2-D diffraction grating for substantially eliminating polarization dependent losses

• US 6,801,354 B1
• Filed: 08/20/2002
• Issued: 10/05/2004
• Est. Priority Date: 08/20/2002
• Status: Active Grant

• Current Assignee: Silicon Light Machines Corporation (SCREEN Holdings Co., Ltd.)
• Original Assignee: Silicon Light Machines Corporation (SCREEN Holdings Co., Ltd.)
• Inventors: Payne, Alexander, Miller, Gregory
• Primary Examiner(s): Ben, Loha
• Application Number:
  US10/225,211
• Time in Patent Office: 777 Days
• Field of Search: 359/290, 359/291, 359/292, 359/293, 359/295, 359/298, 359/231, 359/233, 359/569, 359/572, 359/573, 385/19, 385/37, 385/140, 385/901
• US Class Current: 359/291
• CPC Class Codes: G02B 26/0808 by means of one or more diffracting elements
• CPC Class Codes: G02B 6/266 the optical element being an attenuator
• CPC Class Codes: G02B 6/29314 by moving or modifying the diffractive element, e.g. deforming
• CPC Class Codes: G02B 6/3516 the reflective optical element moving along the beam path, e.g. controllable diffractive effects using multiple micromirrors within the beam
• 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 6/357 Electrostatic force electrostatic forces controlling reflecting elements in general G02B26/0841

Abstract

A 2D diffraction grating light valve modulates an incident beam of light. A plurality of elements each have a reflective surface with their respective reflective surfaces substantially coplanar. Alternatively, the reflective surfaces of the plurality of elements lie within one or more parallel planes. The elements are supported in relation to one another. Preferably, a planar member includes a plurality of holes arranged in a symmetrical two-dimensional array and configured such that the holes substantially optically extend the elements. Alternatively, one or more elements substantially optically extends the plurality of holes. The planar member includes a light reflective planar surface that is parallel to the plane of the elements within a functional area of the device. The planar member is supported in relation to the elements. By applying an appropriate biasing voltage to the planar member, the planar member can be moved in a direction normal to the plane of the elements. When the planar member and the plurality of elements are in a first configuration, the 2D diffraction grating reflects the incident beam of light as a plane mirror. When the planar member and the plurality of elements are in a second configuration, the 2D diffraction grating diffract the incident beam of light. Preferably, the planar member is a membrane circumferentially coupled to a support structure.

Claims

1. A modulator for modulating an incident beam of light comprising:

a. a plurality of elements, each element including a light reflective planar surface with the light reflective surfaces of the plurality of elements lying in one or more parallel planes;

b. a substantially planar member including a plurality of holes, wherein the holes are positioned such that the plurality of holes substantially optically extend the plurality of elements, the planar member including a light reflective planar surface parallel to the one or more parallel planes of the plurality of elements within a functional area of the modulator; and

c. a support structure coupled to the plurality of elements and to the planar member to maintain a position of the planar member in relation to the plurality of elements and to enable movement of the planar member in a direction normal to the plane of the plurality of elements, and between a first modulator configuration wherein the planar member and the plurality of elements act to reflect the incident beam of light as a plane mirror, and a second modulator configuration wherein the planar member and the plurality of elements act to diffract the incident beam of light.

2. The modulator according to claim 1 wherein a surface area of the planar member and a surface area of the plurality of elements forms a predetermined ratio within the functional area of the modulator.

3. The modulator according to claim 2 wherein the predetermined ratio includes equal surface area of the plurality of elements and surface area of the planar member within the functional area of the modulator.

4. The modulator according to claim 1 wherein the one or more parallel planes of the plurality of elements and the planar surface of the planar member lie within planes separated by a distance equal to about m/4 times a particular wavelength of the incident beam of light within the functional area of the modulator, wherein m=an even whole number or zero when the modulator is in the first modulator configuration and m=an odd whole number when the modulator is in the second modulator configuration.

5. The modulator according to claim 1 further comprising means for applying an electrostatic force to the planar member to move the planar member in the direction normal to the one or more parallel planes of the plurality of elements.

6. The modulator according to claim 5 wherein the reflective surfaces of the plurality of elements and the reflective surface of the planar mcmber are formed by metallic layers deposited on upper surfaces of the plurality of elements and the planar member.

7. The modulator according to claim 6 wherein the means for applying electrostatic force includes a voltage supply coupled to the metallic layer of the planar member for applying a bias voltage to the planar member.

8. The modulator according to claim 1 wherein the planar member is formed of a deformable resilient material.

9. The modulator according to claim 1 wherein the number of holes in the planar member is equal to the number of elements.

10. The modulator according to claim 9 wherein a shape of the holes is the same as a shape of the elements and an area of the holes is larger than an area of the elements.

11. The modulator according to claim 10 wherein the shape of the holes and the shape of the elements substantially eliminates polarization dependent losses of the incident beam impinging on the modulator.

12. The modulator according to claim 10 wherein the shape of the holes and the elements is circular.

13. The modulator according to claim 10 wherein the incident light does not impinge normal to the one or more parallel planes, and the shape of the holes and the elements is elliptical.

14. The modulator according to claim 1 wherein the holes are arranged in a symmetrical two-dimensional array.

15. The modulator according to claim 14 wherein the two-dimensional array forms a square.

16. The modulator according to claim 14 wherein the two-dimensional array forms a hexagon.

17. The modulator according to claim 1 wherein the planar member is a membrane circumferentially coupled to the support structure.

18. The modulator according to claim 17 wherein the support structure includes a circular array of etched posts for circumferentially coupling the support structure to the membrane, wherein the plurality of elements are positioned within the circular array of posts.

19. A method of modulating an incident beam of light comprising:

a. causing the beam to impinge upon a plurality of elements, each element including a light reflective planar surface with the light reflective surfaces of the plurality of elements lying in one or more parallel planes, and to impinge upon a substantially planar member including a plurality of holes, wherein the holes are positioned such that the plurality of holes substantially optically extend the plurality of elements, the planar member including a light reflective planar surface parallel to the one or more parallel planes of the plurality of elements within a functional area of the modulator; and

b. moving the planar member in a direction normal to the one or more parallel planes of the plurality of elements, and between a first modulator configuration wherein the planar member and the plurality of elements act to reflect the incident beam of light as a plane mirror, and a second modulator configuration wherein the planar member and the plurality of elements diffract the incident beam of light.

20. A modulator for modulating an incident beam of light comprising:

a. means for causing the beam to impinge upon a plurality of elements, each element including a light reflective planar surface with the light reflective surfaces of the plurality of elements lying in one or more parallel planes, and to impinge upon a substantially planar member including a plurality of holes, wherein the holes are positioned such that the plurality of holes substantially optically extend the plurality of elements, the planar member including a light reflective planar surface parallel to the one or more parallel planes of the plurality of elements within a functional area of the modulator; and

b. means for moving the planar member in a direction normal to the one or more parallel planes of the plurality of elements, and between a first modulator configuration wherein the planar member and the plurality of elements act to reflect the incident beam of light as a plane mirror, and a second modulator configuration wherein the planar member and the plurality of elements diffract the incident beam of light.