Dynamic wavelength shifting method

• US 6,717,717 B2
• Filed: 07/16/2001
• Issued: 04/06/2004
• Est. Priority Date: 07/16/2001
• Status: Active Grant

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Nelson, Keith A.
• Primary Examiner(s): Lee, John D.
• Application Number:
  US09/906,530
• Publication Number:
  US 20030011871A1
• Time in Patent Office: 995 Days
• Field of Search: 359/326-332
• US Class Current: 359/326
• CPC Class Codes: G02F 1/353 Frequency conversion, i.e. wherein a light beam is generated with frequency components different from those of the incident light beams

Abstract

Methods and systems are disclosed that dynamically shift the wavelength of an electromagnetic (EM) beam by interacting the beam with a polariton wave having a selected polariton wave frequency.

Claims

1. A method for shifting the frequency of an electromagnetic beam carrying a telecommunication signal, the method comprising:

generating in a material a polariton wave having a polariton wave frequency; and

directing the beam carrying the telecommunication signal to interact with the polariton wave and cause at least portion of the beam to shift in frequency by an amount corresponding to the polariton wave frequency.

2. The method of claim 1 further comprising selecting the polariton wave frequency based on a desired frequency shift for the electromagnetic beam.

3. The method of claim 1 further comprising adjusting the polariton wave frequency to cause a corresponding adjustment to the frequency shift.

4. The method of claim 3, wherein the adjustment of the polariton wave frequency comprises applying an external electric field to the material.

5. The method of claim 1, further comprising adjusting the frequency shift by repeating the generating and directing steps for a polariton wave having a different polariton wave frequency corresponding to the adjusted frequency shift.

6. The method of claim 1, further comprising allowing the polariton wave to propagate in the material prior to its interaction with the electromagnetic beam.

7. The method of claim 1, further comprising introducing a delay between the generation of the polariton wave and its interaction with the electromagnetic beam.

8. The method of claim 1, wherein the generation of the polariton wave is selected to occur at a first spatial region of the material and the interaction between the polariton wave and the electromagnetic beam is selected to occur at a different, second spatial region of the material.

9. The method of claim 1, wherein the material defines a polariton wave cavity resonant with the polariton wave frequency.

10. The method of claim 9, further comprising selecting the polariton wave frequency by applying an external electric field to the material to adjust the effective cavity length of the resonant cavity.

11. The method of claim 9, further comprising resonantly pumping the cavity to increase the intensity or frequency selectivity of the polariton wave.

12. The method of claim 9, wherein the material defines an array of cavities each having a resonant polariton wave frequency.

13. The method of claim 12, further comprising selecting a desired polariton wave frequency, and wherein the generation of the polariton wave comprises generating the polariton wave in the cavity corresponding to the desired polariton wave frequency.

14. The method of claim 9, wherein the material comprises at least one constituent material having a transverse dimension sufficient to define the resonant cavity.

15. The method of claim 1, wherein the frequency-shift equals the polariton wave frequency or a harmonic of the polariton wave frequency.

16. The method of claim 1, wherein the frequency-shift is selected to be positive.

17. The method of claim 1, wherein the frequency-shift is selected to be negative.

18. The method of claim 1, wherein the electromagnetic beam carries the telecommunication signal as a modulated intensity profile or a modulated phase profile.

19. The method of claim 1, wherein the electromagnetic beam carrying the telecommunication signal has a coherent bandwidth that is less than the frequency shift.

20. The method of claim 1, wherein the electromagnetic beam comprises pulsed electromagnetic radiation.

21. The method of claim 1, wherein the electromagnetic beam comprises continuous-wave (cw) or quasi-cw electromagnetic radiation.

22. The method of claim 1, wherein the electromagnetic beam is directed to the material by an optical waveguide.

23. The method of claim 1, wherein the polariton wave frequency is in the range of about 50 GHz to about 10 THz.

24. The method of claim 1, wherein the electromagnetic beam has a central wavelength in the range of about 300 nm to 2.5 microns.

25. The method of claim 1, wherein the material comprises a crystalline material.

26. The method of claim 25, wherein the material comprises a ferroelectric or a semiconductor crystal.

27. The method of claim 1, wherein the material comprises a non-centrosymmetric material.

28. The method of claim 1, wherein the generation of the polariton wave comprises optically exciting the material.

29. The method of claim 28, wherein the optical excitation of the polariton wave comprises directing at least one pulse of optical radiation to the material, wherein the optical pulse has a pulse duration shorter than the inverse of the polariton wave frequency.

