Optical switching apparatus

• US 6,295,154 B1
• Filed: 05/12/1999
• Issued: 09/25/2001
• Est. Priority Date: 06/05/1998
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Forehand, David I., Laor, Herzel, Orcutt, John W., Dewa, Andrew S., Lin, Tsen-Hwang, Sisco, James A., Congdon, Philip A.
• Primary Examiner(s): SCHUBERG, DARREN E
• Application Number:
  US09/310,284
• Time in Patent Office: 867 Days
• Field of Search: 359/223, 359/224, 359/872, 385/18
• US Class Current: 359/223.1
• CPC Class Codes: G02B 26/085 the reflecting means being moved or deformed by electromagnetic means
• CPC Class Codes: G02B 26/101 with both horizontal and vertical deflecting means, e.g. raster or XY scanners colour television using laser beams scanning a display screen H04N9/3129
• CPC Class Codes: G02B 6/3512 the optical element being reflective, e.g. mirror
• CPC Class Codes: G02B 6/3518 the reflective optical element being an intrinsic part of a MEMS device, i.e. fabricated together with the MEMS device MEMS devices in general B81B; manufacture of MEM devices in general B81C; micromechanical devices controlling the direction of light G02B26/0833
• CPC Class Codes: G02B 6/3548 1xN switch, i.e. one input and a selectable single output of N possible outputs
• CPC Class Codes: G02B 6/3558 1xN switch, i.e. one input and a selectable single output of N possible outputs
• CPC Class Codes: G02B 6/3572 Magnetic force magnetic forces controlling reflecting elements in general G02B26/085; magneto-optic devices G02F1/09
• CPC Class Codes: G02B 6/358 Latching of the moving element, i.e. maintaining or holding the moving element in place once operation has been performed; includes a mechanically bistable system
• CPC Class Codes: G02B 6/3582 Housing means or package or arranging details of the switching elements, e.g. for thermal isolation
• CPC Class Codes: G02B 6/359 of the position of the moving element itself during switching, i.e. without monitoring the switched beams
• CPC Class Codes: Y10S 359/904 Micromirror

Abstract

An optical matrix switch station (1) is shown mounting a plurality of optical switch units (15, 17), each of which includes a mirror (29), moveable in two axes, for purpose of switching optical beams from one optical fiber to another. A mirror assembly (41) includes a single body of silicon comprising a frame portion (43), gimbals (45), mirror portion (47), and related hinges (55). Magnets (53, 54) and air coils (89) are utilized to position the central mirror surface (29) to a selected orientation. The moveable mirror and associated magnets along with control LED'"'"'s (71) are hermetically packaged in a header (81) and mounted with the air coils on mounting bracket (85) to form a micromirror assembly package (99) mounted in each optical switch unit.

Claims

1. Optical switching apparatus comprising,

a header having a bottom wall and upwardly extending side walls forming a recess, a platform formed along the side walls spaced above the bottom wall,

a micromirror formed from a single piece of material having an outer frame portion lying in a plane and supported on the platform, an intermediate rotational gimbals portion hinged to the frame portion and movable relative to the frame portion about a first axis and an inner rotational mirror portion having a reflective, upper face surface formed with a radius of curvature of at least 2 meters hinged to the gimbals portion for movement of the mirror portion relative to the gimbals portion about a second axis, at least one magnet attached to one of the rotational portions, and

at least one electromagnetic coil assembly disposed in close proximity to the mirror assembly for applying selected forces to the at least one magnet for causing desired movement of the gimbals portion and the mirror portion along the two axes to reflect an optical beam directed to the mirror portion in a selected direction.

2. Optical switching apparatus according to claim 1 in which the gimbals portion is hinged to the frame portion by a pair of hinges spaced apart along the first axis and the mirror portion is hinged to the gimbals portion by a pair of hinges spaced apart along the second axis.

3. Optical switching apparatus according to claim 1 in which the axes are disposed 90 degrees relative to one another.

4. Optical switching apparatus according to claim 1 further comprising a pair of magnets for driving movement of the gimbals portion disposed on spaced apart locations of the gimbals portion along the second axis and a pair of magnets for driving movement of the mirror portion disposed on spaced apart locations of the mirror portion along the first axis.

