Subwavelength plasmon polarization converter

A polarization converter and plasmon technology, applied in instruments, electrical components, optical components, etc., can solve the problems of low efficiency of polarization converters, complicated preparation, narrow bandwidth, etc., and achieve large working bandwidth, high conversion efficiency, simple structure

Inactive Publication Date: 2014-03-19
NANJING UNIV OF TECH
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0004] In order to solve the shortcomings of low efficiency, narrow bandwidth or complicated preparation of the current 90-degree polarization converter, the present invention provides a sub-wavelength polarization converter, which not only has a simple structure, but also has high conversion efficiency and wide operating bandwidth. Big

Method used

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Experimental program
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Effect test

Embodiment 1

[0023] As a first embodiment, the working frequency of the polarization converter is in the optical frequency band. The converter is composed of a gold film / silicon nitride / gold film sandwich structure, and pre-designed microstructures are respectively prepared on the gold film. During the experiment, a 100-nm-thick gold film was coated on both sides of a suspended 50-nm-thick silicon nitride film by magnetron sputtering, and then a focused ion beam (FIB) system was used to coat the gold films on both sides. Subwavelength pinhole arrays were fabricated separately. The period of the prepared small hole array is 600 nanometers, the length of the rectangular small holes is 400 nanometers, and the width is 150 nanometers, and the size of the entire array is 50 micrometers*50 micrometers. In order to align the rectangular holes on both sides into an L-shaped "cross", four through-marks were made with FIB at the four corners of the sample during processing to assist in positioning ...

Embodiment 2

[0028] As a second embodiment, the working frequency of the polarization converter is in the microwave range. Figure 6 (a) and Figure 6 (b) Actual pictures of a single polarizer and a polarization converter processed by water cutting (water jet), respectively. The perforated metal plate is made of aluminum, its thickness is t=1.5 mm, the period of the hole array is d=60 mm, the side length of the rectangular hole is l=40 mm, and the width w=10 mm. The side length of the entire sample is 660 mm, and contains 11*11 rectangular holes in total. The two metal plates of the converter are separated by an air layer, and the small holes form an L-shaped vertical "cross", and the distance between the plates can be adjusted freely. Figure 6 (c) The experimentally measured transmission spectra (circles and squares) of a single polarizer are given. Two transmission peaks were detected in the incident polarization x direction (T xx , square): The main peak is at 3.53GHz, and the seco...

Embodiment 3

[0031] Based on the above results, the present invention further proposes a design method of a "universal" polarization converter. The converter can switch the polarization of the incoming line to any polarization direction, including orthogonal directions prohibited by Malius' law. To achieve this goal, two schemes are proposed here. The first scheme acts as a transition scheme, which uses Figure 6 The polarizer in (a) acts as the input polarizer, while the output polarization direction is controlled by different output polarizers. The output polarizer is still made of metal aluminum plate, engraved with periodic oblique rectangular holes (the angle θ between the long side of the rectangular hole and the horizontal direction can be set according to needs; the corresponding rectangular holes of the incident and outgoing polarizers form ∠-shaped "cross"). as an example, Figure 8 (a) Gives a real picture of the exit polarizer at θ = 30 degrees. Figure 8 (b) shows the exp...

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Abstract

The invention discloses a subwavelength plasmon polarization converter which comprises an incident polarizer and an emission polarizer which are separated by a medium or air layer. Both the incident polarizer and the emission polarizer are made of plasmon materials, small holes with subwavelength dimensions are engraved on the two polarizers, an included angle is formed between each small hole on the incident polarizer and the corresponding small hole on the emission polarizer, and the end points of the above two small holes are in intersection. When the included angle of two small holes is less than 90 degrees, the incident polarizer only allows the coupling entering of one polarized electromagnetic wave, and the emission polarizer only allows the emission of an electromagnetic wave which is orthogonal with the above polarized direction. By using a near field coupling effect between orthogonal rectangular holes, according to the system, the limitation of the Malus law can be broken, and thus the electromagnetic wave generates effective transmission and the polarization direction is rotated for 90 degrees. The converter can be used as a single-direction transmitter, a subwavelength switch and a modulator.

Description

technical field [0001] The invention relates to a sub-wavelength plasmon polarization converter, which is composed of a pair of metal polarizers engraved with sub-wavelength small holes, which can rotate the linear polarization direction of electromagnetic waves by 90 degrees. The converter can also be used as a unidirectional transmitter, subwavelength switch or modulator. Background technique [0002] Traditional polarizers and polarization converters are mainly based on the dichroism, birefringence effect or optical activity of natural materials, which can generate linearly polarized light or change the polarization state of light waves. It is well known that two linear polarizers can be used to generate linearly polarized light and to rotate the polarization direction of the light. However, according to Marius' law, the light transmission efficiency will decrease with the increase of the rotation angle θ of the polarizer. When θ=90°, the light transmission efficiency b...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G02B27/28H01Q15/00
Inventor 黄成平张勇
Owner NANJING UNIV OF TECH
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