What happens to waves with different polarizations in a wire grid polarizer?

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Discussion Overview

The discussion centers on the behavior of electromagnetic waves with different polarizations as they interact with a wire grid polarizer. Participants explore the absorption and transmission of waves based on their polarization relative to the orientation of the wires, considering both theoretical and practical implications.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant suggests that waves polarized parallel to the wires are absorbed, but questions arise about the empty spaces between the wires allowing some of these waves to pass through.
  • Another participant agrees that some energy from parallel-polarized waves can pass through the gaps, noting that the amount is proportional to the ratio of wire spacing to wavelength.
  • It is proposed that for sufficiently small wire spacing compared to the wavelength, only a small percentage of parallel-polarized energy will pass, while most will be reflected.
  • Conversely, the percentage of energy from perpendicular-polarized waves that gets reflected is also discussed, with a similar proportional relationship to the width of the wires.
  • A later reply challenges the idea that parallel-polarized waves are absorbed, asserting that they are reflected instead, and critiques the clarity of the original source material.

Areas of Agreement / Disagreement

Participants express differing views on whether parallel-polarized waves are absorbed or reflected, indicating a lack of consensus on this point. There is also disagreement regarding the interpretation of the source material referenced.

Contextual Notes

Participants mention specific ratios and conditions under which energy is transmitted or reflected, but these depend on assumptions about wire dimensions and wave properties that are not fully detailed in the discussion.

Pushoam
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It is said that the wave whose polarization is parallel to the wire, gets absorbed by the wire.
But, there is empty space between the wires. So, that part of the above - said wave which passes through the empty space will not get absorbed by the wire. So, the transmitted wave must have the wave whose polarization is parallel to the wire.

On the other hand, some part (maybe small) of all of the wave with polarization perpendicular to the wire should get absorbed by the wires.
So, the resultant transmitted wave should have the wave with both kinds of polarization.

The books which I have come across leave the above-mentioned ideas.
Could anyone please clarify it?
 

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You are right that some energy from waves who have E-field parallel to the wires will pass through the gaps. But if we do the math we can prove that the energy that will pass is proportional to the ratio ##\frac{a}{\lambda}## where ##a## is the spacing between the parallel wires and ##\lambda## the wavelength of the waves. So if we arrange for ##a## to be sufficiently small compared to ##\lambda## only a small percentage of energy will pass and the rest will be reflected.

Also the percentage of the energy from waves who have E-field perpendicular to the wire that gets reflected is proportional to ##\frac{b}{\lambda}## where ##b## the width(the vertical dimension) of the parallel wires. So if ##b## is small in comparison to ##\lambda## very small percentage of this energy will be reflected and the rest will pass.
 
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Thank you.
 
Pushoam said:
the wave whose polarization is parallel to the wire, gets absorbed by the wire
It's reflected and not absorbed. To be absorbed, you would need resistance wire of just the correct resistance value.
There is also a nonsense statement in the attached passage which says that "the electricity trans cannot move very far across the width of the wire". At a mean speed of a mm per second (drift velocity of electrons in a metal) and, assuming we have a classical motion for the electrons, how far in either direction would the electrons go in the period of oscillation of the RF wave? In fact, the whole passage is pretty nonsensical and would be better ignored. I wonder what surprises the other 32 pages have for the reader. Treat it all with care and stick to a proper textbook.
 
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