CN113534306A

CN113534306A - High extinction ratio broadband line polaroid

Info

Publication number: CN113534306A
Application number: CN202110792954.0A
Authority: CN
Inventors: 郝翔; 何欣; 刘旭
Original assignee: Zhejiang University ZJU
Current assignee: Zhejiang University ZJU
Priority date: 2021-07-14
Filing date: 2021-07-14
Publication date: 2021-10-22
Anticipated expiration: 2041-07-14
Also published as: CN113534306B

Abstract

The invention discloses a high extinction ratio broadband linear polarizer, which adopts double-polished quartz glass as a substrate, wherein a nanostructure is arranged on the substrate and consists of a plurality of nanostructure units arranged in an array manner, the nanostructure units are rectangular metal-nonmetal-metal sandwich nanorods, the distances between the transverse direction nanostructure units and the longitudinal direction nanostructure units are respectively the same, the sizes of all the nanostructure units are the same, and the thicknesses and the materials of two metal layers in each nanostructure unit are the same. The linear polarizer has the maximum extinction ratio of more than 10000 in the visible light range, and the waveband with the extinction ratio of more than 500 is 460-660 nanometers. The linear polaroid improves the transmissivity under TM light, and simultaneously reduces the transmissivity under TE light, so that high extinction ratio is generated, and the minimum transmissivity under TM light is more than 50%.

Description

High extinction ratio broadband line polaroid

Technical Field

The invention belongs to the field of imaging equipment and optical devices, and relates to a high-extinction-ratio broadband linear polarizer based on a metal-nonmetal-metal sandwich nanorod structure and application thereof.

Background

Polarizing plates are widely used in optical systems such as liquid crystal displays, optical measurement, optical communications, and beam splitters, and are indispensable optical devices. Light of a particular polarization direction may be allowed to pass (typically TM light) and the transmission of TE light may be prevented or reduced. In the past, linear polarizers have been made primarily of various organic materials, such as liquid crystals. The liquid crystal must be conductive to produce the polarization effect. Some polarizers are made of structures of nano gratings, but the extinction ratio is limited, and the waveband with the larger extinction ratio is shorter, for example, in a visible light waveband, the waveband with the extinction ratio of more than 500 of few wired polarizers can reach 200 nanometers and more. Generally, a polarizer with an extinction ratio greater than 500 can achieve the polarizing effect. Therefore, it is a trend in the field of optical devices to design a linear polarizer having a wide band with a large extinction ratio.

Disclosure of Invention

In order to solve the problems, the invention provides a linear polarizer based on a metal-nonmetal-metal sandwich nanorod structure.

The purpose of the invention is realized by the following technical scheme: the high extinction ratio broadband linear polaroid adopts double-polished quartz glass as a substrate, a nanostructure is arranged on the substrate and consists of a plurality of nanostructure units arranged in an array manner, the nanostructure units are rectangular metal-nonmetal-metal sandwich nanorods, the distances between the horizontal nanostructure units and the longitudinal adjacent nanostructure units are respectively the same, the sizes of all the nanostructure units are the same, and the thicknesses and the materials of two metal layers in each nanostructure unit are the same.

Further, the thickness of the two metal layers in each nano-structure unit is 30-50 nanometers, and the thickness of the non-metal layer is 30-50 nanometers.

Further, the refractive index n of the non-metal₁N is required to be 1.45-1₁≤1.55。

Further, the metal is aluminum, silver or gold.

Further, the surface of the nano structure is covered with a protective layer, and the refractive index n of the protective layer₂N is required to be 1.38. ltoreq. n₂≤1.42。

Further, the surface of the nano structure is covered with a protective layer, and the thickness of the protective layer is 50-400 nanometers.

Further, the distance between the horizontal adjacent nano-structure units is 90-110 nm, the distance between the vertical adjacent nano-structure units is 720-880 nm, the width of the nanorod is 35-45 nm, and the length is 660-810 nm.

The principle of the linear polarizer of the invention is as follows: generating plasma between metal and nonmetal or between metal and air and generating resonance coupling of a specific wave band; the metal-nonmetal-metal sandwich structure in the vertical direction is based on the fabry-perot principle.

Compared with the prior art, the invention has the following beneficial technical effects: the linear polarizer has the maximum extinction ratio of more than 10000 in the visible light range, and the waveband with the extinction ratio of more than 500 is 460-660 nanometers. The linear polaroid improves the transmissivity under TM light, and simultaneously reduces the transmissivity under TE light, so that high extinction ratio is generated, and the minimum transmissivity under TM light is more than 50%.

Drawings

FIG. 1 is a perspective view of a high extinction ratio broadband linear polarizer provided by an embodiment of the present invention;

FIG. 2 is a top view of the linear polarizer of FIG. 1;

FIG. 3 is a side view of the linear polarizer of FIG. 1;

FIG. 4 is a graph of the spectrum of the linear polarizer of FIG. 1 under TM and TE light;

FIG. 5 is a schematic representation of the extinction ratio of the linear polarizer of FIG. 1;

FIG. 6 is an enlarged view of the extinction ratio of FIG. 5, showing the band range where the extinction ratio is greater than 500.

Detailed Description

For better understanding of the technical solutions of the present application, the following detailed descriptions of the embodiments of the present application are provided with reference to the accompanying drawings.

