Small-Pitch Wire Grid Polarizer

Abstract

The wire grid polarizer (WGP) comprises an array of parallel, elongated nanostructures located over a surface of a transparent substrate and a plurality of spaces, including a space between adjacent nanostructures. Each of the nanostructures can include (1) a plurality of parallel, elongated wires located on the substrate, including an inner-pair located between an outer-pair; (2) lateral-gaps between each wire of the outer-pair and an adjacent wire of the inner-pair; (3) and a center-gap between the two wires of the inner-pair.

What is claimed is: 
     
         1 . A wire grid polarizer (WGP) comprising:
 a. an array of parallel, elongated nanostructures located over a surface of a transparent substrate, each of the nanostructures including:
 i. an elongated base-rib located over the substrate and having a distal-surface located away from the substrate; 
 ii. a plurality of parallel, elongated wires located on the distal-surface of the base-rib, including an inner-pair located between an outer-pair, wherein the wires are laterally oriented and spaced apart with respect to one another and each wire has a proximal-end closer to the substrate and a distal-end farther from the substrate and a thickness defined as a distance from the proximal-end to the distal-end; 
 iii. lateral-gaps between each wire of the outer-pair and an adjacent wire of the inner-pair, wherein each lateral-gap includes a lateral-solid-material-free-region extending from the distal-end towards the proximal-end for a distance of at least 25% of the thickness of a wire of the inner-pair, adjacent to the lateral-gap; and 
 iv. a center-gap between the wires of the inner-pair, wherein the center-gap includes a center-solid-material-free-region extending from the distal-end towards the proximal-end for a distance of at least 25% of the thickness of one of the wires of the inner-pair; and 
   b. a plurality of spaces, including a space between adjacent nanostructures, wherein each space includes an inter-nanostructure solid-material-free-region extending from the distal-end to the proximal-end, and beyond the proximal-end for a distance of at least 25% of the thickness of at least one of the wires of the outer-pair that adjoins the space.   
     
     
         2 . The WGP of  claim 1 , wherein:
 a. each of the nanostructures further includes an array of parallel, elongated rods, including a rod associated with each wire;   b. each rod is located between the substrate and the wire it is associated with; and   c. the rods are separated from each other by the lateral-solid-material-free-regions, the center-solid-material-free-regions, and the inter-nanostructure solid-material-free-regions.   
     
     
         3 . The WGP of  claim 1 , wherein:
 a. the lateral-solid-material-free-region extends from the distal-end towards the proximal-end for a distance of between 70% and 98% of the thickness of a wire of the inner-pair, adjacent to the lateral-gap; and   b. the center-solid-material-free-region extends from the distal-end towards the proximal-end for a distance of between 70% and 98% of the thickness of at least one of the wires of the inner-pair.   
     
     
         4 . The WGP of  claim 1 , wherein the center-solid-material-free-region extends from the distal-end to the proximal-end, and beyond the proximal-end for a distance of at least 10% of the thickness of at least one of the wires of the inner-pair. 
     
     
         5 . The WGP of  claim 1 , further comprising a support-rib between the two wires of the inner-pair, wherein the support-rib extends between 5% and 75% of a distance from the proximal-end towards the distal-end of at least one of the wires of the inner-pair. 
     
     
         6 . The WGP of  claim 1 , wherein:
 a. the plurality of parallel, elongated wires also include a middle-pair;   b. the wires of each middle-pair are laterally oriented with respect to one another, to the inner-pair, and to the outer-pair;   c. each wire of the middle-pair
 i. is located between a wire of the inner-pair and a wire of the outer-pair; 
 ii. is separated from the other wire of the middle-pair by wires of the inner-pair and by the center-gap; and 
 iii. extends between 5% and 75% of a distance from the proximal-end towards the distal-end of at least one of the wires of the inner-pair, adjacent to the middle-pair. 
   
     
     
         7 . The WGP of  claim 6 , wherein at least one of the following is reflective and at least one of the following is absorptive: the inner-pair, the middle-pair, and the outer-pair. 
     
     
         8 . The WGP of  claim 1 , wherein a chemical composition of the inner-pair is different from a chemical composition of the outer-pair, 
     
     
         9 . The WGP of  claim 1 , wherein widths of the lateral-gaps, the center-gap, and the space all differ from one another 
     
     
         10 . The WGP of  claim 1 , wherein:
 a. the plurality of parallel, elongated wires also include a second-outer-pair;   b. wires of the second-outer-pair are laterally oriented with respect to one another, to the inner-pair, and to the outer-pair;   c. wires of the second-outer-pair are located to sandwich the inner-pair and the outer-pair; and   d. each wire of the second-outer-pair is separated from the other wire of the second-outer-pair by wires of the outer-pair, wires of the inner-pair, and the center-gap.   
     
