Polarizing element and method of producing same

1. A polarizing element having a wire grid structure, comprising:

a transparent substrate; and

grid-shaped protrusions that are arranged on the transparent substrate at a smaller pitch than a wavelength of operating band light and that extend in a specific direction, wherein

the grid-shaped protrusions include a reflection layer formed on the transparent substrate,

the reflection layer includes a metal layer and oxide layers that cover side surfaces of the metal layer as viewed in the specific direction and is formed from an oxide of a constituent metal of the metal layer, and

the grid-shaped protrusions have a grid width, the grid width being defined as a width of the grid-shaped protrusions in an arrangement direction thereof, of 35 nm to 45 nm, and that the polarizing element satisfies 28%≤x<48%, where x stands for a proportion of a combined width of the oxide layers to the grid width in the arrangement direction of the grid-shaped protrusions.

2. The polarizing element according to claim 1 , wherein

the grid-shaped protrusions further include a dielectric layer formed on the reflection layer and an absorption layer formed on the dielectric layer.

3. The polarizing element according to claim 1 , wherein

each oxide layer has an increasing degree of oxidation of the constituent metal of the metal layer with increasing proximity to an outermost surface of each oxide layer.

4. A method of producing a polarizing element having a wire grid structure, comprising:

forming a metal layer that is arranged on a transparent substrate at a smaller pitch than a wavelength of operating band light and that extends in a specific direction;

forming a dielectric layer on the metal layer;

forming an absorption layer on the dielectric layer; and

forming oxide layers from an oxide of a constituent metal of the metal layer at side surfaces of the metal layer by oxidizing the metal layer after the absorption layer is formed, wherein

grid-shaped protrusions include the metal layer, the dielectric layer, the absorption layer and the oxide layers, and have a grid width, the grid width being defined as a width of a grid-shaped protrusion in an arrangement direction thereof, of 35 nm to 45 nm, and that the polarizing element satisfies 28%≤x<48%, where x stands for a proportion of a combined width of the oxide layers to the grid width in the arrangement direction of the grid-shaped protrusion.

5. The method of producing a polarizing element according to claim 4 , wherein

the metal layer is oxidized by heat treatment in the forming of the oxide layers.

6. The method of producing a polarizing element according to claim 5 , wherein

each oxide layer has an increasing degree of oxidation of the constituent metal of the metal layer with increasing proximity to an outermost surface of each oxide layer.

7. A method of producing a polarizing element that includes a transparent substrate and grid-shaped protrusions that are arranged on the transparent substrate at a smaller pitch than a wavelength of operating band light and that extend in a specific direction, the grid-shaped protrusions having a grid width, the grid width being defined as a width of the grid-shaped protrusions in an arrangement direction thereof, of 35 nm to 45 nm, and the polarizing element having a transmission characteristic of transmission axis transmittance of 93.5% or more when incident light is green band light having a wavelength λ of 520 nm to 590 nm, the method comprising:

forming a metal layer that is arranged on the transparent substrate at a smaller pitch than a wavelength of operating band light and that extends in the specific direction;

forming a dielectric layer on the metal layer;

forming an absorption layer on the dielectric layer; and

forming oxide layers from an oxide of a constituent metal of the metal layer at side surfaces of the metal layer by oxidizing the metal layer after the absorption layer is formed, wherein the grid-shaped protrusions include the metal layer, the dielectric layer, the absorption layer and the oxide layers, and

the oxide layers being formed with a thickness within a range for which 28%≤x<48%, where x stands for a proportion of a combined width of an oxide layer present at a left side and an oxide layer present at a right side of the metal layer to the grid width in the arrangement direction as viewed in the specific direction, such that the transmission characteristic is satisfied.