Deformable grating apparatus for modulating a light beam and including means for obviating stiction between grating elements and underlying substrate

• US 5,459,610 A
• Filed: 05/20/1993
• Issued: 10/17/1995
• Est. Priority Date: 04/28/1992
• Status: Expired due to Term

• Current Assignee: Board of Trustees of the Leland Stanford Junior University (Stanford University)
• Original Assignee: Board of Trustees of the Leland Stanford Junior University (Stanford University)
• Inventors: Bloom, David M., Solgaard, Olav, Apte, Raj B., Sandejas, Francisco S. A.
• Primary Examiner(s): Ben, Loha
• Assistant Examiner(s): Juba, Jr., John
• Application Number:
  US08/062,688
• Time in Patent Office: 880 Days
• Field of Search: 359/213, 359/224, 359/226, 359/230, 359/231, 359/290, 359/291, 359/292, 359/295, 359/298, 359/299, 359/302, 359/558, 359/566, 359/569, 359/572, 359/573, 359/846, 359/855, 345/85, 345/108, 348/203
• US Class Current: 359/572
• CPC Class Codes: B81B 3/001 Structures having a reduced contact area, e.g. with bumps or with a textured surface
• CPC Class Codes: B81C 2201/115 Roughening a surface
• CPC Class Codes: G02B 26/0808 by means of one or more diffracting elements
• CPC Class Codes: G02B 5/1828 having means for producing variable diffraction controlling the direction of light by means of one or more diffracting elements G02B26/0808; acousto-optical elements G02F1/11, G02F1/33; electro- or magneto-optical diffraction G02F1/292, G02F1/2955
• CPC Class Codes: Y10S 359/90 Methods

Abstract

A modulator for modulating incident rays of light, the modulator comprising a plurality of equally spaced apart beam elements, each of which includes a light reflective planar surface. The elements are arranged parallel to each other with their light reflective surfaces parallel to each other. The modulator includes means for supporting the beam elements in relation to one another and means for moving the beam elements relative to one another so that the beams move between a first configuration wherein the modulator acts to reflect the incident rays of light as a plane mirror, and a second configuration wherein the modulator diffracts the incident rays of light as they are reflected therefrom. At least one of the facing surfaces of the beam elements and underlying substrate is configured to reduce any tendency to stick as they are pulled together. In operation, the light reflective surfaces of the beam elements remain parallel to each other in both the first and the second configurations and the perpendicular spacing between the reflective surfaces of adjacent beam elements is equal to m/4 times the wavelength of the incident rays of light, wherein m=an even whole number or zero when the beam elements are in the first configuration and m=an odd number when the beam elements are in the second configuration.

Claims

1. A modulator for modulating a beam of incident light, the modulator comprising;

a substrate having an upper surface;

a first planar light reflective surface formed on the upper surface of the substrate;

a deformable grating disposed above said first reflecting surface in spaced apart relation thereto and having a second planar light reflective surface formed on its upper side facing away from the upper surface of the substrate, the deformable grating being arranged with said second reflective surface parallel to and spaced from the upper surface of the substrate, said deformable grating having a lower surface disposed in spaced apart facing relationship to said upper surface of the substrate;

means for moving the grating towards the upper surface of the substrate while at the same time maintaining the second reflective surface of the grating substantially parallel to the first reflective surface; and

means for limiting the area of contact between said lower surface and said upper surface, and preventing the grating from sticking to the substrate when the grating is moved towards the upper surface of the substrate;

whereby, when the perpendicular spacing between the respective first and second reflective surfaces is equal to m/4 times the wavelength of the incident light bean and m=an even whole number or zero the modulator acts to reflect the incident light beam as a plane mirror and when m=an odd whole number the modulator diffracts the incident light beam as it reflects it, thereby providing the modulation of the light beam.

2. A modulator as recited in claim 1, wherein the grating comprises a plurality of equally sized and equally spaced apart parallel rectangular grating elements.

3. A modulator as recited in claim 2, wherein the grating has an underside facing the substrate and the means for preventing the grating from sticking to the substrate includes spacer elements positioned between the underside of the grating facing the substrate and the substrate.

4. A modulator as recited in claim 3, wherein the spacing between the first reflective surface formed on the substrate and the second reflective surface of the deformable grating is equal to half the wavelength of the incident light beam.

5. A modulator as recited in claim 4, wherein the means for moving the grating towards the upper surface of the substrate comprises means for applying an electrostatic force between the substrate and the grating.

6. A modulator as recited in claim 5, wherein the means for preventing the grating from sticking to the upper surface of the substrate includes at least one spacer element attached to each rectangular grating element.

7. A modulator as recited in claim 6, wherein the spacer elements are located at the edges of their associated rectangular grating elements.

8. A modulator as recited in claim 5, wherein the means for preventing the grating from sticking to the upper surface of the substrate includes at least one spacer element attached to the substrate and arranged to protrude into the space between the substrate and the underside of the grating.

9. A modulator for modulating a beam of incident light, comprising;

means forming a first planar light reflective surface;

a grating having means forming a plurality of second planar light reflective surfaces, the grating being arranged with its second reflective surfaces lying in a plane parallel to and spaced from the first planar reflective surface in a direction normal thereto, said grating having means forming third surfaces on the sides opposite to said second surfaces and facing said first surface, at least one of said first and third surfaces having means for preventing said grating from sticking to said first reflective surface in the event one engages the other; and

means for moving the grating in a direction normal to said first planar reflective surface and into engagement therewith, the second reflective surfaces of the grating remaining generally parallel to the first planar reflective surface;

whereby, when the spacing between the respective first and second light reflective surfaces is equal to m/4 times a particular wavelength of the incident light beam and m=an even whole number or zero, the modulator acts to reflect the incident light beam as a plane mirror, and when m=an odd whole number the modulator diffracts the incident light beam as it reflects it, thereby providing modulation of the light beam.

10. A modulator as recited in claim 9 wherein the grating comprises a plurality of equally sized and equally spaced apart parallel rectangular grating elements.

11. A modulator as recited in claim 10, wherein the means for preventing the grating from sticking to the first reflective surface includes spacer elements positioned between the third surfaces of the grating and the first reflective surface.

12. A modulator as recited in claim 11, wherein the spacing between the first reflective surface and the second reflective surface of the grating is equal to half the wavelength of the incident light beam.

13. A modulator as recited in claim 12, wherein the means for moving the grating into engagement with the first reflective surface comprises means for applying an electrostatic force between the first reflective surface and the grating.

14. A modulator as recited in claim 13, wherein the means for preventing the grating from sticking to said first reflective surface includes at least one spacer element attached to each rectangular grating element.

15. A modulator as recited in claim 14, wherein said grating includes a plurality of elongated rectangular grating elements and the spacer elements are located at the edges of associated rectangular grating elements.

16. A modulator as recited in claim 13, wherein the means for preventing the grating from sticking to the first reflective surface includes at least one spacer element attached to the first reflective surface and arranged to protrude into the space between the first reflective surface and the underside of the grating.