Symmetric Cube Polarizing Beam Splitter

Abstract

A cube polarizing beam splitter (PBS) can have one or more of the following characteristics: high contrast (Tp/Ts), acceptance of a large range of incident angles, broadband, and symmetry. The cube PBS can include a pair of wire-grid polarizers sandwiched between a first prism and a second prism. There can be a boundary layer between the wire-grid polarizers. An optical path length of a transmitted beam can be equal or very close to an optical path length of a reflected beam.

What is claimed is: 
     
         1 . A cube polarizing beam splitter (PBS) comprising:
 a pair of prisms including a first prism and a second prism;   a pair of wire-grid polarizers, including: a first wire-grid polarizer comprising an array of elongated wires, defining a first array, on a first substrate; and a second wire-grid polarizer comprising an array of elongated wires, defining a second array, on a second substrate;   the first and second wire-grid polarizers sandwiched between the first prism and the second prism; and   the first array and the second array are sandwiched between the first substrate and the second substrate.   
     
     
         2 . The cube PBS of  claim 1 , further comprising a boundary layer between the first wire-grid polarizer and the second wire-grid polarizer, wherein the boundary layer is an adhesive-free optical bond. 
     
     
         3 . The cube PBS of  claim 1 , further comprising a boundary layer between the first wire-grid polarizer and the second wire-grid polarizer, wherein the boundary layer is a layer of adhesive binding the first wire-grid polarizer to the second wire-grid polarizer. 
     
     
         4 . The cube PBS of  claim 1 , further comprising a boundary layer between the first wire-grid polarizer and the second wire-grid polarizer, wherein the boundary layer has a minimum thickness of at least 0.1 micrometer. 
     
     
         5 . The cube PBS of  claim 1 , further comprising a boundary layer between the first wire-grid polarizer and the second wire-grid polarizer, wherein the boundary layer has a maximum thickness of less than 100 micrometers. 
     
     
         6 . The cube PBS of  claim 1 , further comprising a boundary layer between the first wire-grid polarizer and the second wire-grid polarizer, wherein the boundary layer has a minimum thickness of at least 0.1 micrometer and a maximum thickness of less than 100 micrometers. 
     
     
         7 . The cube PBS of  claim 1 , further comprising a boundary layer between the first wire-grid polarizer and the second wire-grid polarizer, wherein the boundary layer adjoins the first array and the second array. 
     
     
         8 . The cube PBS of  claim 1 , wherein, for incident light across a wavelength range of 200 nanometers, with an angle of incidence on the pair of wire-grid polarizers from 25-65 degrees, contrast is at least 3000, where contrast=Tp/Ts, Tp=percent transmission of a predominantly transmitted polarization, and Ts=percent transmission of an opposite polarization. 
     
     
         9 . The cube PBS of  claim 1 , wherein, for incident light across a wavelength range of 300 nanometers, with an angle of incidence on the pair of wire-grid polarizers from 25-65 degrees, contrast is at least 3000, where contrast=Tp/Ts, Tp=percent transmission of a predominantly transmitted polarization, and Ts=percent transmission of an opposite polarization. 
     
     
         10 . The cube PBS of  claim 1 , wherein the cube PBS forms part of an image projector, the image projector comprising:
 a light source located to emit a beam of light into the cube PBS, the cube PBS separating the beam of light into a pair of polarized beams, including a desired beam and an additional beam, the desired beam having a higher light intensity than the additional beam, and emitting the desired beam out of the cube PBS; and   a spatial light modulator: located to receive the desired beam from the cube PBS; and having a plurality of pixels, each pixel capable of receiving a signal and transmitting or reflecting a portion of the desired beam without causing a change in polarization, or rotating a polarization of a portion of the desired beam, based on the signal, creating an image beam of selectively polarized light.   
     
     
         11 . The image projector of  claim 10 , further comprising a projection lens system, wherein the spatial light modulator and the projection lens system are oriented for the spatial light modulator to emit the image beam into the projection lens system and the projection lens system is capable of projecting an image. 
     