5. Optical switching apparatus according to claim 4 in which each magnet comprises a set of an upper magnet attached to an upper face surface of the respective gimbals portion and mirror portion and a lower magnet attached to a lower surface of the respective gimbals portion and mirror portion, the respective upper and lower magnets of a set being in alignment with each other.

6. Optical switching apparatus according to claim 4 further comprising a push-pull drive for exciting the magnets.

7. Optical switching apparatus according to claim 1 in which the at least one electromagnetic coil assembly is disposed in engagement with the bottom wall of the header, a respective coil assembly being in alignment with a location of each magnet.

8. Optical switching apparatus according to claim 1 further comprising a single magnet mounted on a lower face surface of the mirror portion.

9. Optical switching apparatus according to claim 1 in which the piece is formed of silicon.

10. Optical switching apparatus according to claim 9 in which the mirror portion has a lower face surface and both the upper and lower face surfaces are polished thereby providing improved surface flatness.

11. Optical switching apparatus according to claim 1 in which the header is ceramic and a glass window is attached to the header covering the recess, the glass window being attached with indium forming a hermetic seal with a selected atmosphere sealed in the recess.

12. Optical switching apparatus comprising:

a header having a bottom wall and upwardly extending side walls forming a recess, a platform formed along the side walls spaced above the bottom wall;

a micromirror formed from a single piece of material having an outer frame portion living in a plane and supported on the platform, an intermediate rotational gimbals portion hinged to the frame portion and moveable relative to the frame portion about a first axis and an inner rotational mirror portion having a reflective upper face surface hinged to the gimbals portion for movement of the mirror portion relative to the gimbals portion about a second axis, at least one magnet attached to one of the rotational portions;

at least one electromagnetic coil assembly disposed in close proximity to the mirror assembly for applying selected forces to the at least one magnet for causing desired movement of the gimbals portion and the mirror portion along the two axes to reflect an optical beam directed to the mirror portion in a selected direction, the at least one electromagnetic coil assembly disposed in engagement with the bottom wall of the header, a respective coil assembly being in alignment with each spaced apart magnet location, in which each coil assembly comprises a bobbin having a spool on which a coil is wound and an aluminum plate portion between the respective coil and the bottom wall of the header, the bobbins having a massive heat sink portion of heat conductive material relative to the respective coils on a side of the coils remote from the plate portion.

13. Optical switching apparatus according to claim 12 further comprising a flex circuit electrically connected to the coils and a mounting bracket formed of heat conductive material, the flex circuit received on the mounting bracket, the mounting bracket being relatively massive relative to the coil assemblies, the header mounted on the mounting bracket with the coil assemblies therebetween and heat conductive potting material disposed between the header on one side and the flex circuit and the mounting bracket on another side.

14. Optical switching apparatus comprising:

a header having a bottom wall and upwardly extending side walls forming a recess, a platform formed along the side walls spaced above the bottom wall;

a micromirror formed from a single piece of material having an outer frame portion lying in a plane and supported on the platform, an intermediate rotational gimbals portion hinged to the frame portion and moveable relative to the frame portion about a first axis and an inner rotational mirror portion having a reflective upper face surface hinged to the gimbals portion for movement of the mirror portion relative to the gimbals portion about a second axis, a single magnet attached to one of the rotational portions;

at least one electromagnetic coil assembly disposed in close proximity to the mirror assembly for applying selected forces to the at least one magnet for causing desired movement of the gimbals portion and the mirror portion along the two axes to reflect an optical beam directed to the mirror portion in a selected direction; and

a plurality of electromagnetic coil assemblies spaced apart adjacent to but out of alignment with the single magnet.

