Integrated tunable fabry-perot filter and method of making same

• US 6,836,366 B1
• Filed: 08/25/2000
• Issued: 12/28/2004
• Est. Priority Date: 03/03/2000
• Status: Expired due to Term

• Current Assignee: Axsun Technologies Incorporated
• Original Assignee: Axsun Technologies Incorporated
• Inventors: Miller, Michael F., Shanfield, Stanley R., Whitney, Peter S., Le, Minh Van, West, David B., Flanders, Dale C.
• Primary Examiner(s): Juba, Jr., John
• Application Number:
  US09/645,200
• Time in Patent Office: 1,586 Days
• Field of Search: 356/454, 356/506, 356/519, 359/577, 359/578, 359/291, 359/846, 359/847, 359/290, 359/223, 359/224, 359/900
• US Class Current: 359/578
• CPC Class Codes: G01J 3/26 using multiple reflection, e.g. Fabry-Perot interferometer, variable interference filters
• CPC Class Codes: G02B 26/00 Optical devices or arrangements for the control of light using movable or deformable optical elements control of light by modification of the optical properties of the media of the elements involved therein G02F1/00
• CPC Class Codes: G02B 26/001 based on interference in an adjustable optical cavity interference filters G02B5/28; devices or arrangements using multiple reflections in spectrometry or monochromators G01J3/26
• CPC Class Codes: G02B 26/02 for controlling the intensity of light G02B26/004 takes precedence
• CPC Class Codes: Y10S 359/90 Methods

Abstract

A tunable Fabry-Perot filter includes an optical cavity bounded by a stationary reflector and a deformable or movable membrane reflector. A second electrostatic cavity outside of the optical cavity includes a pair of electrodes, one of which is mechanically coupled to the movable membrane reflector. A voltage applied to the electrodes across the electrostatic cavity causes deflection of the membrane, thereby changing the length of the optical cavity and tuning the filter. The filter with the movable membrane can be formed by micro device photolithographic and fabrication processes from a semiconductor material in an integrated device structure. The membrane can include an inner movable membrane portion connected within an outer body portion by a pattern of tethers. The tether pattern can be such that straight or radial tethers connect the inner membrane with the outer body. Alternatively, a tether pattern with tethers arranged in a substantially spiral pattern can be used.

Claims

1. A tunable optical filter comprising:

a first reflective layer;

a second reflective layer;

a spacing layer between the first and second reflective layers defining a first cavity disposed between the first and second reflective layers, a thickness of the spacing layer defining a length of the first cavity, and a wavelength of filtered light exiting the filter being related to the length of the first cavity, at least one of the first and second reflective layers being movable to change the length of the first cavity; and

an electrode layer disposed spaced apart from both of the first and second reflective layers to define a second cavity external to the first cavity, a voltage being applicable across the second cavity to move the at least one of the first and second reflective layers, an optical port being a hole formed through the electrode layer, an optical axis of said filter extending through said first cavity, and said first and second cavities being arranged at different ordinates along said optical axis;

wherein the at least one of the first and second reflective layers comprises a membrane layer comprising;

an outer body portion; and

an inner movable membrane portion within the outer body portion, the inner movable membrane portion being movable along an axis of the inner movable membrane portion, said voltage being applicable between the electrode layer and the membrane layer.

2. The filter of claim 1 further comprising a first electrode coupled to the electrode layer and a second electrode coupled to the at least one of the first and second reflective layers, the voltage being applicable across the first and second electrodes.

3. The filter of claim 1 wherein the filter is a Fabry-Perot filter.

4. The filter of claim 1 wherein at least one of the first and second reflective layers comprises a curved surface.

5. The filter of claim 1 wherein at least one of the first and second reflective layers comprises a concave surface.

6. The filter of claim 1 wherein the flexures are formed in a substantially radial pattern between the outer body portion and the inner movable membrane portion.

7. The filter of claim 1 wherein flexures are formed in a substantially spiral pattern between the outer body portion and the inner movable membrane portion.

8. The filter of claim 1 wherein the filter comprises a silicon-on-insulator structure.

9. The filter of claim 1 wherein the spacing layer comprises a semiconductor layer.

10. The filter of claim 9 wherein the spacing layer comprises an oxide layer.

11. The filter of claim 1 wherein the spacing layer comprises an oxide layer.

12. The filter of claim 1 wherein the spacing layer comprises a plurality of posts on at least one of the first and second reflective layers.

