EFFICIENT TERAHERTZ SOURCES BY OPTICAL RECTIFICATION IN PHOTONIC CRYSTALS AND METAMATERIALS EXPLOITING TAILORED TRANSVERSE DISPERSION RELATIONS

• US 20070297734A1
• Filed: 06/19/2007
• Published: 12/27/2007
• Est. Priority Date: 06/23/2006
• Status: Active Grant

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Ibanescu, Mihai, Reed, Evan, Rakich, Peter, Ippen, Erich, Soljacic, Marin, Hamam, Rafif, Joannopoulos, John, Johnson, Steven
• Granted Patent: US 7,421,171 B2
• Time in Patent Office: Days
• US Class Current: 385/125
• CPC Class Codes: G02F 1/3534 Three-wave interaction, e.g. sum-difference frequency generation G02F1/3532 takes precedence
• CPC Class Codes: G02F 2202/32 Photonic crystals
• CPC Class Codes: G02F 2203/13 involving THZ radiation

Abstract

A system and a method for generating terahertz (THz) radiation are provided. The system includes a photonic crystal structure comprising at least one nonlinear material that enables optical rectification. The photonic crystal structure is configured to have the suitable transverse dispersion relations and enhanced density photonic states so as to allow THz radiation to be emitted efficiently when an optical or near infrared pulse travels through the nonlinear part of the photonic crystal.

Claims

1. A system for generating terahertz (THz) radiation comprising a photonic crystal structure including at least one nonlinear material that enables optical rectification, said photonic crystal structure being configured to have the suitable transverse dispersion relations and enhanced density photonic states so as to allow THz radiation to be emitted efficiently when an optical or near infrared pulse travels through the nonlinear part of said photonic crystal structure.

2. The system of claim 1, wherein said photonic crystal is configured to have a frequency range (Δ

ω

) equal to 0.1% around some ω

_Thz, such that the number of photonic states in the Δ

ω

is >

10 times larger than the number of photonic states the same frequency range would contain in the same, but unpatterned nonlinear material.

3. The system of claim 1, wherein said photonic crystal is configured to have a frequency range (Δ

ω

) equal to 0.1% around some ω

_Thz, such that the number of photonic states in the Δ

ω

is >

1000 times larger than the number of photonic states the same frequency range would contain in the same, but unpatterned nonlinear material.

4. The system of claim 1, wherein said photonic crystal is configured to have a frequency range (Δ

ω

) equal to 2% around some ω

_Thz, such that the number of photonic states in the Δ

ω

is >

10 times larger than the number of photonic states the same frequency range would contain in the same, but unpatterned nonlinear material.

5. The system of claim 1, wherein said photonic crystal is configured to have a frequency range (Δ

ω

) equal to 2% around some ω

_Thz, such that the number of photonic states in the Δ

ω

is >

1000 times larger than the number of photonic states the same frequency range would contain in the same, but unpatterned nonlinear material.

6. The system of any of the claims 2-5, wherein said incident optical or near infrared pulse travels through the nonlinear part of said photonic crystal, with a group velocity v such that the Cherenkov condition between ω

_Thz and the longitudinal k-vector of the Terahertz radiation k_Thz is satisfied at the narrow frequency range Δ

ω

, namely;

ω

_Thz=v*(k_Thz+G), where G is any reciprocal wavevector of the said photonic crystal.

7. The system of claim 6, wherein said photonic crystal comprises a 2D square lattice of dielectric rods.

8. The system of claim 6, wherein said photonic crystal comprises a 2D periodic photonic crystal structure.

9. The system of claim 6, wherein said photonic crystal comprises a 3D periodic photonic crystal structure.

10. The system of claim 6, wherein said photonic crystal comprises a 2D periodic photonic crystal slab.

11. The system of claim 6, wherein said photonic crystal comprises line defects.

12. The system of claim 6, wherein said photonic crystal comprises a planar array of coupled cavities to break symmetry of the photonic crystal in the transverse direction.

13. The system of claim 6, wherein said photonic crystal comprises longitudinal variations of the parameters of the photonic crystal.

14. The system of claim 6, wherein said photonic crystal comprises a linear waveguide to guide the incident or near infrared pulse.

15. A method of producing terahertz (THz) radiation comprising:

providing an optical or near infrared pulse;

providing a photonic crystal structure comprising at least one nonlinear material that enables optical rectification; and

configuring said photonic crystal structure to have the suitable transverse dispersion relations and enhanced density photonic states so as to allow THz radiation to be emitted efficiently when said optical or near infrared pulse travels through the nonlinear part of the said photonic crystal structure.

16. The method of claim 15, wherein said photonic crystal is configured to have a frequency range (Δ

ω

) equal to 0.1% around some ω

_Thz, such that the number of photonic states in the Δ

ω

is >

10 times larger than the number of photonic states the same frequency range would contain in the same, but unpatterned nonlinear materials.

