Holographic polymer photonic crystal

• US 20030214690A1
• Filed: 11/26/2002
• Published: 11/20/2003
• Est. Priority Date: 11/26/2001
• Status: Abandoned Application

• Current Assignee: Brown University
• Original Assignee: Brown University
• Inventors: Escuti, Michael J., Crawford, Gregory P.
• Application Number:
  US10/304,578
• Publication Number:
  US 20030214690A1
• Time in Patent Office: Days
• US Class Current: 359/15
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: G02B 5/32 Holograms used as optical elements
• CPC Class Codes: G02B 6/1225 comprising photonic band-gap structures or photonic lattices
• CPC Class Codes: G02F 1/13342 Holographic polymer dispersed liquid crystals
• CPC Class Codes: G02F 2202/32 Photonic crystals

Abstract

A photonic crystal having a polymer matrix of a first index of refraction and a second material arranged in a crystal lattice and having a second index of refraction is presented. The second material may be an active material such as a liquid crystal and the active material may have an optical property that can be modulated by an external field. Methods for making such crystals using holographic polymerization of a photosensitive monomer in a composition including the monomer and a non-photosensitive material are described. In some aspects, the photosensitive monomer and the non-photosensitive material, e.g., a liquid crystal, may be phase-separated upon exposure to a pre-calculated interference pattern of light such as is obtained by the superposition of a number of coherent light beams. Various applications are described, such as in optical communication switching, filtering, display devices and other commercial and scientific applications.

Claims

1. A method for modulating a light source, comprising:

providing a composition including a photosensitive monomer and an active material;

forming an interference pattern of light from at least three substantially-additive coherent light beams;

applying the interference pattern of light to the composition;

polymerizing the photosensitive monomer, thereby phase-separating the composition into a polymer matrix and a plurality of active material domains, said active material domains arranged in a two- or three-dimensional lattice; and

applying an external field to the active material to modify an optical characteristic of the active material and modulate the light source.

2. The method of claim 1, wherein the active material comprises a liquid crystal.

3. The method of claim 1, wherein the active material domains comprise topologically-unconnected regions substantially occupied by the active material.

4. The method of claim 3, wherein the active material domains comprise topologically-unconnected regions are closed.

5. The method of claim 4, wherein the topologically-unconnected closed regions are contained within the polymer matrix.

6. The method of claim 1, wherein the polymer matrix comprises domains of topologically-unconnected regions substantially occupied by the polymer.

7. The method of claim 1, wherein the topologically-unconnected regions are closed.

8. The method of claim 1, further comprising calculating an intensity field of the interference pattern of light using an algorithm.

9. The method of claim 8, wherein the algorithm comprises a series of mathematical steps corresponding to a set of governing equations.

10. The method of claim 1, further comprising modulating an amplitude of the external field between a first amplitude and a second amplitude.

11. The method of claim 10, wherein the optical characteristic has a first value at the first amplitude and a second value at the second amplitude.

12. The method of claim 10, wherein the first amplitude is substantially zero.

13. The method of claim 1, wherein the external field is an electromagnetic field.

14. The method of claim 1, wherein the external field comprises a modulated alternating current (AC) signal.

15. The method of claim 1, wherein the optical characteristic is an index of refraction.

16. The method of claim 1, further comprising calculating a set of lattice constants defined by the interference pattern of light.

17. The method of claim 1, wherein the interference pattern corresponds to a plurality of superposed lattice patterns.

18. The method of claim 1, wherein the interference pattern corresponds to a Bravais lattice.

19. The method of claim 18, wherein the Bravais lattice comprises a hexagonal close packed (HCP) lattice.

20. The method of claim 18, wherein the Bravais lattice comprises a face-centered cubic lattice (FCC).

21. The method of claim 1, further comprising applying a defect-generating pattern of light to the composition to generate defects within the lattice.

22. An optical device, comprising:

a substantially-solid three-dimensional polymer matrix; and

an active material disposed in and substantially filling a plurality topologically-unconnected, closed domains within the polymer matrix, said domains defining locations of a three-dimensional lattice, wherein the active material has an optical characteristic that may be actively controlled using an externally-applied field.

23. The device of claim 22, wherein the optical characteristic is an index of refraction.

24. The device of claim 22, wherein the active material and the polymer matrix have different indices of refraction.

25. The device of claim 22, wherein the externally-applied field is an electromagnetic field.

26. The device of claim 22, wherein the active material comprises any of:

a liquid crystal, a composite and a suspension.

27. The device of claim 22, wherein the device provides a tunable photonic band gap that selectively substantially blocks propagation of light within a frequency range defined by the band gap.

28. The device of claim 22, wherein the device provides a tunable polarizer.

29. The device of claim 28, wherein the tunable polarizer operates in a selected frequency band.

30. The device of claim 22, wherein the polymer matrix is formed by polymerizing a photosensitive monomer using a holographically-generated interference pattern of a plurality of coherent light beams.

31. The device of claim 30, further comprising a defect within the active material lattice.

32. The device of claim 22, wherein the topologically-unconnected, closed domains of active material are formed by phase separation of the active material from the polymer matrix.

33. The device of claim 22, wherein the three-dimensional lattice has a pattern that corresponds to a plurality of superposed lattice patterns.