It should be understood that the embodiments described are only a few embodiments of the present application, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

The terminology used in the embodiments of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in the examples of this application and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

The invention provides a high extinction ratio broadband linear polarizer, which adopts double-polished quartz glass as a substrate, wherein a nanostructure is arranged on the substrate and is formed by a plurality of nanostructure units arranged in an array manner, the nanostructure units are rectangular metal-nonmetal-metal sandwich nanorods, the distances between the transverse direction nanostructure units and the longitudinal direction adjacent nanostructure units are respectively the same, the sizes of all the nanostructure units are the same, and the thicknesses and the materials of two metal layers in each nanostructure unit are the same.

Further, the thickness of the two metal layers in each nano-structure unit is 30-50 nanometers, and the thickness of the non-metal layer is 30-50 nanometers; refractive index n of said non-metal₁N is required to be 1.45-1₁Less than or equal to 1.55; the metal is aluminum, silver or gold.

Further, the surface of the nano structure is covered with a protective layer, and the refractive index n of the protective layer₂N is required to be 1.38. ltoreq. n₂Less than or equal to 1.42, and the thickness of the protective layer is 50-400 nanometers.

As shown in fig. 1 to 3, a specific structure example of the high extinction ratio broadband linear polarizer of the present invention is given. In this example, double-polished quartz glass is used as the substrate on which the nanostructures are provided. The nano structure is composed of a plurality of nano structure units which are arranged in an array manner, the nano structure units are rectangular metal-nonmetal-metal sandwich nanorods, the distances between the horizontal adjacent nano structure units and the longitudinal adjacent nano structure units are respectively the same, the distance between the horizontal adjacent nano structure units is 100 nanometers, and the distance between the longitudinal adjacent nano structure units is 800 nanometers. All the nanostructure units are the same in size, with the width of the nanorods being 40 nm and the length being 730 nm. The thickness and the material of the two metal layers in each nanostructure unit are the same, in this embodiment, the thickness of the two metal layers is 40 nm, the thickness of the nonmetal layer is 40 nm, the metal is aluminum, and the nonmetal is silicon dioxide. The surface of the nano structure is covered with a protective layer, and the protective layer is silicon dioxide with the thickness of 200 nanometers. Fig. 4 is a graph of the spectrum of the linear polarizer for TM and TE light, and it can be seen that the linear polarizer increases the transmittance for TM light while decreasing the transmittance for TE light, thereby resulting in a high extinction ratio, and the minimum transmittance for TM light is greater than 50%. Fig. 5 is a schematic diagram showing the extinction ratio of the linear polarizer of the present example, and fig. 6 is an enlarged diagram showing the extinction ratio of fig. 5, and it can be seen that the linear polarizer of the present example operates in the visible light band, the maximum extinction ratio in the visible light range is greater than 10000, and the band with the extinction ratio greater than 500 is 460 nm to 660 nm.

The above description is only for the purpose of illustrating the preferred embodiments of the one or more embodiments of the present disclosure, and is not intended to limit the scope of the one or more embodiments of the present disclosure, and any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the one or more embodiments of the present disclosure should be included in the scope of the one or more embodiments of the present disclosure.

Claims

1. The high extinction ratio broadband linear polaroid is characterized in that double-polished quartz glass is used as a substrate, a nanostructure is arranged on the substrate and consists of a plurality of nanostructure units arranged in an array manner, the nanostructure units are rectangular metal-nonmetal-metal sandwich nanorods, the distances between the transverse nanostructure units and the longitudinal adjacent nanostructure units are respectively the same, the sizes of all the nanostructure units are the same, and the thicknesses and the materials of two metal layers in each nanostructure unit are the same.

2. The high extinction ratio broadband linear polarizer according to claim 1, wherein the thickness of the two metal layers in each nanostructure element is 30-50 nm, and the thickness of the non-metal layer is 30-50 nm.

3. The high extinction ratio broadband linear polarizer according to claim 1, wherein the refractive index n of the non-metal is greater than the refractive index of the non-metal₁N is required to be 1.45-1₁≤1.55。

4. The high extinction ratio broadband linear polarizer according to claim 1, wherein the metal is aluminum, silver, gold.

5. The polarizer according to claim 1, wherein the surface of the nanostructure is covered with a protective layer, and the refractive index n of the protective layer is larger than the refractive index n of the protective layer₂N is required to be 1.38. ltoreq. n₂≤1.42。

6. The polarizer according to claim 1, wherein the nanostructure surface is covered with a protective layer, and the thickness of the protective layer is 50 nm to 400 nm.

7. The polarizer according to claim 1, wherein the distance between adjacent nanostructure units in the transverse direction is 90-110 nm, the distance between adjacent nanostructure units in the longitudinal direction is 720-880 nm, the width of the nanorod is 35-45 nm, and the length is 660-810 nm.

8. The high extinction ratio broadband linear polarizer according to claim 1, wherein the principle of the linear polarizer is as follows: generating plasma between metal and nonmetal or between metal and air and generating resonance coupling of a specific wave band; the metal-nonmetal-metal sandwich structure in the vertical direction is based on the fabry-perot principle.

9. The linear polarizer of claim 1, wherein the linear polarizer operates in the visible light band, the maximum extinction ratio in the visible light range is greater than 10000, and the wavelength band with the extinction ratio greater than 500 is 460 nm to 660 nm.

10. The high extinction ratio broadband linear polarizer according to claim 1, wherein the linear polarizer increases the transmittance under TM light while decreasing the transmittance under TE light, thereby resulting in a high extinction ratio, and the minimum transmittance under TM light is greater than 50%.