17. The method of claim 15, wherein said photonic crystal is configured to have a frequency range (Δ

ω

) equal to 0.1% around some ω

_Thz, such that the number of photonic states in the Δ

ω

is >

1000 times larger than the number of photonic states the same frequency range would contain in the same, but unpatterned nonlinear materials.

18. The method of claim 15, wherein said photonic crystal is configured to have a frequency range (Δ

ω

) equal to 2% around some ω

_Thz, such that the number of photonic states in the Δ

ω

is >

10 times larger than the number of photonic states the same frequency range would contain in the same, but unpatterned nonlinear materials.

19. The method of claim 15, wherein said photonic crystal is configured to have a frequency range (Δ

ω

) equal to 2% around some ω

_Thz, such that the number of photonic states in the Δ

ω

is >

1000 times larger than the number of photonic states the same frequency range would contain in the same, but unpatterned nonlinear materials.

20. The method of any of the claims 16-19, wherein said incident optical or near infrared pulse travels through the nonlinear part of said photonic crystal, with a group velocity v such that the Cherenkov condition between ω

_Thz and the longitudinal k-vector of the Terahertz radiation k_Thz is satisfied at the narrow frequency range Δ

ω

, namely;

ω

_Thz=v*(k_Thz+G), where G is any reciprocal wavevector of the said photonic crystal.

21. The method of claim 20, wherein said photonic crystal comprises a 2D square lattice of dielectric rods.

22. The method of claim 20, wherein said photonic crystal comprises a 2D periodic photonic crystal structure.

23. The method of claim 20, wherein said photonic crystal comprises a 3D periodic photonic crystal structure.

24. The method of claim 20, wherein said photonic crystal comprises a 2D periodic photonic crystal slab.

25. The method of claim 20, wherein said photonic crystal comprises line defects.

26. The method of claim 20, wherein said photonic crystal comprises a planar array of coupled cavities to break symmetry of the photonic crystal in the transverse direction.

27. The method of claim 20, wherein said photonic crystal comprises longitudinal variations of the parameters of the photonic crystal.

28. The method of claim 20, wherein said photonic crystal comprises a linear waveguide to guide the incident or near infrared pulse.

29. A method of forming a terahertz (THz) radiation source comprising:

forming a photonic crystal structure including at least one nonlinear material that enables optical rectification; and

configuring said photonic crystal structure to have the suitable transverse dispersion relations and enhanced density photonic states so as to allow THz radiation to be emitted efficiently when an optical or near infrared pulse travels through the nonlinear part of the said photonic crystal structure.

30. The system of claim 29, wherein said photonic crystal is configured to have a frequency range (Δ

ω

) equal to 0.1% around some ω

_Thz, such that the number of photonic states in the Δ

ω

is >

10 times larger than the number of photonic states the same frequency range would contain in the same, but unpatterned nonlinear materials.

31. The system of claim 29, wherein said photonic crystal is configured to have a frequency range (Δ

ω

) equal to 0.1% around some ω

_Thz, such that the number of photonic states in the Δ

ω

is >

1000 times larger than the number of photonic states the same frequency range would contain in the same, but unpatterned nonlinear materials.

32. The system of claim 29, wherein said photonic crystal is configured to have a frequency range (Δ

ω

) equal to 2% around some ω

_Thz, such that the number of photonic states in the Δ

ω

is >

10 times larger than the number of photonic states the same frequency range would contain in the same, but unpatterned nonlinear materials.

33. The system of claim 29, wherein said photonic crystal is configured to have a frequency range (Δ

ω

) equal to 2% around some ω

_Thz, such that the number of photonic states in the Δ

ω

is >

1000 times larger than the number of photonic states the same frequency range would contain in the same, but unpatterned nonlinear materials.

34. The system of any of the claims 30-33, wherein said incident optical or near infrared pulse travels through the nonlinear part of said photonic crystal, with a group velocity v such that the Cherenkov condition between ω

_Thz and the longitudinal k-vector of the Terahertz radiation k_Thz is satisfied at the narrow frequency range Δ

ω

, namely;

ω

_Thz=v*(k_Thz+G), where G is any reciprocal wavevector of the said photonic crystal.

35. The system of claim 34, wherein said photonic crystal comprises a 2D square lattice of dielectric rods.

36. The system of claim 34, wherein said photonic crystal comprises a 2D periodic photonic crystal structure.

37. The system of claim 34, wherein said photonic crystal comprises a 3D periodic photonic crystal structure.

38. The system of claim 34, wherein said photonic crystal comprises a 2D periodic photonic crystal slab.

39. The system of claim 34, wherein said photonic crystal comprises line defects.

40. The system of claim 34, wherein said photonic crystal comprises a planar array of coupled cavities to break symmetry of the photonic crystal in the transverse direction.

41. The system of claim 34, wherein said photonic crystal comprises longitudinal variations of the parameters of the photonic crystal.

42. The system of claim 34, wherein said photonic crystal comprises a linear waveguide to guide the incident or near infrared pulse.