Structures for polarization and beam control

Abstract

In certain aspects, the invention features articles that include a layer including a plurality of rows of a first material extending along a first direction, the rows being spaced apart from each other and a center of each adjacent row being separated by a distance less than a wavelength λ so that for radiation of wavelength λ propagating along a path through the layer, the layer has a first effective index of refraction, n 1 , for the radiation having a first polarization state and the layer has second effective index of refraction, n 2 , for the radiation having a second polarization state orthogonal to the first polarization state, where n 1 and n 2 are different, where a surface of the layer includes a plurality of trenches, the trenches extending along a second direction and being spaced apart from each other, where a center of each adjacent trench is separated by a distance more than wavelength λ, and the trenches are filled with a second material having a refractive index, n 3 , different from n 2 .

1 . An article, comprising: 
 a layer including a plurality of rows of a first material extending along a first direction, the rows being spaced apart from each other and a center of each adjacent row being separated by a distance less than a wavelength λ so that for radiation of wavelength λ propagating along a path through the layer, the layer has a first effective index of refraction, n 1 , for the radiation having a first polarization state and the layer has second effective index of refraction, n 2 , for the radiation having a second polarization state orthogonal to the first polarization state, where n 1  and n 2  are different,    where a surface of the layer includes a plurality of trenches, the trenches extending along a second direction and being spaced apart from each other, where a center of each adjacent trench is separated by a distance more than wavelength λ, and the trenches are filled with a second material having a refractive index, n 3 , different from n 2 .    
     
     
         2 . The article of  claim 1 , wherein the article is configured so that for radiation having wavelength λ incident on the layer along the path, the article transmits about 50% or more of the incident radiation having the first polarization state along a first direction and transmits about 50% or more of the incident radiation having the second polarization state along one or more directions non-parallel to the first direction.  
     
     
         3 . The article of  claim 2 , wherein the article is configured to diffract about 50% or more of radiation having wavelength λ and the second polarization state incident on the article along the path into one or more non-zero diffraction orders.  
     
     
         4 . The article of  claim 3 , wherein the article is configured to diffract about 10% or less of radiation having wavelength λ and the first polarization state incident on the article along the path into one or more non-zero diffraction orders.  
     
     
         5 . The article of  claim 3 , wherein the article is configured to transmit substantially all of the radiation having wavelength λ and the first polarization state incident on the article along the path along the zero order diffraction direction.  
     
     
         6 . The article of  claim 1 , wherein the center of each adjacent trench is separated by a distance of about 2λ or more.  
     
     
         7 . The article of  claim 1 , wherein the center of each adjacent trench is separated by a distance of about 20λ or less.  
     
     
         8 . The article of  claim 1 , wherein the center of each adjacent trench is separated by a distance of about 1 micrometer or more.  
     
     
         9 . The article of  claim 1 , wherein the center of each adjacent trench is separated by a distance of about 20 micrometers or less.  
     
     
         10 . The article of  claim 1 , wherein the rows of the first material are periodically spaced in a direction orthogonal to the first direction.  
     
     
         11 . The article of  claim 1 , wherein the center of each adjacent row of the first material is separated by a distance of about 400 nm or less.  
     
     
         12 . The article of  claim 1 , wherein the center of each adjacent row of the first material is separated by a distance of about 200 nm or less.  
     
     
         13 . The article of  claim 1 , wherein the center of each adjacent row of the first material is separated by a distance in a range from about 70 nm to about 300 nm.  
     
     
         14 . The article of  claim 1 , wherein the row of the first material have a rectangular, trapezoidal, oval, or convex hull profile.  
     
     
         15 . The article of  claim 1 , wherein the first and second directions are non-parallel.  
     
     
         16 . The article of  claim 15 , wherein the first and second directions are substantially orthogonal to each other.  
     
     
         17 . The article of  claim 1 , wherein the layer is form-birefringent for radiation at wavelength λ and n 1  corresponds to either the ordinary or extraordinary refractive index of the layer.  
     
     
         18 . The article of  claim 1 , wherein n 3  is approximately equal to n 1 .  
     
     
         19 . The article of  claim 1 , wherein the first material is a dielectric material.  
     
     
         20 . The article of  claim 1 , wherein the first material comprises at least one material selected from a group consisting of SiO 2 , SiN x , Si, Al 2 O 3 , ZrO 2 , Ta 2 O 5 , TiO 2 , HfO 2 , Nb 2 O 5 , and MgF 2 .  
     
     
         21 . The article of  claim 1 , wherein the first material is a nanolaminate material.  
     
