Polarizing plate, method of manufacturing the same, and optical apparatus

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

a transparent substrate; and

grid-shaped protrusions that are arranged on the transparent substrate at a pitch shorter than a wavelength of light in a use band and extend in a predetermined direction,

wherein the grid-shaped protrusion includes, in order from the transparent substrate side, a pedestal, a reflection layer, a dielectric layer, and an absorption layer, and

the pedestal has a trapezoidal shape when viewed from the predetermined direction.

2. The polarizing plate according to claim 1 , wherein a minimum width of the pedestal is equal to or larger than a width of the reflection layer.

3. The polarizing plate according to claim 1 , wherein the pedestal is configured with an Si oxide that is transparent to the wavelength of the light in the use band.

4. The polarizing plate according to claim 1 , wherein a grid tip formed at a tip of the grid-shaped protrusion has a tapered shape where a side face is inclined in such a direction that a width thereof is decreased toward a tip side when viewed from the predetermined direction.

5. The polarizing plate according to claim 4 , wherein the grid tip is configured with the dielectric layer and the absorption layer,

a maximum width of the grid tip is 35 to 45 nm, and

a width of the reflection layer is 52 to 72% of the maximum width of the grid tip.

6. The polarizing plate according to claim 4 , wherein, when an inclination angle of the side face of the grid tip with respect to the transparent substrate is denoted by θ,

a height of the grid tip when viewed from the predetermined direction is denoted by a, a maximum width of the grid tip is denoted by b, and θ 0 =arctan(2a/b),

2/3≤a/b≤8/7 is satisfied, and θ 0 ≤θ<90° is satisfied, and

the inclination angle θ is selected from an angle range in which reflectance of light with a predetermined wavelength in a visible light region in an absorption-axis direction is 10% or less.

7. The polarizing plate according to claim 4 , wherein an inclination angle θ is defined as an inclination angle of a tangent line of the side face of the grid tip at a center position in a height direction of the grid tip when viewed from the predetermined direction, and an angle range thereof is θ≤80°.

8. The polarizing plate according to claim 1 , wherein the transparent substrate is transparent to the wavelength of the light in the use band and is configured with glass, quartz or sapphire.

9. The polarizing plate according to claim 1 , wherein the reflection layer is configured with aluminum or an aluminum alloy.

10. The polarizing plate according to claim 1 , wherein the dielectric layer is configured with an Si oxide.

11. The polarizing plate according to claim 1 , wherein the absorption layer is configured to include Fe or Ta and to include Si.

12. The polarizing plate according to claim 1 , wherein a surface of the polarizing plate on which light is incident is covered with a protective film made of a dielectric material.

13. The polarizing plate according to claim 1 , wherein a surface of the polarizing plate on which light is incident is covered with an organic water-repellent film.

14. An optical apparatus comprising the polarizing plate according to claim 1 .

15. A method of manufacturing a polarizing plate having a wire grid structure, the method comprising:

an underlying layer forming step of forming an underlying layer on a transparent substrate;

a reflection layer forming step of forming a reflection layer on the underlying layer;

a dielectric layer forming step of forming a dielectric layer on the reflection layer;

an absorption layer forming step of forming an absorption layer on the dielectric layer; and

an etching step of selectively etching a formed stack to form grid-shaped protrusions that are arranged on the transparent substrate at a pitch shorter than a wavelength of light in a use band,

wherein, in the etching step, the underlying layer is etched to form a pedestal having a trapezoidal shape when viewed from an extending direction of the grid-shaped protrusions.