15. Optical switching apparatus comprising:

a header having a bottom wall and upwardly extending side walls forming a recess, a platform formed along the side walls spaced above the bottom wall;

a micromirror formed from a single piece of material having an outer frame portion lying in a plane and supported on the platform, an intermediate rotational gimbals portion hinged to the frame portion and moveable relative to the frame portion about a first axis, the gimbals portion hinged to the frame portion by a pair of hinges spaced apart along the first axis, and an inner rotational mirror portion having a reflective upper face surface hinged to the gimbals portion for movement of the mirror portion relative to the gimbals portion about a second axis, the mirror portion hinged to the gimbals portion by a pair of hinges spaced apart along the second axis, at least one magnet attached to one of the rotational portions the frame portion having spaced apart, inwardly extending stop tabs on either side of the first axis and the gimbals portion having an extension along the first axis fitting closely between the stop tabs to limit motion in the plane in which the gimbals portion lies;

at least one electromagnetic coil assembly disposed in close proximity to the mirror assembly for applying selected forces to the at least one magnet for causing desired movement of the gimbals portion and the mirror portion alone the two axes to reflect an optical beam directed to the mirror portion in a selected direction.

16. Optical switching apparatus according to claim 15 further comprising a projection formed on one of the stop tabs and the extension and extending toward the other of the stop tabs and the extension.

17. Optical switching apparatus comprising:

a header having a bottom wall and upwardly extending side walls forming a recess, a platform formed along the side walls spaced above the bottom wall;

a micromirror formed from a single piece of material having an outer frame portion lying in a plane and supported on the platform, an intermediate rotational gimbals portion hinged to the frame portion and moveable relative to the frame portion about a first axis, the gimbals portion hinged to the frame portion by a pair of hinges spaced apart along the first axis, and an inner rotational mirror portion having a reflective upper face surface hinged to the gimbals portion for movement of the mirror portion relative to the gimbals portion about a second axis, the mirror portion hinged to the gimbals portion by a pair of hinges spaced apart along the second axis, at least one magnet attached to one of the rotational portions the gimbals portion having spaced apart, inwardly extending stop tabs on either side of the second axis and the mirror portion having an extension along the second axis fitting closely between the stop tabs to limit motion in the plane in which the mirror portion lies;

at least one electromagnetic coil assembly disposed in close proximity to the mirror assembly for applying selected forces to the at least one magnet for causing desired movement of the gimbals portion and the mirror portion along the two axes to reflect an optical beam directed to the mirror portion in a selected direction.

18. Optical switching apparatus according to claim 17 further comprising a projection formed on one of the stop tabs and the extension and extending toward the other of the stop tabs and the extension.

19. Optical switching apparatus comprising:

a header having a bottom wall and upwardly extending side walls forming a recess, a platform formed along the side walls spaced above the bottom wall;

a micromirror formed from a single piece of material having an outer frame portion lying in a plane and supported on the platform, an intermediate rotational gimbals portion hinged to the frame portion and moveable relative to the frame portion about a first axis and an inner rotational mirror portion having a reflective upper face surface hinged to the gimbals portion for movement of the mirror portion relative to the gimbals portion about a second axis, at least one magnet attached to one of the rotational portions;

at least one electromagnetic coil assembly disposed in close proximity to the mirror assembly for applying selected forces to the at least one magnet for causing desired movement of the gimbals portion and the mirror portion along the two axes to reflect an optical beam directed to the mirror portion in a selected direction, the at least one electromagnetic coil assembly disposed in engagement with the bottom wall of the header, a respective coil assembly being in alignment with each spaced apart magnet location;

a mounting bracket formed of heat conductive material, the header mounted on the bracket, the bracket being formed with a first portion having a pair of spaced apart surfaces lying in respective planes which intersect each other;

a package having a bottom wall, the bottom wall having an upwardly extending mounting pad formed with a second portion having a pair of complimentary, spaced apart surfaces, one of the first and second portions forming a concave cradle and the other of the first and second portions forming a convex protrusion received in the cradle, the first and second portions being fixed to one another.

20. Optical switching apparatus according to claim 19, in which a bore is formed through the bracket intermediate to the spaced apart surfaces of the first portion and a threaded bore is formed between the pair of complementary, spaced apart surfaces of the second portion and the portions are fixed together by a threaded member received through the bore of the bracket and threaded into the threaded bore.