     
         11 . A wire grid polarizer (WGP) comprising:
 a. an array of parallel, elongated nanostructures located over a surface of a transparent substrate, each of the nanostructures including:
 i. a plurality of parallel, elongated wires located on the substrate, including an inner-pair located between an outer-pair, wherein the wires are laterally oriented and spaced apart with respect to one another and each wire has a proximal-end closer to the substrate and a distal-end farther from the substrate and a thickness defined as a distance from the proximal-end to the distal-end; 
 ii. lateral-gaps between each wire of the outer-pair and an adjacent wire of the inner-pair, wherein each lateral-gap includes a lateral-solid-material-free-region extending from the distal-end towards the proximal-end for a distance of at least 25% of the thickness of a wire of at least one of the inner-pair, adjacent to the lateral-gap; and 
 iii. a center-gap between the wires of the inner-pair, wherein the center-gap includes a center-solid-material-free-region extending from the distal-end towards the proximal-end for a distance of at least 25% of the thickness of at least one of the wires of the inner-pair; 
   b. a plurality of spaces, including a space between adjacent nanostructures, wherein each space includes an inter-nanostructure solid-material-free-region extending from the distal-end towards the proximal-end for a distance of at least at least 25% of the thickness of at least one of the wires of the outer-pair that adjoins the space; and   c. widths of the lateral-gaps, the center-gap, and the space all being different from one another.   
     
     
         12 . The WGP of  claim 11 , wherein widths of the lateral-gaps, the center-gap, and the space all differ from one another by at least 5 nanometers. 
     
     
         13 . The WGP of  claim 11 , wherein a largest width of the lateral-gaps, the center-gap, and the space differ from a smallest width of the lateral-gaps, the center-gap, and the space by at least 50% of the smallest width. 
     
     
         14 . The WGP of  claim 11 , wherein widths of the lateral-gaps are smaller than the width of the center-gap and smaller than the width of the space. 
     
     
         15 . A method of making a wire grid polarizer (VVGP), the method comprising the following steps in order:
 a. providing an array of parallel, elongated support ribs located over a transparent substrate and spaces between the support ribs, the spaces being solid-material-free;   b. conformal coating the substrate and the support ribs with a first-layer while maintaining solid-material-free at least a portion of the spaces between the support ribs,   c. etching the first-layer to remove horizontal segments and leaving an array of inner-pairs of parallel, elongated wires along sides of the support ribs, each wire of each inner-pair being separate from the other wire of the inner-pair;   d. conformal coating the substrate and the support ribs with a second-layer while maintaining solid-material-free at least a portion of the spaces between the support ribs;   e. conformal coating the substrate and the support ribs with a third-layer while maintaining solid-material-free at least a portion of the spaces between the support ribs;   f. etching the third-layer to remove horizontal segments and leaving outer-pairs, wherein:
 i. the outer-pairs are an array of parallel, elongated wires along sides of the support ribs; 
 ii. each wire of each outer-pair is spaced apart with respect to the other wire of the outer-pair; and 
   ill. wires of each outer-pair are spaced apart with respect to wires of the inner-pair by wires of a middle-pair, the wires of the middle-pair being formed of material of the second-layer; and   g. etching the support ribs and the middle-pair to form:
 i. lateral-solid-material-free-regions between at least a portion of each wire of each outer-pair and at least a portion of an adjacent wire of the inner-pair; and 
 ii. center-solid-material-free-regions between at least a portion of the two wires of each inner-pair. 
   
     
     
         16 . The method of  claim 15 , wherein etching the first-layer includes etching into the substrate between inner-pairs and adjacent inner-pairs. 
     
     
         17 . The method of  claim 15 , further comprising the following after conformal coating the substrate and the support ribs with the second-layer: etching the second-layer to remove horizontal segments and leaving middle-pairs, the middle-pairs being an array of parallel, elongated wires, each wire of each middle-pair being separated from the other wire of the middle-pair by wires of the inner-pair. 
     
     
         18 . The method of  claim 15 , wherein etching the support ribs includes removing the support ribs and forming the center-solid-material-free-region from a distal-end of the inner-pair to a proximal-end of the inner-pair. 
     
     
         19 . The method of  claim 15 , further comprising etching the substrate between adjacent nanostructures, to form an array of parallel elongated base-ribs, an inner-pair and an outer-pair located on each base-rib. 
     
     
         20 . The method of  claim 15 , wherein the first-layer is reflective or absorptive, the third-layer is reflective or absorptive, and the second-layer is transparent.