Polarizer and optical apparatus
This polarizer is a polarizer having a wire grid structure that includes a transparent substrate, a dielectric film which extends across one surface of the transparent substrate and has a lower refractive index than the transparent substrate, and a plurality of projections which extend in a first direction on top of the dielectric film and are arrayed periodically at a pitch that is shorter than the wavelength of the light in the used light region, wherein the transparent substrate has a thermal conductivity of at least 10 W/m·K but not more than 40 W/m·K, the plurality of projections each have, in order from the side closer to the dielectric film, a first dielectric layer, a reflective layer and a functional layer, the reflective layer contains a metal or a metal compound, and the functional layer is formed from a material different from the reflective layer.
1. A polarizer comprising:
a transparent substrate,
a dielectric film which extends over a surface of the transparent substrate and has a lower refractive index than the transparent substrate, and
a plurality of projections which extend in a first direction on top of the dielectric film and are arrayed periodically at a pitch that is shorter than a wavelength of light in a used light region, wherein
the transparent substrate has a thermal conductivity of at least 10 W/m·K but not more than 40 W/m·K,
the plurality of projections each have, in order from a side closer to the dielectric film, a first dielectric layer, a reflective layer and a functional layer,
the reflective layer comprises a metal or a metal compound,
the functional layer is formed from a material different from the reflective layer,
a thickness of the first dielectric layer is at least 20% but not more than 80% of a thickness of the dielectric film, and
a refractive index of the transparent substrate is deemed n s , a refractive index of the dielectric film is deemed n a , and a refractive index of an in-plane region including the first dielectric layer is deemed n 1 , then a relationship 1<n 1 <n a <n s is satisfied.
2. The polarizer according to claim 1 , wherein the functional layer has, in order from a side closer to the transparent substrate, a second dielectric layer, an absorption layer comprising an absorptive material, and a third dielectric layer.
3. The polarizer according to claim 1 , wherein the functional layer has a mixed layer comprising a mixture of a dielectric material and an absorptive material.
4. The polarizer according to claim 1 , wherein a refractive index of the transparent substrate is at least 1.70 but not more than 1.80.
5. The polarizer according to claim 1 , wherein a cross-section obtained by cutting the first dielectric layer through a section orthogonal to the first direction is rectangular, trapezoidal, or pseudo-trapezoidal with curved sides.
6. The polarizer according to claim 5 , wherein in the cross-section, an angle between a side surface and a bottom surface of the first dielectric layer is at least 20° but not more than 90°.
7. The polarizer according to claim 1 , wherein a thickness of the first dielectric layer is at least 10 nm but not more than 100 nm.
8. The polarizer according to claim 1 , wherein a thickness of the dielectric film is at least 40 nm but not more than 120 nm.
9. The polarizer according to claim 1 , wherein a transmission axis reflectance in a wavelength region from at least 430 nm to not more than 680 nm is 1% or less.
10. An optical apparatus comprising the polarizer according to claim 1 .
11. The polarizer according to claim 1 ,
wherein an internal angle θ between a bottom surface of the first dielectric layer and each side surface of the first dielectric layer is 70° to 80°, and
a transmission axis reflectance in a wavelength region from at least 430 nm to not more than 680 nm is 1% or less.