Photonic crystals and devices having tunability and switchability

• US 6,859,304 B2
• Filed: 08/09/2002
• Issued: 02/22/2005
• Est. Priority Date: 08/09/2002
• Status: Expired due to Fees

• Current Assignee: Energy Conversion Devices
• Original Assignee: Energy Conversion Devices
• Inventors: Miller, Robert O., Tsu, David
• Primary Examiner(s): Ben, Loha
• Application Number:
  US10/216,404
• Publication Number:
  US 20040027646A1
• Time in Patent Office: 928 Days
• Field of Search: 359/322, 359/237, 359/245, 359/238, 359/278, 359/279, 359/321, 359/326, 359/332, 359/350, 359/361, 343/772, 343/786, 343/787, 343/895, 343/909, 365/113, 365/163, 369/275.2, 250/214.1, 257/2, 257/4
• US Class Current: 359/322
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: G02B 6/12007 forming wavelength selective elements, e.g. multiplexer, demultiplexer
• CPC Class Codes: G02B 6/1225 comprising photonic band-gap structures or photonic lattices
• CPC Class Codes: G02F 1/0054 Structure, phase transitions, NMR, ESR, Moessbauer spectra
• CPC Class Codes: G02F 1/011 in optical waveguides, not otherwise provided for in this subclass
• CPC Class Codes: G02F 1/0147 based on thermo-optic effects G02F1/132 takes precedence
• CPC Class Codes: G02F 2202/32 Photonic crystals
• CPC Class Codes: H01P 1/2005 Electromagnetic photonic bandgaps [EPB], or photonic bandgaps [PBG]

Abstract

A photonic crystal having reversibly tunable photonic properties. The photonic crystal includes a phase change material having a plurality of structural states that vary with respect to fractional crystallinity. Optical constants including refractive index, extinction coefficient and permittivity vary as the fractional crystallinity of the phase change material is varied thereby providing tunability of photonic crystal properties. Variations among the structural states of the phase change material are reversibly effected through the addition of energy in forms including optical or electrical energy. The photonic crystals may include defects that provide photonic states within the photonic band gap. The position of these states is tunable through the control of the fractional crystallinity of the phase change material included in the photonic crystal. Electromagnetic radiation resonators including photonic crystals having photonic states in the photonic band gap are further provided. These resonators may be used for frequency selective filtering or routing of electromagnetic radiation and permit tunable variation in the frequency and decay rates of resonant modes through control of the structural state of the phase change material. These resonators are further coupled to waveguides to provide tunable channel drop filters and narrowband reflectors.

Claims

1. A photonic crystal including units of a macroscopic dielectric medium periodically arranged within a surrounding dielectric medium, said photonic crystal comprising a phase change material, said phase change material having a plurality of structural states, said structural states including an amorphous state and a crystalline state, said phase change material being reversibly transformable among said structural states upon the providing of energy.

2. The photonic crystal of claim 1, wherein said units of macroscopic dielectric medium comprise said phase change material.

3. The photonic crystal of claim 1, wherein at least two of said plurality of structural states are present in said photonic crystal.

4. The photonic crystal of claim 1, wherein the refractive index of said amorphous state and said crystalline state differ by at least 10% at one or more frequencies within the photonic band gap of said photonic crystal.

5. The photonic crystal of claim 1, wherein the refractive index of said amorphous state and said crystalline state differ by at least 25% at one or more frequencies within the photonic band gap of said photonic crystal.

6. The photonic crystal of claim 1, wherein the refractive index of said amorphous state and said crystalline state differ by at least 50% at one or more frequencies within the photonic band gap of said photonic crystal.

7. The photonic crystal of claim 1, wherein the extinction coefficient of said amorphous state and said crystalline state differ by at least 20% at one or more frequencies within the photonic band gap of said photonic crystal.

8. The photonic crystal of claim 1, wherein the extinction coefficient of said amorphous state and said crystalline state differ by at least 50% at one or more frequencies within the photonic band gap of said photonic crystal.

9. The photonic crystal of claim 1, wherein the extinction coefficient of said amorphous state and said crystalline state differ by at least 75% at one or more frequencies within the photonic band gap of said photonic crystal.

10. The photonic crystal of claim 1, wherein the ratio of the refractive index to the extinction coefficient of said amorphous state and said crystalline state differ by at least 10% at one or more frequencies within the photonic band gap of said photonic crystal.

11. The photonic crystal of claim 1, wherein the ratio of the refractive index to the extinction coefficient of said amorphous state and said crystalline state differ by at least 25% at one or more frequencies within the photonic band gap of said photonic crystal.

12. The photonic crystal of claim 1, wherein the ratio of the refractive index to the extinction coefficient of said amorphous state and said crystalline state differ by at least 50% at one or more frequencies within the photonic band gap of said photonic crystal.

