetic energy received at the front surface region.

Claims

1. An apparatus, comprising:

a broadband interface structure having a front surface region and a back surface region, the broadband interface structure being arranged to provide electromagnetic energy characteristic of an apparent profile of the back surface region substantially different than an actual profile of the back surface region for electromagnetic energy received at the front surface region.

2. The apparatus of claim 1, further comprising:

an electromagnetic reflector positioned adjacent to the back surface region.

3. The apparatus of claim 1, wherein the actual profile is a substantially nonplanar profile and the apparent profile is a substantially planar profile.

4. The apparatus of claim 1, wherein the actual profile is a first substantially nonplanar profile and the apparent profile is a second substantially nonplanar profile different than the first substantially nonplanar profile.

5. The apparatus of claim 1, wherein the broadband interface structure includes an impedance matching layer positioned at least partially within the front surface region, the impedance matching layer being substantially nonreflective of electromagnetic energy received at the front surface region.

6. The apparatus of claim 5, wherein the impedance matching layer is characterized by an effective refractive index that gradiently approaches unity at an exterior surface of the impedance matching layer.

7. The apparatus of claim 1, wherein the broadband interface structure is characterized by an effective refractive index that is not less than one.

8. The apparatus of claim 7, where the effective refractive index is substantially isotropic in two dimensions.

9. The apparatus of claim 7, where the effective refractive index is substantially isotropic in three dimensions.

10. The apparatus of claim 7, wherein the effective refractive index is substantially constant over a broadband frequency range.

11. The apparatus of claim 10, wherein the broadband frequency range is a microwave frequency range.

12. The apparatus of claim 10, wherein the broadband frequency range is an optical frequency range.

13. The apparatus of claim 10, wherein the effective refractive index is a spatially-varying effective refractive index.

14. The apparatus of claim 13, wherein the broadband interface structure includes a plurality of nonresonant elements having respective individual electromagnetic responses, the plurality of respective individual electromagnetic responses substantially providing the effective refractive index.

15. The apparatus of claim 14, where the nonresonant elements have varied respective physical parameters corresponding to varied respective individual electromagnetic responses, and the plurality of varied respective individual electromagnetic responses provides the spatially-varying effective refractive index.

16. The apparatus of claim 15, wherein the nonresonant elements include I-shaped conducting elements and the varied respective physical parameters include geometrical parameters of the I-shaped conducting elements.

17. The apparatus of claim 15, wherein the nonresonant elements include closed-ring conducting elements and the varied respective physical parameters include geometrical parameters of the closed-ring conducting elements.

18. The apparatus of claim 17, wherein the closed-ring conducting elements are substantially square closed-ring conducting elements.

19. The apparatus of claim 15, wherein the nonresonant elements include conducting elements defining capacitive gaps and the varied respective physical parameters include capacitances of the capacitive gaps.

20. The apparatus of claim 15, wherein the nonresonant elements include inductive-capacitive elements having inductive-capacitive resonance frequencies that substantially exceed the broadband frequency range, and the varied respective physical parameters include impedances of the inductive-capacitive elements.

21. The apparatus of claim 20, wherein the impedances include capacitances.

22. The apparatus of claim 20, wherein the impedances include inductances.

23. The apparatus of claim 20, wherein the impedances include resistances.

24. A method, comprising:

receiving broadband electromagnetic energy from one or more directions;

directing the broadband electromagnetic energy toward a physical topography; and

substantially independently of the one or more directions, transmitting the broadband electromagnetic energy in a manner whereby the transmitted broadband electromagnetic energy appears to be returned from an apparent topography different than the physical topography.