30. The method of claim 29, wherein the pulse duration is shorter than 10 ps.

31. The method of claim 28, wherein the optical excitation of the polariton wave comprises simultaneously directing at least two optical excitation beams to overlap in the material, wherein any two of the optical excitation beams differ in frequency by an amount equal to the polariton wave frequency.

32. The method of claim 28, wherein the optical excitation of the polariton wave comprises forming an optical excitation grating pattern in the material.

33. The method of claim 32, wherein the formation of the optical excitation grating pattern comprises crossing a pair of optical excitation beams on the material.

34. The method of claim 32, wherein the formation of the optical excitation grating pattern comprises directing optical radiation to a mask and imaging at least a portion of the masked light into the material.

35. The method of claim 32, further comprising adjusting the period of the optical excitation grating pattern to select the polariton wave frequency.

36. The method of claim 28, wherein the optical excitation of the polariton wave comprises coupling electromagnetic radiation at the polariton wave frequency into the material.

37. The method of claim 1, wherein the generation of the polariton wave comprises directing at least one electrical pulse to the material, wherein the electrical pulse has a pulse duration shorter than the inverse of the polariton wave frequency.

38. The method of claim 1, wherein the beam is directed into the material supporting the polariton wave to interact with the polariton wave.

39. The method of claim 1, wherein the beam is directed to a region proximate the material supporting the polariton wave to interact with the polariton wave.

40. A method for shifting the frequency of an electromagnetic beam, the method comprising:

selecting a polariton wave frequency based on a desired frequency shift for the electromagnetic beam;

optically exciting a material to generate a polariton wave having the selected polariton wave frequency; and

directing the beam to interact with the polariton wave and cause at least portion of the beam to shift in frequency by an amount corresponding to the polariton wave frequency,

wherein the optical excitation of the polariton wave comprises forming an optical excitation grating pattern in the material.

41. A method for shifting the frequency of an electromagnetic beam, the method comprising:

optically exciting a material to generate a polariton wave having a polariton wave frequency;

directing the beam to interact with the polariton wave and cause at least a portion of the beam to shift in frequency by an amount corresponding to the polariton wave frequency; and

adjusting the polariton wave frequency to cause a corresponding adjustment to the frequency shift,

wherein the optical excitation of the polariton wave comprises forming an optical excitation grating pattern in the material.

42. The method of claim 41, wherein the adjustment of the polariton wave frequency comprises applying an external electric field to the material.

43. The method of claim 41, wherein the material defines a polariton wave cavity resonant with the polariton wave frequency.

44. A method for shifting the frequency of an electromagnetic beam, the method comprising:

providing a material defining an array of polariton cavities having different resonant polariton wave frequencies;

generating a polariton wave in the cavity corresponding to a selected polariton wave frequency; and

directing the beam to interact with the polariton wave and cause at least a portion of the beam to shift in frequency by an amount corresponding to the polariton wave frequency.

45. A method for shifting the frequency of an electromagnetic beam, the method comprising:

selecting a polariton wave frequency based on a desired frequency shift for the electromagnetic beam;

optically exciting a material to generate a polariton wave having the selected polariton wave frequency; and

directing the beam to interact with the polariton wave and cause at least portion of the beam to shift in frequency by an amount corresponding to the polariton wave frequency,

wherein the optical excitation of the polariton wave comprises directing at least one pulse of optical radiation to the material, and wherein the optical pulse has a pulse duration shorter than the inverse of the polariton wave frequency.

46. A method for shifting the frequency of an electromagnetic beam, the method comprising:

optically exciting a material to generate a polariton wave having a polariton wave frequency;

directing the beam to interact with the polariton wave and cause at least a portion of the beam to shift in frequency by an amount corresponding to the polariton wave frequency; and

adjusting the polariton wave frequency to cause a corresponding adjustment to the frequency shift,

wherein the optical excitation of the polariton wave comprises directing at least one pulse of optical radiation to the material, and wherein the optical pulse has a pulse duration shorter than the inverse of the polariton wave frequency.

47. The method of claim 46, wherein the adjustment of the polariton wave frequency comprises applying an external electric field to the material.

48. The method of claim 46, wherein the material defines a polariton wave cavity resonant with the polariton wave frequency.