Interferometric optical modulator with broadband reflection characteristics

Abstract

An optical device suitable for forming a pixel in a video display. The optical device includes a first layer having a first refractive index; a second layer over the first layer, the second layer having a second refractive index less than the first refractive index; and a third layer over the second layer, the third layer having a third refractive index larger than the second refractive index; and a fourth layer that is at least partially optically absorptive, wherein the optical stack and the fourth layer are a first distance from one another when the device is in a first state and are a second distance from one another when the device is in a second state, the first distance different from the second distance.

1 . An optical device comprising:
 an optical stack including
 a first layer having a first refractive index; 
 a second layer over the first layer, the second layer having a second refractive index less than the first refractive index; and 
 a third layer over the second layer, the third layer having a third refractive index larger than the second refractive index; and 
   a fourth layer that is at least partially optically absorptive,   wherein the optical stack and the fourth layer are a first distance from one another when the device is in a first state, the optical device reflecting substantially white light while in the first state, and are a second distance from one another when the device is in a second state, the first distance different from the second distance.   
     
     
         2 . The optical device of  claim 1 , wherein at least one of the first layer and the third layer includes two or more sub-layers. 
     
     
         3 . The optical device of  claim 2 , wherein one of the sub-layers has a fourth refractive index greater than the second refractive index. 
     
     
         4 . The optical device of  claim 2 , wherein one of the sub-layers is electrically conductive. 
     
     
         5 . The optical device of  claim 1 , wherein a region between the optical stack and the at least partially optically absorptive layer has a fifth refractive index that is less than the third refractive index. 
     
     
         6 . The optical device of  claim 1 , wherein at least one of the first layer and the third layer is electrically conductive. 
     
     
         7 . The optical device of  claim 1 , wherein the first refractive index and the third refractive index are both greater than about 1.7. 
     
     
         8 . The optical device of  claim 1 , wherein the second refractive index is less than about 1.5. 
     
     
         9 . The optical device of  claim 1 , wherein the first layer or third layer includes indium tin oxide, silicon nitride, titanium oxide, zirconium oxide, yttrium oxide, antimony oxide, or zinc selenide. 
     
     
         10 . The optical device of  claim 1 , wherein the second layer includes cryolite, magnesium fluoride, or fluorinated SiO x . 
     
     
         11 . The optical device of  claim 1 , wherein the fourth layer includes molybdenum, nickel, silicon, TiN x W y , titanium nitride, germanium, carbon, iron, chromium, tungsten, Si x Ge 1-x , or tin nitride. 
     
     
         12 . The optical device of  claim 1 , wherein the first layer has a thickness in a range between about 700 angstroms and about 1350 angstroms. 
     
     
         13 . The optical device of  claim 1 , wherein the second layer has a thickness in a range between about 900 angstroms and about 1400 angstroms. 
     
     
         14 . The optical device of  claim 1 , wherein the third layer has a thickness in a range between about 100 angstroms and about 550 angstroms. 
     
     
         15 . The optical device of  claim 1 , wherein the fourth layer has a thickness in a range between about 30 angstroms and about 3000 angstroms. 
     
     
         16 . The optical device of  claim 1 , wherein the first distance is in a range between about 1300 Å and about 2300 Å or between about 3000 Å and 4500 Å. 
     
     
         17 . The optical device of  claim 1 , wherein the second distance is approximately zero. 
     
     
         18 . The optical device of  claim 1 , wherein the optical device in the first state has a first reflectance and the optical device in the second state has a second reflectance, the ratio of the first reflectance to the second reflectance of the optical device being greater than about ten. 
     
     
         19 . The optical device of  claim 18 , wherein the ratio is greater than about one hundred. 
     
     
         20 . The optical device of  claim 1 , wherein the optical device in the first state has a reflected spectral power distribution of visible light which substantially corresponds to the standard white point D65. 
     
     
         21 . The optical device of  claim 1 , wherein the fourth layer is mounted on a mechanical support layer. 
     
     
         22 . The optical device of  claim 21 , wherein the mechanical support layer includes nickel. 
     
     
         23 . The optical device of  claim 1 , wherein the optical stack is mounted on an at least partially optically transmissive substrate. 
     
     
         24 . The optical device of  claim 23 , wherein the at least partially optically transmissive substrate includes glass. 
     
     
         25 . The optical device of  claim 1 , further comprising
 a display;   a processor that is configured to communicate with said display, said processor being configured to process image data; and   a memory device that is configured to communicate with said processor.   
     
     
         26 . The optical device of  claim 25 , further comprising a driver circuit configured to send at least one signal to said display. 
     
     
         27 . The optical device of  claim 26 , further comprising a controller configured to send at least a portion of said image data to said driver circuit. 
     
     
         28 . The optical device of  claim 25 , further comprising an image source module configured to send said image data to said processor. 
     
     
         29 . The optical device of  claim 28 , wherein said image source module includes at least one of a receiver, transceiver, and transmitter. 
     
     
         30 . The optical device of  claim 25 , further comprising an input device configured to receive input data and to communicate said input data to said processor. 
     
     
         31 . A method of forming an optical device, comprising:
 forming a first layer, the first layer having a first refractive, index;   forming a second layer over the first layer, the second layer having a second refractive index less than the first refractive index;   forming a third layer over the second layer, the third layer having a third refractive index larger than the second refractive index;   forming a sacrificial layer over the third layer;   forming a fourth layer that is at least partially optically absorptive over the sacrificial layer; and   removing the sacrificial layer,   wherein the optical device reflects substantially white light when the fourth layer is spaced apart from the third laver.   
     
     
         32 . The method of  claim 31 , wherein the first layer is formed on an optically transmissive substrate. 
     
     
         33 . (canceled) 
     
     
         34 . (canceled) 
     
     
         35 . (canceled) 
     
     
         36 . An optical device comprising:
 first means for reflecting and transmitting light, the first means having a first refractive index;   second means for reflecting and transmitting light, the second means over the first means, the second means having a second refractive index less than the first refractive index; and   third means for reflecting and transmitting light, the third means over the second means, the third means having a third refractive index larger than the second refractive index; and   fourth means for reflecting and absorbing light, wherein the third means and the fourth means are a first distance from one another when the device is in a first state, the optical device reflecting substantially white light while in the first state, and are a second distance from one another when the device is in a second state, the first distance different from the second distance.   
     
     
         37 . The optical device of  claim 36 , wherein the first means includes layer of material having the first refractive index, the second means includes a layer of material having the second refractive index, and third means includes a layer of material having the third refractive index. 
     
     
         38 . The optical device of  claim 36 , wherein the fourth means includes a layer of at least partially optically absorptive material.