Linear Polarization: Active or Passive Element?

[ProTerran]

Hi, is a linear polarizer acting like an active element that rotates polarization angle or is it just a passive element?

I wonder about this because there is this experiment with three polarizers, where two of them are rotated 90 degree to each other so no light can pass through, and then third polarizer is put between those two with i.e. 45 degrees so that light can pass.

What physical phenomena is behind this?

Best regards.

(Note: English isn't my mother language)

 

[Antiphon]

It is a passive device. It is a classical experiment as well and does not require quantum mechanics to explain how it works.

The polarizer can be made of a fine grid of wires in the vertical direction. When light strikes it, it makes current flow up and down the wires. If the incoming wave is vertically polarized it will be reflected by the wires. If horizontally polarized it will not. At 45 degrees, half the light is reflected and half transmitted *and rotated* to vertical linearly polarized light by the current flow and orientation of the wires.

Edit: you can view this as a decomposition into two waves one of which is passed by the polarizer and one which is not. In this case the polarizer does not rotate the wave but just filters it. Both are mathematically and physically equivalent.

 

[ProTerran]

Thanks for your response.

So does that mean that the current flow induced in "wires" by incident light on the polarizer surface is causing rearranging of the light polarization and absorption/reflection of the light whose polarization angle is lined up with the polarizer "wires"?

 

[Antiphon]

Yes, exactly.