25. The method of claim 24, wherein the receiving is substantially non-reflectively receiving.

26. The method of claim 24, wherein the transmitting is substantially non-reflectively transmitting.

27. The method of claim 24, wherein the broadband electromagnetic energy is microwave electromagnetic energy.

28. The method of claim 24, wherein the broadband electromagnetic energy is radiowave electromagnetic energy.

29. The method of claim 24, wherein the broadband electromagnetic energy is optical electromagnetic energy.

30. An electromagnetic apparatus, comprising:

a plurality of non-resonant elements having respective individual electromagnetic responses, the plurality of respective electromagnetic responses providing effective medium parameters;

where the effective medium parameters include an effective permittivity that is substantially non-constant over a broadband frequency range, an effective permeability that is substantially non-constant over the broadband frequency range, and an effective refractive index that is substantially constant over the broadband frequency range.

31. An electromagnetic apparatus, comprising:

a plurality of non-resonant elements having respective individual electromagnetic responses, the plurality of respective electromagnetic responses providing effective medium parameters;

where the effective medium parameters include an effective permittivity that is substantially non-constant over a broadband frequency range, an effective permeability that is substantially non-constant over the broadband frequency range, and an effective wave impedance that is substantially constant over the broadband frequency range.

32. An electromagnetic apparatus, comprising:

a plurality of elements having respective characteristic resonance frequencies;

where the elements are spatially distributed to provide at least one effective medium parameter that is substantially constant over a broadband frequency range substantially different from the respective characteristic resonance frequencies, the at least one effective medium parameter being substantially determined by the respective characteristic resonance frequencies.

33. The electromagnetic apparatus of claim 32, where the respective characteristic resonance frequencies correspond to respective electric resonances.

34. The electromagnetic apparatus of claim 32, wherein the broadband frequency range is substantially less than the respective characteristic resonance frequencies.

35. The electromagnetic apparatus of claim 34, wherein a lower limit of the broadband frequency range is substantially zero.

36. The electromagnetic apparatus of claim 34, where the elements have respective resonance bandwidths corresponding to the respective characteristic resonance frequencies, and an upper limit of the broadband frequency range corresponds to a smallest lower limit of the respective resonance bandwidths.

37. The electromagnetic apparatus of claim 32, wherein the broadband frequency range is substantially greater than the respective characteristic resonance frequencies.

38. The electromagnetic apparatus of claim 37, wherein:

the respective characteristic resonance frequencies are respective first characteristic resonance frequencies;

the elements have respective second characteristic resonance frequencies greater than the broadband frequency range; and

the at least one effective medium parameter is substantially determined by the respective first characteristic resonance frequencies and the respective second characteristic resonance frequencies.

39. The electromagnetic apparatus of claim 38, wherein:

the elements have respective first resonance bandwidths corresponding to the respective first characteristic resonance frequencies;

the elements have respective second resonance bandwidths corresponding to the respective second characteristic resonance frequencies;

a lower limit of the broadband frequency range corresponds to a largest upper limit of the respective first resonance bandwidths; and

an upper limit of the broadband frequency range corresponds to a smallest lower limit of the respective second resonance bandwidths.

40. The electromagnetic apparatus of claim 32, wherein some of the respective characteristic resonance frequencies are substantially less than the broadband frequency range, and others of the respective characteristic resonance frequencies are substantially greater than the broadband frequency range.

41. The electromagnetic apparatus of claim 32, wherein the at least one effective medium parameter is an effective permittivity.

42. The electromagnetic apparatus of claim 32, wherein the at least one effective medium parameter is an effective permeability.

43. The electromagnetic apparatus of claim 32, wherein the at least one effective medium parameter is an effective refractive index.

44. The electromagnetic apparatus of claim 32, wherein the at least one effective medium parameter is an effective wave impedance.

45. The electromagnetic apparatus of claim 32, wherein the elements are spatially distributed to further provide at least another effective medium parameters that is substantially non-constant over the broadband frequency range, the at least another effective medium parameter being substantially determined by the respective characteristic resonance frequencies.

46. The electromagnetic apparatus of claim 45, wherein the at least one effective medium parameter is an effective refractive index, and the at least another effective medium parameter is an effective permittivity.

47. The electromagnetic apparatus of claim 45, wherein the at least one effective medium parameter is an effective wave impedance, and the at least another effective medium parameter is an effective permittivity.