13. The filter of claim 12 wherein the posts comprise metal.

14. The filter of claim 13 wherein the metal comprises gold.

15. The filter of claim 13 wherein the posts are bonded onto the one of the first and second reflective layers.

16. The filter of claim 13 wherein the posts are plated onto the one of the first and second reflective layers.

17. The filter of claim 1 wherein at least one of the first and second reflective layers comprises a reflective coating.

18. The filter of claim 17 wherein the reflective coating is applied over a semiconductor layer.

19. The filter of claim 1 further comprising a second spacing layer between the electrode layer and the one of the first and second reflective layers, the spacing layer defining a length of the second cavity.

20. The filter of claim 19 wherein the second spacing layer comprises a semiconductor layer.

21. The filter of claim 20 wherein the second spacing layer comprises an oxide layer.

22. The filter of claim 19 wherein the second spacing layer comprises an oxide layer.

23. A method of making an optical filter comprising:

forming a first reflective layer;

forming a second reflective layer;

forming a spacing layer between the first and second reflective layers, said spacing layer defining a first cavity disposed between the first and second reflective layers, a thickness of the spacing layer defining a length of the first cavity, and a wavelength of filtered light exiting the filter being related to the length of the first cavity, at least one of the first and second reflective layers being movable to change the length of the first cavity; and

forming an electrode layer disposed spaced apart from both of the first and second reflective layers to define a second cavity external to the first cavity, such that a voltage is applicable across the second cavity to move the at least one of the first and second reflective layers, an optical axis of said filter extending through said first cavity, and said first and second cavities being arranged at different ordinates along said optical axis;

forming an optical port hole through the electrode layer;

wherein forming the at least one of the first and second reflective layers comprises;

forming an outer body portion;

forming an inner movable membrane portion within the outer body portion, the inner movable membrane portion being movable along an axis of the inner movable membrane portion, said voltage being applicable between the electrode layer and the movable membrane portion.

24. The method of claim 23 further comprising:

forming a first electrode coupled to the electrode layer; and

forming a second electrode coupled to the at least one of the first and second reflective layers such that the voltage is applicable across the first and second electrodes.

25. The method of claim 23 wherein the filter is a Fabry-Perot filter.

26. The method of claim 23 wherein at least one of the first and second reflective layers is formed to include a curved surface.

27. The method of claim 23 wherein at least one of the first and second reflective layers is formed to include a concave surface.

28. The method of claim 23 wherein flexures are formed in a substantially radial pattern between the outer body portion and the inner movable membrane portion.

29. The method of claim 23 wherein flexures are formed in a substantially spiral pattern between the outer body portion and the inner movable membrane portion.

30. The method of claim 23 wherein the method comprises forming a silicon-on-insulator structure.

31. The method of claim 23 wherein forming the spacing layer comprises forming a semiconductor layer.

32. The method of claim 31 wherein forming the spacing layer comprises forming an oxide layer.

33. The method of claim 23 wherein forming the spacing layer comprises forming an oxide layer.

34. The method of claim 23 wherein forming the spacing layer comprises forming a plurality of posts on at least one of the first and second reflective layers.

35. The method of claim 34 wherein the posts are formed of metal.

36. The method of claim 35 wherein the metal comprises gold.

37. The method of claim 34 wherein forming the posts comprises bonding the posts onto the one of the firsthand second reflective layers.

38. The method of claim 34 wherein forming the posts comprises plating the posts onto the one of the first and second reflective layers.

39. The method of claim 23 wherein forming at least one of the first and second reflective layers comprises forming a reflective coating.

40. The method of claim 39 further comprising applying the reflective coating over a semiconductor layer.

41. The method of claim 23 further comprising forming a second spacing layer between the electrode layer and the one of the first and second reflective layers, the spacing layer defining a length of the second cavity.

42. The method of claim 41 wherein forming the second spacing layer comprises forming a semiconductor layer.

43. The method of claim 42 wherein forming the second spacing layer comprises forming an oxide layer.

44. The method of claim 41 wherein forming the second spacing layer comprises forming an oxide layer.