21. Optical switching apparatus comprising,

a header having a bottom wall and upwardly extending side walls forming a recess, a platform formed along the side walls spaced above the bottom wall,

a micromirror assembly formed from a single piece of material having an outer frame portion lying in a plane and supported on the platform, and intermediate rotational gimbals portion hinged to the frame portion and movable relative to the frame portion about a first axis, and an inner rotational mirror portion having a reflective upper face surface, hinged to the gimbals portion for movement of the mirror portion relative to the gimbals portion about a second axis, at least one magnet attached to one of the rotational portions, and

at least one electromagnetic coil assembly disposed in close proximity to the mirror assembly for applying selected forces to the at least one magnet for causing desired movement of the gimbals portion and the mirror portion along the two axes to reflect an optical beam directed to the mirror portion in a selected direction.

22. A micromirror comprising:

an outer frame portion;

a gimbals portion hinged to said frame portion and rotatable relative to said frame portion about a first axis;

a mirror portion hinged to said gimbals portion and rotatable relative to said gimbals portions about a second axis; and

cooperating surfaces to limit motion in the plane of said mirror portion.

23. The micromirror of claim 22, said frame, gimbals, and mirror portions formed from a single piece of material.

24. The micromirror of claim 22, said cooperating surfaces formed on said frame and said gimbals portions.

25. The micromirror of claim 24, said frame and gimbals portions being approximately 100 microns thick, and said cooperating surfaces spaced approximately 10 microns apart.

26. The micromirror of claim 22, said cooperating surfaces formed on said gimbals and said mirror portions.

27. The micromirror of claim 26, said gimbals and said mirror portions being approximately 100 microns thick, and said cooperating surfaces spaced approximately 10 microns apart.

28. The micromirror of claim 22, comprising:

a temporary bridge portion extending between said frame portion and said gimbals portion to limit relative rotation of said frame and gimbals portions during manufacturing of said micromirror.

29. The micromirror of claim 22, comprising:

a temporary bridge portion extending between said gimbals portion and said mirror portion to limit relative rotation of said gimbals and said mirror portions during manufacturing of said micromirror.

30. A micromirror comprising:

an outer frame portion;

a gimbals portion hinged to said frame portion and rotatable relative to said frame portion about a first axis;

a mirror portion hinged to said gimbals portion and rotatable relative to said gimbals portions about a second axis; and

at least one pair of magnets on said micromirror, each of said pair of magnets positioned opposite each other on a top and bottom face of one portion of said micromirror.

31. The micromirror of claim 30, each of said pair of magnets positioned opposite each other on a top and bottom face of said gimbals portion, to symmetrically distribute said pair of magnet'"'"'s mass about an axis of rotation between said frame and gimbals portions.

32. The micromirror of claim 30, each of said pair of magnets positioned opposite each other on a top and bottom face of said mirror portion, to symmetrically distribute said pair of magnet'"'"'s mass about an axis of rotation between said gimbals and mirror portions.

33. The micromirror of claim 30, said at least one pair of magnets on said micromirror comprising:

at least one first pair of magnets positioned opposite each other on a top and bottom face of said gimbals portion, to symmetrically distribute said first pair of magnet'"'"'s mass about an axis of rotation between said frame and gimbals portions; and

at least one second pair of magnets positioned opposite each other on a top and bottom face of said mirror portion, to symmetrically distribute said second pair of magnet'"'"'s mass about an axis of rotation between said gimbals and mirror portions.

34. The micromirror of claim 30, comprising:

cooperating surfaces to limit motion in the plane of said mirror portion.

35. The micromirror of claim 34, said frame and gimbals portions being approximately 100 microns thick, said cooperating surfaces spaced approximately 10 microns apart.

36. The micromirror of claim 30, said frame, gimbals, and mirror portions formed from a single piece of material.

37. The micromirror of claim 30, comprising:

a temporary bridge portion extending between said frame portion and said gimbals portion to limit relative rotation of said frame and gimbals portions during manufacturing of said micromirror.

38. The micromirror of claim 30, comprising:

a temporary bridge portion extending between said gimbals portion and said mirror portion to limit relative rotation of said gimbals and said mirror portions during manufacturing of said micromirror.