34. The device of claim 22, wherein the lattice comprises a Bravais lattice.

35. The device of claim 34, wherein the Bravais lattice comprises a hexagonal close packed (HCP) lattice.

36. The device of claim 34, wherein the Bravais lattice comprises a face-centered cubic lattice (FCC).

37. A computer system for calculating an interference pattern of light for application to a photosensitive material, the computer system comprising:

a storage device that stores instructions corresponding to a governing set of equations;

an input interface that receives input data corresponding to a desired optical characteristic of the photosensitive material;

a processor operative to receive the input data, execute the stored instructions on the input data to calculate an intensity field for each of a plurality of simulated coherent light beams and sum the calculated intensity fields to yield a simulated two- or three-dimensional interference pattern of light having a plurality of bright or dark regions; and

an output interface that provides an output representative of the simulated two- or three-dimensional interference pattern of light, the output adapted for generation of an actual two- or three-dimensional interference pattern of light that locally modifies an optical characteristic of the photosensitive material corresponding to the bright or dark regions.

38. The computer system of claim 37, wherein the processor is further operative to execute instructions to calculate an external field acting on the photosensitive material, and to generate a corresponding output operative to modulate the optical property of the photosensitive material.

39. The computer system of claim 37, wherein the input data includes data identifying a wave vector and a polarization vector for at least one of the simulated coherent light beams.

40. The computer system of claim 39, wherein the polarization vector is defined with respect to the wave vector.

41. The computer system of claim 37, wherein the stored instructions comprise a photonic band gap solver.

42. The computer system of claim 37, wherein the stored instructions comprise a multi-beam holographic interference solver.

43. The computer system of claim 37, further wherein the output interface is coupled to a beam controller that controls the coherent light beams.

44. The computer system of claim 37, further wherein the processor is further operative to calculate an interference pattern of light corresponding to a superposition of a plurality of lattice patterns.

45. A method for making an active optical component, comprising:

providing a composition including a photosensitive monomer and an active material;

forming an interference pattern of light from at least three substantially-additive coherent light beams;

applying the interference pattern of light to the composition; and

polymerizing the photosensitive monomer, using the interference pattern of light, thereby phase-separating the composition to yield a polymer matrix and a two- or three-dimensional lattice of the active material within the polymer matrix.

46. The method of claim 45, wherein the active material comprises any of:

a liquid crystal, a composite and a suspension.

47. The method of claim 45, wherein the two- or three-dimensional lattice comprises topologically-unconnected domains substantially occupied by the active material.

48. The method of claim 47, wherein the topologically-unconnected regions are closed.

49. The method of claim 45, further comprising modulating an optical characteristic of the active material using an external field applied to the active material.

50. The method of claim 49, wherein the external field is an electromagnetic field.

51. The method of claim 45, wherein the at least three substantially-additive coherent light beams irradiate the photosensitive monomer from a same face of the composition.

52. The method of claim 45, further comprising applying a defect-generating pattern of light to the composition to generate defects within the lattice.

53. The method of claim 45, wherein forming the interference pattern of light comprises forming at least two patterns of light and applying the interference pattern of light comprises applying the at least two patterns of light in separate steps.

54. The method of claim 53, wherein the at least two patterns of light are applied in temporally distinct stages.

55. The method of claim 53, wherein the at least two patterns of light are applied to a corresponding at least two distinct spatial regions.

56. A photonic device fabrication method, comprising:

applying light in a light intensity pattern to a composition including a photosensitive monomer and an active material;

phase-separating the composition by polymerizing the photosensitive monomer into a polymer matrix having a three-dimensional morphology corresponding to the light intensity pattern, including a plurality of active material-filled topologically-unconnected, closed regions contained within the polymer matrix;

wherein said regions define locations of a three-dimensional lattice; and

wherein all regions of the polymer matrix are formed substantially at the same time and globally over the device in its entirety by exposing the device as a whole to the light intensity pattern.

57. The method of claim 56, wherein the active material comprises a liquid crystal.

58. The method of claim 56, further comprising calculating a light intensity pattern using a multi-beam holographic interference solver.

59. The method of claim 56, further comprising calculating a light intensity pattern corresponding to a superposition of a plurality of lattice patterns.

60. A method for making a photonic device, comprising:

applying light in a light intensity pattern to a composition including at least a first material and a second material, said first material having a first index of refraction and said second material having a second index of refraction, wherein said first and second indices of refraction are different and wherein at least said first material is a photosensitive monomer;

phase-separating said composition into a plurality of regions by polymerizing at least said first materials to yield a polymer matrix and a plurality of topologically-unconnected regions disposed within said polymer matrix;

wherein said topologically-unconnected regions comprise a lattice having domains substantially occupied by second material.

61. The method of claim 60, wherein said second material comprises a monomer.

62. The method of claim 60, wherein said second material comprises a polymer.

63. The method of claim 60, wherein said second material comprises a composite.

64. The method of claim 63, wherein said composite comprises a suspension.

65. The method of claim 64, wherein said suspension comprises an active material.

66. An optical device, comprising:

a composition that is phase-separated by application of a light pattern into a first region comprising a substantially-solid three-dimensional polymer matrix comprising a first polymer having a first index of refraction; and

a second region comprising a second polymer, having a second index of refraction, disposed in and substantially filling a plurality topologically-unconnected, closed domains within the polymer matrix, said domains defining locations of a three-dimensional photonic lattice.

67. The device of claim 66, wherein the active material and the polymer matrix have different indices of refraction.

68. The device of claim 66, wherein the device provides a photonic band gap that selectively substantially blocks propagation of light within a frequency range defined by the band gap.

69. The device of claim 66, wherein the polymer matrix is formed by polymerizing a photosensitive monomer using a holographically-generated interference pattern of a plurality of coherent light beams.