48. An electromagnetic apparatus, comprising:

an artificially-structured material that includes a spatial distribution of a plurality of non-resonant elements having respective individual electromagnetic responses, the plurality of respective electromagnetic responses providing a spatially-varying effective refractive index, where the spatially-varying effective refractive index is substantially nondispersive over a broadband frequency range.

49. The electromagnetic apparatus of claim 48, wherein the artificially-structured material defines an input surface region for receiving input electromagnetic energy in the broadband frequency range.

50. The electromagnetic apparatus of claim 49, wherein the input surface region is substantially nonreflective of input electromagnetic energy.

51. The electromagnetic apparatus of claim 50, wherein the spatially-varying effective refractive index gradiently approaches unity at the input surface region.

52. The electromagnetic apparatus of claim 49, wherein the artificially-structured defines an output surface region for transmitting output electromagnetic energy in the broadband frequency range.

53. The electromagnetic apparatus of claim 52, wherein the output surface region is substantially nonreflective of output electromagnetic energy.

54. The electromagnetic apparatus of claim 53, wherein the spatially-varying effective refractive index gradiently approaches unity at the output surface region.

55. The electromagnetic apparatus of claim 49, wherein the plurality of non-resonant elements is responsive to a substantially collimated beam of input electromagnetic energy defining an input beam direction to provide a substantially collimated beam of output electromagnetic energy defining an output beam direction substantially different than the input beam direction.

56. The electromagnetic apparatus of claim 55, wherein the artificially-structured material defines an axial direction directed from the first surface region to the second surface region, and the spatially-varying effective refractive index includes, intermediate the first and second surfaces, a substantially linear gradient along a direction perpendicular to the axial direction.

57. The electromagnetic apparatus of claim 49, wherein the plurality of non-resonant elements is responsive to a substantially collimated beam of input electromagnetic energy to provide a substantially converging beam of output electromagnetic energy.

58. The electromagnetic apparatus of claim 57, wherein the artificially-structured material defines an axial direction directed from the first surface region to the second surface region, and the spatially-varying effective refractive index includes, intermediate the first and second surfaces, a substantially concave variation along a direction perpendicular to the axial direction.

59. The electromagnetic apparatus of claim 49, wherein the plurality of non-resonant elements is responsive to a substantially collimated beam of input electromagnetic energy to provide a substantially diverging beam of output electromagnetic energy.

60. The electromagnetic apparatus of claim 59, wherein the artificially-structured material defines an axial direction directed from the first surface region to the second surface region, and the spatially-varying effective refractive index includes, intermediate the first and second surfaces, a substantially convex variation along a direction perpendicular to the axial direction.

61. An broadband electromagnetic apparatus, comprising:

an artificially-structured material that includes a plurality of adjustable nonresonant elements having respective adjustable individual responses, the plurality of respective adjustable individual responses providing one or more adjustable effective medium parameters.

62. The electromagnetic apparatus of claim 61, wherein the one or more adjustable effective medium parameters includes an adjustable effective permittivity.

63. The electromagnetic apparatus of claim 61, wherein the one or more adjustable effective medium parameters includes an adjustable effective refractive index.

64. The electromagnetic apparatus of claim 61, wherein the adjustable nonresonant elements are adjustable in response to one or more external inputs.

65. The electromagnetic apparatus of claim 61, wherein the one or more external inputs include one or more voltage inputs.

66. The electromagnetic apparatus of claim 61, wherein the one or more external inputs include one or more current inputs.

67. The electromagnetic apparatus of claim 61, wherein the one or more external inputs include one or more optical inputs.

68. The electromagnetic apparatus of claim 61, wherein the one or more adjustable effective medium parameters are substantially non-dispersive over a broadband frequency range.

69. The electromagnetic apparatus of claim 68, wherein the adjustable nonresonant elements are characterized by respective adjustable electric resonance frequencies that substantially exceed the broadband frequency range.

