Light modulation employing fluid movement

1. A light modulator comprising:

a light guide to guide light;

a diffraction grating to couple out a portion of the guided light from the light guide using diffractive coupling, the diffraction grating being at a surface of the light guide; and

an index-matched fluid to be selectively moved both into contact with the diffraction grating to defeat the diffractive coupling and out of contact with the diffraction grating to facilitate the diffractive coupling to modulate the coupled out guided light, the index-matched fluid having a refractive index that is substantially matched with a refractive index of a material of the diffraction grating.

2. The light modulator of claim 1 , further comprising another fluid having a refractive index that is substantially mismatched with the refractive index of the diffraction grating material, the index-mismatched fluid being in contact with the diffraction grating when the index-matched fluid is out of contact with the diffraction grating, wherein contact between the index-mismatched fluid further facilitates the diffractive coupling.

3. The light modulator of claim 2 , wherein one of the index-matched fluid and the index-mismatched fluid is a polar fluid and the other of the index-matched fluid and the index-mismatched fluid is a non-polar fluid.

4. The light modulator of claim 1 , wherein the index-matched fluid is to be moved in a lateral direction from a side of the light guide when out of contact with the diffraction grating.

5. The light modulator of claim 1 , wherein the index-matched fluid is to be selectively moved by electrowetting.

6. The light modulator of claim 1 , further comprising a first electrode and a second electrode, the index-matched fluid to be selectively moved by electrowetting into contact with the diffraction grating upon application of a first voltage to the first electrode, the index-matched fluid to be moved by electrowetting out of contact with the diffraction grating upon application of a second voltage to the second electrode.

7. The light modulator of claim 6 , wherein the first electrode is located under the light guide and aligned with the diffraction grating and the second electrode is located laterally away from and to a side of the light guide.

8. The light modulator of claim 1 , wherein the light modulator is substantially transparent in a direction orthogonal to a direction in which the light is guided in the light guide.

9. An electronic display comprising the light modulator of claim 1 , wherein the modulated light coupled out by the diffraction grating is modulated light of a pixel of the electronic display.

10. A fluid-modulated electronic display comprising:

a backlight light guide to guide light from a light source;

a diffraction grating formed in a surface of the backlight light guide to couple out a portion of the guided light from the backlight light guide by diffractive coupling; and

a fluid to be moved both into contact with the diffraction grating to defeat the diffractive coupling and out of contact with the diffraction grating to facilitate the diffractive coupling to modulate the coupled out guided light, the fluid being substantially index-matched with a refractive index of a material of the diffraction grating, the fluid being moved laterally with respect to the backlight light guide,

wherein the coupled out portion of the guided light is directed toward a viewing direction to form a pixel of the fluid-modulated electronic display.

11. The fluid-modulated electronic display of claim 10 , further comprising another fluid having a refractive index that is substantially mismatched with the refractive index of the diffraction grating material, the index-mismatched fluid being in contact with the diffraction grating when the index-matched fluid is moved out of contact with diffraction grating, wherein contact between the index-mismatched fluid and the diffraction grating to further facilitate the diffractive coupling, and wherein one or both of the index-matched fluid and the index-mismatched fluid are moved by electrowetting.

12. The fluid-modulated electronic display of claim 10 , wherein the light source is to provide substantially monochromatic light to be coupled out of the backlight light guide by the diffraction grating using the diffractive coupling, the monochromatic light corresponding to a primary color of the fluid-modulated electronic display.

13. A method of light modulation using index-matched fluid motion, the method comprising:

guiding light in a light guide;

selectively moving an index-matched fluid both into contact and out of contact with a diffraction grating at a surface of the light guide, the index-matched fluid having a refractive index that substantially matches a refractive index of the diffraction grating; and

diffractively coupling out a portion of the guided light with the diffraction grating when the index-matched fluid is out of contact with the diffraction grating,

wherein diffractive coupling is substantially defeated and the guided light is not diffractively coupled out when the index-matched fluid is in contact with the diffraction grating to modulate the coupled out guided light.

14. The method of light modulation of claim 13 , further comprising selectively moving another fluid into contact with the diffraction grating when the index-matched fluid is moved out of contact with the diffraction grating, the other fluid having a refractive index that is substantially mismatched with the diffraction grating refractive index and being immiscible with the index-matched fluid.

15. The method of light modulation of claim 13 , wherein selectively moving the index-matched fluid employs electrowetting comprising applying a first voltage to a first electrode to move the index-matched fluid by electrowetting into contact with the diffraction grating; and applying a second voltage to a second electrode to move the index-matched fluid out of contact with the diffraction grating, wherein the index-matched fluid is selectively moved laterally with respect to the light guide.