DLL (Diffractive): How to simulate for Grid Wire Polarizer

  • 20 May 2020
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In this post, it’s introduced how to simulate realistic grid wire polarizer with RCWA function that comes with OpticStudio 20.2.

200520-103331-image.png

(Source: https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=5510)

 

Note there are many different types of polarizer

 

Back to Grid Wire Polarizer

In past, the grid wire polarizer was mainly simulated with Jones Matrix or DBEF, which are ideal models.

How to model a Dual Brightness Enhancement Film

How to use the Jones Matrix surface

 

Since OpticStudio 20.2, a new diffractive DLL called “srg_gridwirepolarizer.DLL” for accurately handling this kind of polarizer is added. This DLL is based on RCWA algorithm. More about RCWA can be found in the following article: Simulating diffraction efficiency of surface-relief grating using the RCWA method

To demo how to set up an accurate grid wire polarizer model with this DLL, a sample file is attached in this forum post. In the sample file, it can be seen the system is set up as below.

 

200520-102855-image.png

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Object 1 is a source that will always send one ray in z direction. By looking at Object Property > Sources, it can be seen the source is y-polarized.

200520-102912-image.png

 

Object 2 is a User Defined Object reading the DiffractionGrating.DLL. This object’s first face is diffractive and set with the “srg_gridwirepolarizer_RCWA.dll”. This DLL can simulates binary grating. A grid wire polarizer here is simulated as a binary grating but period much smaller than light wavelength and the material being metal (n = 0.7-7i).

200520-102922-image.png

The shape of the grating can be checked with the tool User Extension > RCWA_visualization.

200520-102931-image.png

By clicking “Draw”, the geometry of the grid wire polarizer can be shown as below.

The meaning of the parameters is explained in the above picture. The grating direction is along the y-axis and can be changed by Rotate Grating parameter.

Again, more information about this tool can be found in the knowledge base article: Simulating diffraction efficiency of surface-relief grating using the RCWA method.

In the sample file, there are 4 Universal Plot draws the energy received by the 4 detectors. In the plots, the incident light’s polarization state is rotated.

It can be seen, at x = 0, Transmit X = 85%, Reflect X = 7%, Transmit Y = 0%, Reflect Y = 0%

And at x = 90, which means ray is incident with exact x polarization:

Transmit X = 0%, Reflect X = 0%, Transmit Y = 0%, Reflect Y = 93%

 


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Userlevel 6
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I guess people who look at this article would also be interested in the following model!

This is only ideal but fast. It also provides the typically pattern when you have two polarizers orthogonally overlapped!

 

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