PIECEWISE LINEAR SPATIAL PHASE MODULATOR USING DUAL-MODE MICROMIRROR ARRAYS FOR TEMPORAL AND DIFFRACTIVE FOURIER OPTICS

• US 20030156315A1
• Filed: 02/20/2002
• Published: 08/21/2003
• Est. Priority Date: 02/20/2002
• Status: Active Grant

• Current Assignee: Board of Trustees of the Leland Stanford Junior University (Stanford Management Co.), Regents of the University of California (University of California)
• Original Assignee: Board of Trustees of the Leland Stanford Junior University (Stanford Management Co.), Regents of the University of California (University of California)
• Inventors: Li, Kebin, Krishnamoorthy, Uma, Cornett, Kimberly T., Solgaard, Olav, Heritage, Jonathan P.
• Granted Patent: US 6,643,053 B2
• Time in Patent Office: Days
• US Class Current: 359/290
• CPC Class Codes: G02B 26/06 for controlling the phase of light G02B26/08 takes precedence , measuring optical phase difference G01J9/00
• CPC Class Codes: G02B 26/0833 the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD G02B26/0825 takes precedence; micromechanical devices in general B81B

Abstract

One embodiment of the present invention provides a spatial light phase modulator, which can perform piecewise linear phase modulation of a light beam. This spatial light phase modulator includes an array of movable micromirrors and an array of actuators. Each actuator of the array of actuators is movably coupled to one micromirror of the array of movable micromirrors and can move the micromirror both vertically and rotationally. Additionally, the present invention provides an optical function generator that is a femtosecond pulse shaper. This optical function generator includes a diffraction grating that disperses an input pulse into a dispersed spectrum, a lens assembly to focus the dispersed spectrum onto a micromirror array, and the micromirror array to provide spatial filtering to the dispersed spectrum to provide the filtered spectrum.

Claims

1. A spatial light phase modulator, wherein the spatial light phase modulator can perform piecewise linear phase modulation of a light beam, comprising:

a linear array of movable micromirrors; and

an array of actuators, wherein an actuator of the array of actuators is movably coupled to a micromirror of the linear array of movable micromirrors, and wherein the actuator can move the micromirror both vertically and rotationally.

2. The spatial light phase modulator of claim 1, wherein control signals applied to the array of actuators can cause the linear array of movable micromirrors to act in concert to perform piecewise linear phase modulation of the light beam.

3. The spatial light phase modulator of claim 1, wherein vertical forces applied by the actuator can cause the micromirror to have a vertical range of motion of at least pi radians at a specified wavelength.

4. The spatial light phase modulator of claim 1, wherein the actuator includes one of:

a thermo-expansion actuator;

a piezoelectric actuator;

a magnoelectric actuator; and

a capacitive actuator.

5. An optical function generator, wherein the optical function generator is a femtosecond pulse shaper, comprising:

a diffraction grating, wherein the diffraction grating disperses an input pulse into a dispersed spectrum;

a lens assembly; and

a micromirror array;

wherein the lens assembly focuses the dispersed spectrum onto the micromirror array, and wherein the micromirror array provides spatial filtering to the dispersed spectrum to provide a filtered spectrum.

6. The optical function generator of claim 5;

wherein the lens assembly focuses the filtered spectrum on the diffraction grating; and

wherein the diffraction grating combines the filtered spectrum into an output pulse.

7. The optical function generator of claim 5, further comprising a plurality of actuators movably coupled to the micromirror array, wherein an actuator of the plurality of actuators can move a mirror of the micromirror array in both elevation and tilt.

8. The optical function generator of claim 7, wherein the actuator includes one of:

a thermo-expansion actuator;

a piezoelectric actuator;

a magnoelectric actuator; and

a capacitive actuator.

9. A two-dimensional coherent mirror array, comprising:

a two-dimensional micromirror array; and

a plurality of actuators movably coupled to the two-dimensional micromirror array, wherein a micromirror of the two-dimensional micromirror array is movably coupled to a triad of actuators of the plurality of actuators, and wherein the triad of actuators are positioned such that the micromirror can be elevated and tilted in any direction.

10. The two-dimensional coherent mirror array of claim 9, wherein vertical forces applied by the triad of actuators can cause the micromirror to have a vertical range of motion of at least pi radians at a specified wavelength.

11. The two-dimensional coherent mirror array of claim 9, wherein an actuator of the plurality of actuators includes one of:

a thermo-expansion actuator;

a piezoelectric actuator;

a magnoelectric actuator; and

a capacitive actuator.

12. A programmable micromirror array, comprising:

an at least one movable micromirror;

a first movable comb fixedly coupled to a first edge of a movable micromirror within the at least one movable micromirror; and

a second movable comb fixedly coupled to a second edge opposite of the first edge of the movable micromirror;

wherein the first movable comb and the second movable comb form a movable portion of an interdigitated actuator; and

wherein the movable portion of the interdigitated actuator can apply vertical and rotational motions to the movable micromirror.

13. The programmable micromirror array of claim 12, further comprising:

a first folded spring coupled to the distal end of the first movable comb, wherein the first folded spring provides restoring forces to the first movable comb; and

a second folded spring coupled to the distal end of the second movable comb, wherein the second folded spring provides restoring forces to the second movable comb.

14. The programmable micromirror array of claim 12, wherein the interdigitated actuator further comprises:

a fixed lower actuator; and

a fixed upper actuator;

wherein the fixed lower actuator and the fixed upper actuator can apply vertical and rotational forces to the movable portion of the interdigitated actuator.