70. The electromagnetic apparatus of claim 61, wherein the adjustable effective medium parameters are substantially determined by respective adjustable physical parameters of the adjustable nonresonant elements.

71. The electromagnetic apparatus of claim 70, wherein the adjustable nonresonant elements include conducting elements having capacitive gaps, and the respective adjustable physical parameters include adjustable capacitances of the capacitive gaps.

72. The electromagnetic apparatus of claim 70, wherein the adjustable nonresonant elements include inductive-capacitive elements having inductive-capacitive resonance frequencies that substantially exceed the broadband frequency range, and the respective adjustable physical parameters include adjustable impedances of the inductive-capacitive elements.

73. The electromagnetic apparatus of claim 72, wherein the adjustable impedances include adjustable capacitances.

74. The electromagnetic apparatus of claim 72, wherein the adjustable impedances include adjustable inductances.

75. The electromagnetic apparatus of claim 72, wherein the adjustable impedances include adjustable resistances.

76. A method, comprising:

selecting a pattern of electromagnetic medium parameters;

determining respective physical parameters for a plurality of nonresonant elements positionable in a spatial arrangement to provide a pattern of effective electromagnetic medium parameters that substantially corresponds to the selected pattern of electromagnetic medium parameters for a broadband frequency range.

77. The method of claim 76, further comprising:

disposing the plurality of nonresonant elements in the spatial arrangement.

78. The method of claim 77, wherein the disposing includes:

fabricating the nonresonant elements; and

assembling the fabricated nonresonant elements in the spatial arrangement.

79. The method of claim 76, wherein the nonresonant elements include I-shaped conducting elements, and the respective physical parameters include geometrical parameters of the I-shaped conducting elements.

80. The method of claim 76, wherein the nonresonant elements include closed-ring conducting elements and the varied respective physical parameters include geometrical parameters of the closed-ring conducting elements.

81. The method of claim 76, wherein the nonresonant elements include conducting elements defining capacitive gaps and the varied respective physical parameters include capacitances of the capacitive gaps.

82. The method of claim 76, wherein the nonresonant elements include inductive-capacitive elements having inductive-capacitive resonance frequencies that substantially exceed the broadband frequency range, and the varied respective physical parameters include impedances of the inductive-capacitive elements.

83. The method of claim 76, wherein the effective electromagnetic medium parameters include a first effective electromagnetic medium parameter that is substantially constant over the broadband frequency range.

84. The method of claim 83, wherein the first effective electromagnetic medium parameter is an effective permittivity.

85. The method of claim 83, wherein the first effective electromagnetic medium parameter is an effective permeability.

86. The method of claim 83, wherein the first effective electromagnetic medium parameter is an effective refractive index.

87. The method of claim 83, wherein the first effective electromagnetic medium parameter is an effective wave impedance.

88. The method of claim 83, wherein the effective electromagnetic medium parameters include a second effective electromagnetic medium parameter that is substantially non-constant over the broadband frequency range.

89. The method of claim 88, wherein the first effective electromagnetic medium parameter is an effective refractive index and the second effective electromagnetic medium parameter is an effective permittivity.

90. The method of claim 88, wherein the first effective electromagnetic medium parameter is an effective wave impedance and the second effective electromagnetic medium parameter is an effective permittivity.

91. The method of claim 76, wherein the nonresonant elements have respective characteristic resonance frequencies that are functions of the respective physical parameters, and the broadband frequency range is substantially different from the respective characteristic resonance frequencies.

92. The method of claim 91, wherein the nonresonant elements have respective resonance bandwidths corresponding to the respective characteristic resonance frequencies, and the broadband frequency range does not overlap with the respective resonance bandwidths.

93. A method, comprising:

selecting an electromagnetic function; and

determining respective physical parameters for a plurality of nonresonant elements positionable in a spatial arrangement to provide the electromagnetic function as an effective medium response of the nonresonant elements over a broadband frequency range.