     
         12 . The cube PBS of  claim 1 , wherein wires of the first array and wires of the second array are laterally offset with respect to each other, defining a lateral-offset, such that a line through a center of a wire of the first array, perpendicular to a face of the first substrate, is laterally offset with respect to a line through a center of a wire of the second array closest to the wire of the first array, extending perpendicular to a face of the second substrate, and the lateral-offset is at least 3 nanometers. 
     
     
         13 . The cube PBS of  claim 1 , wherein:
 a plane of a surface of the first substrate on which the first array is located is parallel to a plane of a surface of the second substrate on which the second array is located; and   a length of the elongated wires of the first array is parallel to a length of the elongated wires of the second array.   
     
     
         14 . A cube polarizing beam splitter (PBS) comprising:
 a pair of prisms including a first prism and a second prism, a profile and dimensions of the first prism are the same as a profile and dimensions of the second prism;   a pair of wire-grid polarizers, including: a first wire-grid polarizer comprising an array of elongated wires, defining a first array, on a first substrate; and a second wire-grid polarizer comprising an array of elongated wires, defining a second array, on a second substrate;   the first and second wire-grid polarizers sandwiched between the first prism and the second prism;   the first array and the second array are sandwiched between the first substrate and the second substrate;   a boundary layer between and adjoining the first array and the second array; and   the cube PBS capable of polarizing a beam of light, wherein: the beam of light splits into a transmitted beam of light transmitting linearly through the cube PBS and through the pair of wire-grid polarizers and a reflected beam of light reflecting off of the pair of wire-grid polarizers; and |OPL T −OPL R |<300 micrometers where an optical path length is a distance of light travel through a material multiplied by an index of refraction of the material, OPL T  is an optical path length of the transmitted beam, and OPL R  is an optical path length of the reflected beam.   
     
     
         15 . The cube PBS of  claim 14 , wherein:
 a plane of a surface of the first substrate on which the first array is located is parallel to a plane of a surface of the second substrate on which the second array is located; and   a length of the elongated wires of the first array is parallel to a length of the elongated wires of the second array.   
     
     
         16 . The cube PBS of  claim 14 , wherein the boundary layer has a minimum thickness of at least 0.01 micrometer and a maximum thickness of less than 1 micrometer. 
     
     
         17 . A cube polarizing beam splitter (PBS) comprising:
 a pair of prisms including a first prism and a second prism;   a pair of wire-grid polarizers, including: a first wire-grid polarizer comprising an array of elongated wires, defining a first array, on a first substrate; and a second wire-grid polarizer comprising an array of elongated wires, defining a second array, on a second substrate;   the first and second wire-grid polarizers sandwiched between the first prism and the second prism;   the first array and the second array are sandwiched between the first substrate and the second substrate;   a boundary layer between and adjoining the first array and the second array; and   for incident light across a wavelength range of 300 nanometers, with an angle of incidence on the pair of wire-grid polarizers from 25-65 degrees, contrast is at least 3000, where contrast=Tp/Ts, Tp=percent transmission of a predominantly transmitted polarization, and Ts=percent transmission of an opposite polarization.   
     
     
         18 . The cube PBS of  claim 17 , wherein:
 a plane of a surface of the first substrate on which the first array is located is parallel to a plane of a surface of the second substrate on which the second array is located; and   a length of the elongated wires of the first array is parallel to a length of the elongated wires of the second array.   
     
     
         19 . The cube PBS of  claim 17 , wherein wires of the first array and wires of the second array are laterally offset with respect to each other, defining a lateral-offset, such that a line through a center of a wire of the first array, perpendicular to a face of the first substrate, is laterally offset with respect to a line through a center of a wire of the second array closest to the wire of the first array, extending perpendicular to a face of the second substrate. 
     
     
         20 . The cube PBS of  claim 17 , wherein the boundary layer has a minimum thickness of at least 0.01 micrometer and a maximum thickness of less than 1 micrometer.