Plasmon-based color tunable devices

Abstract

A color-tunable, reflective, paper-like display utilizes the unique optical properties of nano-engineered metal and metal-dielectric composite structures that exhibit a plasmon resonance. By changing the dielectric properties of a medium in which these structures are embedded, or by changing the spatial relationship of these structures, their optical absorbance and scattering spectra can be tuned. This enables simpler pixel architectures with better performance than is possible with fixed-color technologies. Low power video rate operation can be achieved in a paper-like display.

1 . A system comprising:
 a medium having dielectric properties that can be altered through application of an external stimulus;   a plurality of discrete structures adjacent to the medium, wherein each of the discrete structures have a plasmon resonance frequency that depends on the dielectric properties of the medium; and   a tuning system coupled to apply the external stimulus to the medium as needed to set the plasmon resonance to correspond to a desired frequency of light.   
   
   
       2 . The system of  claim 1 , wherein the medium comprises a liquid crystal. 
   
   
       3 . The system of  claim 1 , wherein the discrete structures comprise particles residing in the medium. 
   
   
       4 . The system of  claim 3 , wherein the particles comprise metal particles having diameters less than about 200 nm. 
   
   
       5 . The system of  claim 1 , wherein the discrete structure comprise features on a wall that is adjacent to the medium. 
   
   
       6 . A system comprising:
 a plurality of particles having plasmon resonances;   a plurality of tethers that in a relaxed state respectively hold the particles in surroundings having first dielectric properties;   a structure having second dielectric properties; and   a tuning system coupled to move the particles from the surroundings having the first dielectric properties to locations closer to the structure having the second dielectric properties, wherein moving the particles changes a frequency of the plasmon resonance.   
   
   
       7 . The system of  claim 6 , wherein the particles are treated to hold electric charge, and the tuning system comprises electrodes, wherein applying a voltage to the electrodes moves the particles. 
   
   
       8 . The system of  claim 6 , wherein the tethers are treated to hold electric charge, and the tuning system comprises electrodes, wherein applying a voltage to the electrodes moves the particles. 
   
   
       9 . The system of  claim 6 , wherein the surroundings comprises a dielectric fluid and the structure having the second dielectric properties comprises a film. 
   
   
       10 . The system of  claim 9 , wherein the film comprises a metal. 
   
   
       11 . The system of  claim 9 , wherein the film comprises a dielectric material having a dielectric constant that differs from a dielectric constant of the dielectric fluid. 
   
   
       12 . A system comprising:
 a plurality of particles including particles of a first type that have plasmon resonances;   a plurality of tethers, wherein multiple particles from the plurality of particles are attached to each tether; and   a tuning system coupled to control forces that alter shapes of the tethers and spacings between the particles attached to the tethers.   
   
   
       13 . The system of  claim 12 , wherein the tuning system comprises a system for controlling an electric field that acts on electric charge on the tethers. 
   
   
       14 . The system of  claim 12 , wherein the tuning system comprises a system for controlling an electric field that acts on electric charge on at least some of the particles. 
   
   
       15 . The system of  claim 12 , wherein altering the spacings between the particles changes the plasmon resonances of the particles of the first type by changing dielectric properties of surroundings of the particles of the first type. 
   
   
       16 . The system of  claim 12 , wherein the plurality of particles comprises particles of a second type, wherein the particles of the second type that differ from the particles of the first type. 
   
   
       17 . The system of  claim 16 , further comprising a fluid surrounding the tethers and the particles attached to the tethers, wherein the particles of the second type comprise a dielectric material having a dielectric constant that differs from a dielectric constant of the fluid. 
   
   
       18 . A system comprising:
 a compliant material;   a plurality of particles of a first type embedded in the compliant material, the particles having plasmon resonances; and   a tuning system coupled to control compression of the compliant material to thereby control relative spacing of the particles and frequencies of the plasmon resonances.   
   
   
       19 . The system of  claim 18 , wherein the tuning system comprises:
 a first plate on a surface of the compliant material;   a second plate on an opposite surface of the compliant material; and   a system for controlling a separation between the first and second plates.   
   
   
       20 . A system comprising:
 a first fluid;   a second fluid that is immiscible with the first fluid and positioned to have an interface with the first fluid;   a plurality of particles confined to the interface, the particles having plasmon resonances; and   a tuning system coupled to control spacing of the particles to thereby control relative spacing of the particles and frequencies of the plasmon resonances.   
   
