Inorganic polarizing plate having trapezoid shaped metal layers and production method thereof

1. An inorganic polarizing plate, comprising:

a substrate that is transparent to light in a wavelength range for use;

a plurality of linear metal layers;

a plurality of linear dielectric layers; and

a plurality of linear light-absorbing layers having a light absorbing function, where the substrate, the linear metal layers, the linear dielectric layers, and the linear light-absorbing layers are provided in this order,

wherein the linear metal layers are aligned being apart from each other on the substrate at a pitch shorter than wavelengths of the light,

wherein each linear dielectric layer of the linear dielectric layers is provided on each linear metal layer of the linear metal layers,

wherein each linear light-absorbing layer of the linear light-absorbing layers is provided on each linear dielectric layer of the linear dielectric layers,

wherein a cross-sectional shape of the linear metal layer cut in a direction orthogonally crossing a longitudinal direction of the linear metal layer is a trapezoid with a bottom base being at a side of the substrate, and an upper base being at a side of the linear dielectric layer, where a length of the bottom base is longer than a length of the upper base,

wherein a difference between the length of the bottom base and the length of the upper base [(the length of the bottom base)−(the length of the upper base)] is 1.0 nm to 12.0 nm in the cross-sectional shape of the linear metal layer,

wherein a material of the linear metal layer is aluminum,

wherein a material of the linear dielectric layer is SiO 2 , and

wherein a material of the linear light-absorbing layer is Si, or silicide.

2. The inorganic polarizing plate according to claim 1 , wherein an average thickness of the linear metal layer is 20 nm to 400 nm.

3. The inorganic polarizing plate according to claim 1 , wherein the silicide is silicide containing Fe in an amount of 10 atm % or less.

4. The inorganic polarizing plate according to claim 1 , wherein the silicide is silicide containing Ta in an amount of 40 atm % or less.

5. The inorganic polarizing plate according to claim 1 , wherein a material of the substrate is glass, crystal, or sapphire.

6. A production method of the inorganic polarizing plate according to claim 1 , comprising:

etching a metal layer formed on the substrate using etching gas containing N 2 .

7. The production method according to claim 6 , wherein the etching gas contains Cl 2 and BCl 3 .