94. The method of claim 93, wherein the electromagnetic function is a beam-steering function.

95. The method of claim 94, wherein the beam-steering function defines a beam deflection angle, and the selecting of the beam-steering function includes a selecting of the beam deflection angle.

96. The method of claim 93, wherein the electromagnetic function is a beam-focusing function.

97. The method of claim 96, wherein the beam-focusing function defines a focal length, and the selecting of the beam-focusing function includes a selecting of the focal length.

98. The method of claim 97, wherein the selecting of the focal length is a selecting of a negative focal length.

99. The method of claim 97, wherein the selecting of the focal length is a selecting of a positive focal length.

100. The method of claim 93, wherein the electromagnetic function is a cloaking function.

101. The method of claim 100, wherein the cloaking function defines an apparent surface of reflection different than an actual surface of reflection, and the selecting of the cloaking function includes selecting the apparent surface of reflection.

102. The method of claim 101, wherein the actual surface of reflection is a substantially nonplanar surface and the apparent surface of reflection is a substantially planar surface.

103. The method of claim 93, wherein the determining respective physical parameters includes determining according to one of a regression analysis and a lookup table.

104. A method, comprising:

selecting an electromagnetic function;

identifying a pattern of electromagnetic medium parameters suitable to provide the electromagnetic function; and

determining respective physical parameters for a plurality of nonresonant elements positionable in a spatial arrangement to provide a pattern of effective electromagnetic medium parameters that substantially corresponds to the selected pattern of electromagnetic medium parameters for a broadband frequency range.

105. The method of claim 104, wherein the selecting of the electromagnetic function includes selecting or computing a coordinate transformation that substantially defines the electromagnetic function.

106. The method of claim 105, wherein the coordinate transformation is a quasi-conformal coordinate transformation.

107. The method of claim 105, wherein the identifying of the pattern of electromagnetic medium parameters includes applying a transformation optical relation between the electromagnetic medium parameters and the coordinate transformation.

108. The method of claim 104, wherein the determining respective physical parameters includes determining according to one of a regression analysis and a lookup table.

109. A method, comprising:

selecting a pattern of electromagnetic medium parameters for a broadband frequency range; and

for a plurality of adjustable nonresonant elements having respective adjustable physical parameters and positioned in a spatial arrangement, determining respective values of the respective adjustable physical parameters to provide a pattern of effective electromagnetic medium parameters that substantially corresponds to the selected pattern of electromagnetic medium parameters.

110. The method of claim 109, wherein the respective adjustable physical parameters are determined by one or more control inputs, and the method includes:

providing the one or more control inputs corresponding to the determined respective values of the respective adjustable physical parameters.

111. The method of claim 110, wherein the one or more control inputs includes one or more voltage inputs.

112. The method of claim 110, wherein the one or more control inputs includes one or more thermal inputs.

113. The method of claim 110, wherein the one or more control inputs includes one or more optical inputs.

114. The method of claim 109, wherein the adjustable nonresonant elements include conducting elements having capacitive gaps, and the respective adjustable physical parameters include adjustable capacitances of the capacitive gaps.

115. The method of claim 109, wherein the adjustable nonresonant elements include inductive-capacitive elements having inductive-capacitive resonance frequencies that substantially exceed the broadband frequency range, and the respective adjustable physical parameters include adjustable impedances of the inductive-capacitive elements.

116. A method, comprising:

selecting an electromagnetic function; and

for a plurality of adjustable nonresonant elements having respective adjustable physical parameters and positioned in a spatial arrangement, determining respective values of the respective adjustable physical parameters to provide the electromagnetic function as an effective medium response of the nonresonant elements over a broadband frequency range.

117. A method, comprising:

selecting an electromagnetic function;

identifying a pattern of electromagnetic medium parameters suitable to provide the electromagnetic function; and

for a plurality of adjustable nonresonant elements having respective adjustable physical parameters and positioned in a spatial arrangement, determining respective values of the respective adjustable physical parameters to provide a pattern of effective electromagnetic medium parameters that substantially corresponds to the selected pattern of electromagnetic medium parameters.