Embedded wire grid polarizer with high reflectivity on both sides
A wire grid polarizer (WGP) 10 can include wires 15 sandwiched between a first pair of thin-film layers 21 (with a first transparent layer 11 and a second transparent layer 12 ) and a second pair of thin-film layers 22 (with a third transparent layer 13 and a fourth transparent layer 14 ). An index of refraction of each outer transparent layer 11 and 14 can be greater than an index of refraction of the adjacent inner transparent layer 12 and 13 , respectively. Material composition of the outer transparent layers 11 and 14 can be the same and material composition of the adjacent inner transparent layers 12 and 13 can be the same. There can be high reflection of one polarization (e.g. Rs1>93% and Rs2>93%) for light incident on either side of the WGP. The wires 15 can be embedded for protection.
1. A wire grid polarizer (WGP) comprising:
a transparent substrate having a first side, and a second side opposite of the first side;
an array of wires located over the first side of the transparent substrate with channels between adjacent wires;
a first pair of thin-film layers: located between the array of wires and the transparent substrate; being continuous and spanning the channels; and including a first transparent layer located closer to the transparent substrate and a second transparent layer located closer to the array of wires;
a second pair of thin-film layers: located at an opposite side of the array of wires from the transparent substrate; being continuous and spanning the channels; and including a third transparent layer located closer to the array of wires and a fourth transparent layer located farther from the array of wires; and
for a wavelength range of at least 100 nm in a visible spectrum of light: an index of refraction of the first transparent layer (n1) is greater than an index of refraction of the second transparent layer (n2); and an index of refraction of the fourth transparent layer (n4) is greater than an index of refraction of the third transparent layer (n3).
2. The WGP of claim 1 , further comprising:
a third pair of thin-film layers: located between the first pair of thin-film layers and the transparent substrate; being continuous and spanning the channels; and including a fifth transparent layer and a sixth transparent layer with the fifth transparent layer located closer to the transparent substrate than the sixth transparent layer;
a fourth pair of thin-film layers: located at an opposite side of the array of wires from the transparent substrate and farther from the array of wires than the second pair of thin-film layers; being continuous and spanning the channels; and including a seventh transparent layer and an eighth transparent layer with the seventh transparent layer located closer to the array of wires than the eighth transparent layer; and
for the wavelength range of at least 100 nm in the visible spectrum of light: an index of refraction of the fifth transparent layer is greater than an index of refraction of the sixth transparent layer; and an index of refraction of the eighth transparent layer is greater than an index of refraction of the seventh transparent layer.
3. The WGP of claim 1 , wherein for the wavelength range of at least 100 nm in the visible spectrum of light: n1−n2>0.5 and n4−n3>0.5.
4. The WGP of claim 1 , wherein for the wavelength range of at least 100 nm in the visible spectrum of light: n1>2.0, n4>2.0, n2<1.55, and n3<1.55.
5. The WGP of claim 1 , wherein:
a material composition of the first transparent layer is the same as a material composition of the fourth transparent layer; and
a material composition of the second transparent layer is the same as a material composition of the third transparent layer, but different from the material composition of the first transparent layer and the fourth transparent layer.
6. The WGP of claim 1 , wherein for the wavelength range of at least 100 nm in the visible spectrum of light, Rs1>93% and Rs2>93%, where: Rs1 is a percent reflection of s-polarized light from a first side of the WGP; Rs2 is a percent reflection of s-polarized light from a second side of the WGP; s-polarized light is a predominantly reflected polarization of incident light; the first side of the WGP is a side of the WGP on which the array of wires is located; and the second side of the WGP is opposite of the first side of the WGP and is a side of the WGP on which the transparent substrate is located.
7. The WGP of claim 1 , further comprising a pair of prisms, the WGP being sandwiched between the pair of prisms, forming a cube polarizing beam splitter (cube PBS).