15. The programmable micromirror array of claim 14, wherein the fixed lower actuator includes planar capacitive drives.

16. The programmable micromirror array of claim 14, wherein the fixed upper actuator includes vertical comb drives.

17. The programmable micromirror array of claim 14, wherein vertical forces applied by the interdigitated actuator can cause the movable micromirror to have a vertical range of motion of at least pi radians at a specified wavelength.

18. A two-dimensional programmable micromirror array, comprising:

a plurality of movable micromirrors, wherein a micromirror of the plurality of movable micromirrors includes a hexagonal shape;

a first movable actuator fixedly coupled to a first edge of the micromirror;

a second movable actuator fixedly coupled to a second edge of the micromirror; and

a third movable actuator fixedly coupled to a third edge of the micromirror;

wherein the first movable actuator, the second movable actuator, and the third movable actuator are fixedly coupled to alternating edges of the micromirror, and

wherein the first movable actuator, the second movable actuator, and the third movable actuator act in concert to apply vertical and two-dimensional rotational motions to the micromirror.

19. The two-dimensional programmable micromirror array of claim 18, further comprising:

a first folded spring coupled to the distal end of the first movable actuator, wherein the first folded spring provides restoring forces to the first movable actuator;

a second folded spring coupled to the distal end of the second movable actuator, wherein the second folded spring provides restoring forces to the second movable actuator; and

a third folded spring coupled to the distal end of the third movable actuator, wherein the third folded spring provides restoring forces to the third movable actuator.

20. The two-dimensional programmable micromirror array of claim 18, further comprising three interdigitated actuators, wherein an interdigitated actuator includes:

a movable actuator, wherein the movable actuator includes one of the first movable actuator, the second movable actuator and the third movable actuator;

a fixed lower actuator; and

a fixed upper actuator;

wherein the fixed lower actuator and the fixed upper actuator can apply vertical and rotational forces to the movable actuator.

21. The two-dimensional programmable micromirror array of claim 20, wherein the fixed lower actuator includes planar capacitive drives.

22. The two-dimensional programmable micromirror array of claim 20, wherein the fixed upper actuator includes vertical comb drives.

23. The two-dimensional programmable micromirror array of claim 20, wherein vertical forces applied by the movable actuator can cause the micromirror to have a vertical range of motion of at least pi radians at a specified wavelength.

24. A method for creating a programmable micromirror, comprising:

receiving a substrate;

applying an insulating layer on the substrate;

depositing a plurality of lower actuators on the insulating layer;

applying a first sacrificial layer over the plurality of lower actuators and exposed portions of the insulating layer;

depositing a mirror assembly on the first sacrificial layer;

applying a second sacrificial layer over the mirror assembly and exposed portions of the first sacrificial layer;

creating a plurality of voids through the first sacrificial layer and the second sacrificial layer, wherein the insulating layer is exposed through the plurality of voids;

depositing a plurality of upper actuators on exposed portions of the insulating layer; and

removing the first sacrificial layer and the second sacrificial layer.

25. The method of claim 24, wherein the mirror assembly comprises:

a surface for the programmable micromirror;

a first movable comb; and

a second movable comb;

wherein the first movable comb and the second movable comb are fixedly coupled to opposite edges of the surface.

26. The method of claim 25,

wherein the first movable comb and the second movable comb form a movable portion of an interdigitated actuator;

and

wherein the interdigitated actuator can apply vertical and rotational motions to the mirror assembly.

27. The method of claim 26, wherein vertical forces applied by the interdigitated actuator can cause the programmable micromirror to have a vertical range of motion of at least pi radians at a specified wavelength.

28. The method of claim 25, further comprising:

creating a first folded spring at the distal end of the first movable comb; and

creating a second folded spring at the distal end of the second movable comb;

wherein the first folded spring and the second folded spring create restoring forces to the mirror assembly.

29. The method of claim 25, further comprising applying a reflective coating to the surface, wherein the reflective coating forms a mirror.

30. The method of claim 25,

wherein the mirror assembly includes a projection on a lower surface projecting toward the plurality of lower actuators;

and

wherein the projection prevents the mirror assembly from contacting the plurality of lower actuators.

31. The method of claim 24, wherein the mirror assembly comprises:

a hexagonal surface for the programmable micromirror;

a first movable comb;

a second movable comb; and

a third movable comb;

wherein the first movable comb, the second movable comb, and the third movable comb are fixedly coupled to alternating edges of the hexagonal surface.

32. The method of claim 31,

wherein the first movable comb, the second movable comb, and the third movable comb form a movable portion of an interdigitated actuator;

and

wherein the interdigitated actuator can apply vertical and two-dimensional rotational motions to the mirror assembly.

33. The method of claim 32, wherein vertical forces applied by the interdigitated actuator can cause the mirror assembly to have a vertical range of motion of at least pi radians at a specified wavelength.

34. The method of claim 31, further comprising:

creating a first folded spring at the distal end of the first movable comb;

creating a second folded spring at the distal end of the second movable comb; and

creating a third folded spring at the distal end of the third movable comb;

wherein the first folded spring, the second folded spring, and the third folded spring create restoring forces to the mirror assembly.

35. The method of claim 31, further comprising applying a reflective coating to the hexagonal surface, where the reflective coating forms a mirror.