     
         22 . The article of  claim 1 , wherein the second material is a dielectric material.  
     
     
         23 . The article of  claim 1 , wherein the first material comprises at least one material selected from a group consisting of SiO 2 , SiN x , Si, Al 2 O 3 , ZrO 2 , Ta 2 O 5 , TiO 2 , HfO 2 , Nb 2 O 5 , and MgF 2 .  
     
     
         24 . The article of  claim 1 , wherein the second material is a nanolaminate material.  
     
     
         25 . The article of  claim 1 , wherein the surface including the trenches has a rectangular, trapezoidal, oval, or convex hull profile.  
     
     
         26 . The article of  claim 1 , wherein λ is in a range from about 150 nm to about 5,000 nm.  
     
     
         27 . The article of  claim 1 , wherein λ is in a range from about 400 nm to about 700 nm.  
     
     
         28 . The article of  claim 1 , wherein λ is in a range from about 1,200 nm to about 1,700 nm.  
     
     
         29 . The article of  claim 1 , wherein the layer includes a plurality of rows of a third material extending along the first direction, the rows of the third material alternating with the rows of the first material and the first and third materials being different.  
     
     
         30 . The article of  claim 1 , wherein the third material has a refractive index at λ that is different from n 1 .  
     
     
         31 . The article of  claim 30 , herein the third material is a dielectric material.  
     
     
         32 . The article of  claim 1 , wherein the first and second polarization states are linear polarization states.  
     
     
         33 . The article of  claim 1 , wherein the layer has a thickness, t, that is about 1 micrometer or less.  
     
     
         34 . The article of  claim 1 , wherein the trenches have a depth, d, less than a thickness, t, of the layer.  
     
     
         35 . The article of  claim 1 , further comprising a substrate that supports the layer.  
     
     
         36 . The article of  claim 35 , wherein the substrate is a planar substrate.  
     
     
         37 . The article of  claim 35 , wherein the substrate is comprises an inorganic glass material.  
     
     
         38 . The article of  claim 35 , wherein the substrate is substantially transparent for radiation having wavelength λ.  
     
     
         39 . The article of  claim 35 , further comprising an anti-reflection film supported by the substrate.  
     
     
         40 . An apparatus, comprising: 
 a first element comprising the article of  claim 1;  and    a second element comprising the article of  claim 1 ,    wherein the elements are configured so that the apparatus splits an incident beam at wavelength λ into a pair of beams that emerge from the apparatus spatially separated from one another and propagating along substantially parallel paths.    
     
     
         41 . The article of  claim 40 , wherein the pair of beams are substantially polarized orthogonal to each other.  
     
     
         42 . An article, comprising: 
 a layer comprising a plurality of rows of a composite material alternating with rows of a second material, the rows of the composite material and the rows of the second material being arranged to form a diffraction grating, where the diffraction grating has a period greater than a wavelength λ and the composite material is form-birefringent for radiation at wavelength λ.    
     
     
         43 . The article of  claim 42 , wherein the second material has a refractive index at λ approximately equal to either the ordinary or extraordinary refractive index of the composite material at λ.  
     
     
         44 . An article, comprising: 
 a polarizing beam splitter comprising a layer of a material that is form birefringent for radiation having a wavelength λ, wherein the polarizing beam splitter is configured so that for radiation having wavelength λ incident on the polarizing beam splitter along a path, the polarizing beam splitter transmits about 50% or more of the incident radiation having a first polarization state along a first direction and transmits about 50% or more of the incident radiation having a second polarization state along one or more directions non-parallel to the first direction, where the first and second polarization states are orthogonal.    
     
     
         45 . The article of  claim 44 , wherein the polarizing beam splitter transmits about 80% or more of the incident radiation having the first polarization state along the first direction.  
     
     
         46 . The article of  claim 44 , wherein the polarizing beam splitter transmits about 80% or more of the incident radiation having the second polarization state along the one or more directions non-parallel to the first direction.  
     
     
         47 . The article of  claim 44 , wherein the polarizing beam splitter transmits about 80% or more of the incident radiation having the second polarization state along a single of the directions non-parallel to the first direction.  
     
     
         48 . The article of  claim 44 , wherein the layer of the material is in the form of a diffraction grating for radiation having wavelength λ.  
     
     
         49 . The article of  claim 48 , wherein the first direction corresponds to zeroth order diffraction of the diffraction grating.  
     
     
         50 . The article of  claim 48 , wherein the one or more directions non-parallel to the first direction correspond to non-zero order diffraction of the diffraction grating.