   
       21 . The system of  claim 20 , wherein the particles are treated to hold electric charge and the tuning system comprises electrodes positioned for creation of electric fields that move the particles. 
   
   
       22 . A system comprising:
 a structure having discrete features with plasmon resonances;   a fluid adjacent to the surface of the structure;   a plurality of first particles in the fluid with dielectric properties that are different than those of the fluid; and   a tuning system coupled to move the particles relative to the structure and thereby control frequencies of the plasmon resonances.   
   
   
       23 . The system of  claim 22 , wherein the structure comprises a plate and the discrete features comprise second particles attached to the plate. 
   
   
       24 . The system of  claim 22 , wherein the structure comprises a plate with a contoured surface, wherein bumps on the surface form the discrete features. 
   
   
       25 . The system of  claim 22 , wherein the structure comprises a film, and the discrete features comprise regions of the film that are between adjacent holes in the film. 
   
   
       26 . The system of  claim 22 , wherein the structure comprises a film, and the discrete features comprise regions of the film that are between adjacent depressions in the film. 
   
   
       27 . The system of  claim 22 , wherein the particles in the fluid are transparent in a dispersed state in the fluid and are opaque when collected in a condensed state, the tuning system being capable of moving the particles from the dispersed state to the collected state. 
   
   
       28 . A system comprising:
 a structure having first dielectric properties;   a fluid adjacent to the surface of the structure, wherein the fluid has second dielectric properties that differ from the first dielectric properties;   a plurality of particles having plasmon resonances; and   a tuning system coupled to move the particles relative to the structure and thereby control frequencies of the plasmon resonances.   
   
   
       29 . The system of  claim 28 , wherein the particles are electrically charged and the tuning system moves the particles relative to the structure by applying an electric field. 
   
   
       30 . A system comprising:
 a plurality of particles that are non-spherical and have plasmon resonances; and   a tuning system coupled to control orientations of the particles relative to the electric field directions of incident light, where frequencies of the plasmon resonances that interact with the incident light depend on the orientations of the particles relative to the electric field directions of the incident light.   
   
   
       32 . The system of  claim 30 , wherein the tuning system comprises liquid crystal molecules, wherein application of an electric field to the liquid crystal molecules causes a change in state of the liquid crystal molecules that changes the orientations of the particles. 
   
   
       33 . A pixel structure comprising:
 a color-tunable layer having an apparent color that depends on a plasmon resonance in the color tunable layer;   a tuning system coupled to control a frequency of the plasmon resonance, the tuning system selecting the frequency from a frequency range;   a shutter in a stack with the color-tunable layer; and   a back plate in the stack.   
   
   
       34 . The structure of  claim 33 , wherein:
 the apparent color of the color tunable layer results from scattering light in a frequency band around the frequency of the plasmon resonance;   the shutter is a transparent-to-white shutter that is operable in a range of transparencies; and   the back plate is black.   
   
   
       35 . A pixel structure comprising:
 a first color-tunable layer having an apparent color that depends on a first plasmon resonance in the first color tunable structure;   a first tuning system coupled to control a first frequency of the first plasmon resonance, the first tuning system selecting the first frequency from a first frequency range;   a second color-tunable layer having an apparent color that depends on a second plasmon resonance in the second color tunable structure; and   a second tuning system coupled to control a second frequency of the second plasmon resonance, the second tuning system selecting the second frequency from a second frequency range.   
   
   
       36 . The structure of  claim 35 , further comprising:
 a first shutter and a first back plate in a first stack with the first color-tunable layer; and   a second shutter and a second back plate in a second stack with the second color-tunable layer, wherein the second stack is horizontally adjacent to the first stack.   
   
   
       37 . The structure of  claim 35 , wherein the first color-tunable layer overlies the second color-tunable layer in a stack. 
   
   
       38 . The structure of  claim 37 , wherein the stack further comprises a shutter and a back plate. 
   
   
       39 . The structure of  claim 38 , wherein the shutter comprises a transparent-black shutter, and back plate is white. 
   
   
       40 . The structure of  claim 38 , wherein the shutter comprises a transparent-white shutter, and back plate is black. 
   
   
       41 . A light shutter comprising:
 a plurality of discrete structures having a plasmon resonance with a width corresponding to a range of frequencies to be gated by the light shutter; and   a tuning system coupled to control a peak frequency of the plasmon resonance, the tuning system being capable of switching the peak frequency between a first frequency within the range and a second frequency outside the range.   
   
   
       42 . The light shutter of  claim 41 , wherein the range corresponds to visible frequencies of light.