13. The photonic crystal of claim 1, wherein said plurality of structural states further includes one or more partially crystalline states, said partially crystalline states including amorphous phase regions and crystalline phase regions.

14. The photonic crystal of claim 1, wherein said phase change material comprises an element selected from the group consisting of In, Ag, Te, Se, Ge, Sb, Bi, Pb, Sn, As, S, Si, P, O and mixtures and alloys thereof.

15. The photonic crystal of claim 14, wherein said phase change material further comprises a transition metal element.

16. The photonic crystal of claim 1, wherein said phase change material comprises a chalcogen.

17. The photonic crystal of claim 16, wherein said chalcogen is Te.

18. The photonic crystal of claim 17, wherein said phase change material further comprises Ge, Sb or Cd.

19. The photonic crystal of claim 1, wherein said phase change material has a eutectic composition.

20. The photonic crystal of claim 1, wherein said phase change material comprises Ag and In.

21. The photonic crystal of claim 20, wherein said phase change material further comprises Sb or Te.

22. The photonic crystal of claim 1, wherein said photonic crystal further comprises SiO₂.

23. The photonic crystal of claim 22, wherein said surrounding dielectric medium comprises SiO₂.

24. The photonic crystal of claim 1, wherein said units of macroscopic dielectric medium are comprised of air.

25. The photonic crystal of claim 1, wherein said energy is provided in the form of optical energy.

26. The photonic crystal of claim 1, wherein said energy is provided in the form of electrical energy.

27. The photonic crystal of claim 1, wherein said units of macroscopic dielectric medium are substantially uniform with respect to size, shape, and optical constants.

28. The photonic crystal of claim 27, wherein one or more of said uniform units is modified to form one or more defect units, wherein said defect units differ in size, shape, or optical constants from said uniform units.

29. The photonic crystal of claim 28, wherein said one or more defect units provides one or more photonic states in the photonic band gap of said photonic crystal.

30. A photonic device comprising:

a bus waveguide;

a resonator comprising the photonic crystal of claim 29, said resonator having one or more resonant modes, said resonant modes having resonant frequencies, said resonant frequencies being determined by said one or more defect photonic states; and

a drop waveguide parallel to said bus waveguide;

wherein said resonator is coupled to said bus waveguide and said drop waveguide.

31. The photonic device of claim 30, wherein said resonator is symmetrically disposed about a plane normal to the bus waveguide.

32. The photonic device of claim 30, wherein said bus waveguide and said drop waveguide are comprised of a photonic crystal.

33. The photonic device of claim 30, wherein said resonant frequencies are microwave, infrared, or visible frequencies.

34. The photonic device of claim 30, wherein an input data stream is provided to said bus waveguide, said input stream including one or more input frequencies of electromagnetic radiation, said one or more input frequencies including an input resonant frequency, said input resonant frequency corresponding to one of said resonant frequencies of said resonator, said input resonant frequency being transferred from said bus waveguide to said drop waveguide by said resonator.

35. The photonic device of claim 34, wherein said transfer occurs without reflection or transmission of said input resonant frequency from said resonator to said bus waveguide.

36. The photonic device of claim 34, wherein said transfer occurs substantially in the forward drop direction.

37. The photonic device of claim 34, further comprising means for providing energy to said phase change material, said means for providing energy providing energy in an amount sufficient to change the structural state of said phase change material.

38. The photonic device of claim 37, wherein said change in structural state changes the frequency of one or more of said resonant frequencies.

39. The photonic device of claim 37, wherein said change in structural state modulates said transfer.

40. The photonic device of claim 37, wherein said change in structural state switches said transfer.

41. The photonic crystal of claim 29, wherein said defect photonic state has a resonant frequency in the infrared.

42. The photonic crystal of claim 1, wherein said photonic crystal is two-dimensional.

43. The photonic crystal of claim 42, wherein said units of macroscopic dielectric medium are rods.

44. The photonic crystal of claim 43, wherein said rods are periodically arranged in a square lattice.

45. The photonic crystal of claim 43, wherein said rods are periodically arranged in a triangular lattice.

46. The photonic crystal of claim 43, wherein said rods have a non-circular cross-section.

47. The photonic crystal of claim 43, wherein said rods comprise said phase change material.

48. The photonic crystal of claim 47, wherein said phase change material forms a capping layer, an internal layer or a coating layer of said rod.

49. The photonic crystal of claim 47, wherein said rod further comprises a metallic layer or a protective layer.

50. An electromagnetic radiation frequency reflector comprising the photonic crystal of claim 1, said photonic crystal having a photonic band gap having a low frequency edge and a high frequency edge, said reflector reflecting incident light having a frequency in between said low frequency edge and said high frequency edge.

51. A method of tuning a photonic crystal, said method including the steps of:

providing the photonic crystal of claim 1,

providing energy to said photonic crystal, said energy producing a change in the structural state of said phase change material.