Multi-layer absorptive wire grid polarizer

Abstract

A wire grid polarizer comprising an array of parallel, elongated first rib groups disposed over a substrate. Each first rib group can comprise a central first transmissive rib and a pair of first wires including a first wire disposed along each side of the first transmissive rib. A first dielectric material can substantially fill first gaps between each rib group and an adjacent rib group. An array of parallel, elongated second wires can be disposed over the rib groups and the first dielectric material. The first wires or the second wires can be absorptive and the other of the first wires or the second wires can be reflective.

What is claimed is: 
     
         1 . A wire grid polarizer comprising:
 a. a transmissive substrate;   b. an array of parallel, elongated first rib groups disposed over the substrate, each first rib group comprising:
 i. a central first transmissive rib; and 
 ii. a pair of first wires including a first wire disposed along each side of the first transmissive rib; 
   c. a first dielectric material substantially filling first gaps between each rib group and an adjacent rib group;   d. an array of parallel, elongated second wires disposed over the rib groups and the first dielectric material; and   e. the first wires or the second wires are absorptive and the other of the first wires or the second wires are reflective.   
     
     
         2 . The polarizer of  claim 1 , wherein the second wires are part of an array of parallel, elongated second rib groups, each second rib group comprising:
 a. a central second transmissive rib;   b. a pair of the second wires including a second wire disposed along each side of the second transmissive rib; and   c. second gaps between each second rib group and an adjacent second rib group.   
     
     
         3 . The polarizer of  claim 2 , further comprising second dielectric material substantially filling the second gaps. 
     
     
         4 . The polarizer of  claim 3 , wherein the second dielectric material extends from the first gaps above and over tops of the second rib groups and the second dielectric material is substantially transmissive to the incident light. 
     
     
         5 . The polarizer of  claim 1 , wherein:
 a. the first dielectric material extends from the gaps above and over tops of the rib groups and has a substantially flat, planar top-surface;   b. the first dielectric material is substantially transmissive to the incident light; and   c. the second wires are disposed on the top-surface of the first dielectric material.   
     
     
         6 . The polarizer of  claim 1 , wherein the first dielectric material forms separate first dielectric ribs, with a first dielectric rib in one first gap separate from a first dielectric rib in an adjacent first gap. 
     
     
         7 . The polarizer of  claim 6 , wherein:
 a. the first wires are reflective and the second wires are absorptive;   b. the first dielectric ribs absorptive;   c. a substantially flat, planar, transmissive dielectric layer is disposed between (i) tops of the first rib groups and tops of the first dielectric ribs and (ii) bottoms of the second wires.   
     
     
         8 . The polarizer of  claim 1 , wherein the first wires are absorptive and the second wires are reflective. 
     
     
         9 . The polarizer of  claim 1 , wherein the first wires are reflective and the second wires are absorptive. 
     
     
         10 . The polarizer of  claim 1 , wherein a pitch of the transmissive ribs is less than 150 nanometers. 
     
     
         11 . The polarizer of  claim 1 , wherein the polarizer transmits at least 90% of one polarization and absorbs at least 90% of an opposite polarization at a single wavelength of light. 
     
     
         12 . The polarizer of  claim 1 , wherein the polarizer transmits at least 90% of one polarization and absorbs at least 80% of an opposite polarization at all light wavelengths from 400 nm through 700 nm. 
     
     
         13 . A method of making a wire grid polarizer, the method comprising:
 a. providing a transmissive substrate having an array of parallel, elongated first transmissive ribs disposed over the substrate;   b. conformal coating the substrate and the first transmissive ribs with a first coating while maintaining solid-material-free first gaps between the first transmissive ribs;   c. etching the first coating to remove horizontal segments and leaving vertical first wires along sides of the first transmissive ribs, forming first rib groups each comprising a pair of first wires which sandwich a first transmissive rib;   d. backfilling the first gaps with first dielectric material;   e. forming a substantially flat, planar, top-surface above the first rib groups;   d. applying a continuous thin film of upper-material over the top-surface; and   f. etching the thin film of upper-material to form an array of parallel, elongated second wires disposed over the top-surface of the first dielectric material and solid-material-free second gaps between the second wires, and wherein the first wires or the second wires are absorptive and the other of the first wires or the second wires care reflective.   
     
     
         14 . The method of  claim 13 , wherein backfilling the first gaps and forming a substantially flat, planar top-surface further includes:
 a. backfilling above the first rib groups with the first dielectric material, the first dielectric material is substantially absorptive to the incident light and the first wires are reflective;   b. etching the first dielectric material and forming separate first dielectric ribs, with a first dielectric rib in one first gap separate from a first dielectric rib in an adjacent first gap; and   c. applying a transmissive dielectric layer over the first rib groups and the first dielectric ribs to form the substantially flat, planar top-surface with material of the transmissive dielectric layer.   
     
     
         15 . The method of  claim 13 , wherein backfilling the first gaps and forming a substantially flat, planar top-surface further includes backfilling above the first rib groups with the first dielectric material to form the substantially flat, planar top-surface with material of the first dielectric material. 
     
     
         16 . The method of  claim 13 , further comprising backfilling the second gaps with second dielectric material. 
     
     
         17 . The method of  claim 13 , wherein backfilling the second gaps further comprises backfilling above the second wires with second dielectric material. 
     
     
         18 . A method of making a wire grid polarizer, the method comprising:
 a. providing a transmissive substrate having an array of parallel, elongated first transmissive ribs disposed over the substrate;   b. conformal coating the substrate and the transmissive ribs with a first coating while maintaining solid-material-free first gaps between the first transmissive ribs;   c. etching the first coating to remove horizontal segments and leaving vertical first wires along sides of the first transmissive ribs, forming first rib groups each comprising a pair of first wires which sandwich a first transmissive rib;   d. backfilling the first gaps with first dielectric material;   e. forming a substantially flat, planar top-surface above the first rib groups;   f. etching the top-surface to form an array of parallel, elongated second transmissive ribs, the second transmissive ribs;   g. conformal coating the second transmissive ribs with a second coating while maintaining solid-material-free second gaps between the second transmissive ribs;   h. etching the second coating to remove horizontal segments and leaving vertical second wires along sides of the second transmissive ribs, forming second rib groups each comprising a pair of second wires which sandwich a second transmissive rib, and wherein the first wires or the second wires are absorptive and the other of the first wires or the second wires are reflective.   
     
     
         19 . The method of  claim 18 , further comprising backfilling the second gaps with second dielectric material substantially filling the second gaps and extending above the second rib groups. 
     
     
         20 . The method of  claim 18 , further comprising etching the second dielectric material and forming separate second dielectric ribs, with a second dielectric rib in one second gap separate from a second dielectric rib in an adjacent second gap.