Nonpolarizing beamsplitter
First Claim
1. A nonpolarizing beamsplitter, comprising a multilayered stack having two major surfaces, the multilayered stack comprising alternating layers of a first material and a second material, wherein each of the layers has an x-direction and a y-direction forming an x-y plane, and a z-direction perpendicular to the x-y plane, wherein the first material layers have an index of refraction in the x-y plane, n1(x,y) and an index of refraction in the z-direction n1(z), wherein the first material layers are uniaxially birefringent such that n1(x,y) -n1(z) ≧
- 0.05, wherein the second material layers have an index of refraction in the x-y plane, n2(x,y), and an index of refraction in the z-direction, n2(z), wherein n1(x,y) >
n2(x,y) and n1(z) ≦
n2(z), such that for an incident beam of light striking a major surface of the beamsplitter at any angle of incidence θ
within a range of angle of incidence, the incident beam having a useful bandwidth, a p-polarized component and an s-polarized component, the beamsplitter exhibits an average reflectivity Rp for the p-polarized component of the incident beam and an average reflectivity Rs for the s-polarized component of the incident beam, wherein Rp and Rs differ by less than 25%.
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Abstract
A nonpolarizing beamsplitter is provided, which includes a multilayered stack of alternating layers of a first material and a second material. The first material layers are uniaxially birefringent, and the second material layers are optionally uniaxially birefringent or isotropic. The layers have index of refraction relationships such that for an incident beam having a useful bandwidth, a p-polarized component and an s-polarized component striking the beamsplitter at any angle of incidence θ within a desired range, the beamsplitter exhibits substantially the same average reflectivity for the p-polarized component of the incident beam as for the s-polarized component. The invention also includes a method of making a nonpolarizing beamsplitter.
103 Citations
35 Claims
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1. A nonpolarizing beamsplitter, comprising a multilayered stack having two major surfaces, the multilayered stack comprising alternating layers of a first material and a second material, wherein each of the layers has an x-direction and a y-direction forming an x-y plane, and a z-direction perpendicular to the x-y plane, wherein the first material layers have an index of refraction in the x-y plane, n1(x,y) and an index of refraction in the z-direction n1(z), wherein the first material layers are uniaxially birefringent such that n1(x,y) -n1(z) ≧
- 0.05, wherein the second material layers have an index of refraction in the x-y plane, n2(x,y), and an index of refraction in the z-direction, n2(z), wherein n1(x,y) >
n2(x,y) and n1(z) ≦
n2(z), such that for an incident beam of light striking a major surface of the beamsplitter at any angle of incidence θ
within a range of angle of incidence, the incident beam having a useful bandwidth, a p-polarized component and an s-polarized component, the beamsplitter exhibits an average reflectivity Rp for the p-polarized component of the incident beam and an average reflectivity Rs for the s-polarized component of the incident beam, wherein Rp and Rs differ by less than 25%. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
- 0.05, wherein the second material layers have an index of refraction in the x-y plane, n2(x,y), and an index of refraction in the z-direction, n2(z), wherein n1(x,y) >
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25. A nonpolarizing beamsplitter, comprising a multilayered stack having two major surfaces, the multilayered stack comprising alternating layers of polyethylene napthalate and syndiotactic polystyrene, wherein each layer has a thickness of at least 5/4λ
- , wherein each of the layers has an x-direction and a y-direction forming an x-y plane, and a z-direction perpendicular to the x-y plane, wherein the polyethylene napthalate layers have an index of refraction in the x-y plane, n1(x,y), in the range from about 1.73 to about 1.77 and an index of refraction in the z-direction, n1(z), in the range from about 1.48 to about 1.52, wherein the syndiotactic polystyrene layers have an index of refraction in the x-y plane, n2(x,y), in the range from about 1.55 to about 1.59 and an index of refraction in the z-direction, n2(z), in the range from about 1.60 to about 1.64, wherein the indices of refraction are measured at 580 nm, such that for an incident beam of light striking a major surface of the beamsplitter at any angle of incidence θ
in the range extending from about 0°
to about 60°
, the incident beam having a useful bandwidth, a p-polarized component and an s-polarized component, the beamsplitter exhibits an average reflectivity Rp for the p-polarized component of the incident beam and an average reflectivity Rs for the s-polarized component of the incident beam, wherein Rp and Rs differ by less than 10%.
- , wherein each of the layers has an x-direction and a y-direction forming an x-y plane, and a z-direction perpendicular to the x-y plane, wherein the polyethylene napthalate layers have an index of refraction in the x-y plane, n1(x,y), in the range from about 1.73 to about 1.77 and an index of refraction in the z-direction, n1(z), in the range from about 1.48 to about 1.52, wherein the syndiotactic polystyrene layers have an index of refraction in the x-y plane, n2(x,y), in the range from about 1.55 to about 1.59 and an index of refraction in the z-direction, n2(z), in the range from about 1.60 to about 1.64, wherein the indices of refraction are measured at 580 nm, such that for an incident beam of light striking a major surface of the beamsplitter at any angle of incidence θ
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26. A method of making a nonpolarizing beamsplitter, comprising:
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coextruding a multilayered sheet of alternating layers of a first material and a second material, wherein each of the layers has an x-direction and a y-direction forming an x-y plane, and a z-direction perpendicular to the x-y plane, wherein the first material layers have an index of refraction in the x-y plane, n1(x,y), and an index of refraction in the z-direction, n1(z), and the second material layers have an index of refraction in the x-y plane, n2(x,y), and an index of refraction in the z-direction, n2(z), wherein the first material exhibits positive stress-induced birefringence; and biaxially stretching the sheet in the x-direction and the y-direction until a multilayered stack having two major surfaces is formed, wherein the first material layers are uniaxially birefringent such that n1(x,y) -n1(z) ≧
0.05, wherein n1(x,y) >
n2(x,y) and n1(z) ≦
n2(z), such that for an incident beam striking a major surface of the stretched multilayered stack at any angle of incidence θ
within a range of angle of incidence, the incident beam having a useful bandwidth, a p-polarized component and an s-polarized component, the beamsplitter exhibits an average reflectivity Rp for the p-polarized component of the incident beam and an average reflectivity Rs for the s-polarized component of the incident beam, wherein Rp and Rs differ by less than 25%. - View Dependent Claims (27, 28, 29, 30, 31, 32, 33, 34)
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35. A nonpolarizing beamsplitter, comprising a multilayered stack having two major surfaces, the multilayered stack comprising alternating layers of a first material and a second material, wherein each of the layers has an x-direction and a y-direction forming an x-y plane, and a z-direction perpendicular to the x-y plane, wherein the first material layers have an index of refraction in the x-y plane, n1(x,y) and an index of refraction in the z-direction n1(z), wherein the first material layers are uniaxially birefringent such that n1(x,y) -n1(z) =0.05, wherein the second material layers have an index of refraction in the x-y plane, n2(x,y), and an index of refraction in the z-direction, n2(z), wherein n1(x,y) >
- n2(x,y), and n1(z) <
n2(z), such that an incident beam of light, striking a major surface of the multilayered stack at any angle of incidence θ
within a range of angles from 0°
to 70°
in air, and having a p-polarized component and an s-polarized component, exhibits a reflectivity Rp for the p-polarized component of the incident beam and a reflectivity Rs for the s-polarized component of the incident beam at each interface of the first and the second material which differ by less than 25% for each angle of incidence within the range.
- n2(x,y), and n1(z) <
Specification