Does a material change the direction of polarization of light?

In summary: What do you mean by "nature"? I suppose it might tell you a bit about how conductive the material is that the EM is getting reflected off of, but there are so many other things that affect the reflection (like size of the...
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Shadi Abdelhadi
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The polarization referes to the direction of the electric field of a light wave which is to be one direction. The unpolarized light interacts with a material in various ways such as reflection, scattering, refraction. and each of which can transform an unpolarized light into a vertically or horizontally polarized light with respect to the plane of the material. In co-polarization SAR images, there are certain features that appear VV vertically sent and vertically received images , and other features only appear in HH horizontally sent horizontally received images. Then why the need for cross-polarization systems VH, HV. How can a radar antenna that is adjusted to a vertical polarization axis receive hortizontally polarized reflected echos? How is it even possible for the direction of the electric field to change 45 degrees upon interaction with a certain material
 

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Shadi Abdelhadi said:
How is it even possible for the direction of the electric field to change 45 degrees upon interaction with a certain material
Take a simple example with dipole antennas and a simple wire reflector. Transmit a vertically polarized signal with the vertical dipole, and that EM wave encounters a wire reflector that is set at 45 degrees. That EM excites a current in the wire (less than if it were vertically oriented, but still a substantial current), which then causes EM radiation at that 45 degree angle. So yes, vertically polarized EM radiation can get rotated as part of being reflected -- it happens all the time.
 
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  • #3
Shadi Abdelhadi said:
Summary:: The cross-polarization principle of SAR imaging says there's an option to transmit vertically polarized echos and receive horizontally polarized echos or vice versa. Is it possible that vertically polarized light can be reflected horizontally polarized

Interesting question- I am familiar with this kind of analysis in radar/millimeter wave applications, but I think it's possible in general by considering s- and p-polarization states, which is set by the orientation of a surface relative to the direction of propagation. I tried to envision a Brewster window doing this but couldn't quite figure it out.

More generally, if the surface is rough and depolarizes incident light (or if a bulk media is turbid and scatters light), cross-polarization measurements can quantify how much depolarization is happening. The references I found online point to wind speed measurements as another application.
 
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So if the surface is non-uniform, may depolarization occur? Or may the electric field of the incident light beam rotate 45 degrees upon interaction with the material based on its degree of roughness. Also, through the cross-polarization state, can we indicate the roughness width, hight or the lay direction relative to the polarization direction of the reflected beam. I appreciate your interest.
 
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Shadi Abdelhadi said:
So if the surface is non-uniform, may depolarization occur? Or may the electric field of the incident light beam rotate 45 degrees upon interaction with the material based on its degree of roughness. Also, through the cross-polarization state, can we indicate the roughness width, hight or the lay direction relative to the polarization direction of the reflected beam. I appreciate your interest.
There's an enormous amount of literature on this subject going back to the 1960's:

@article{bahar1987review,
title={Review of the full wave solutions for rough surface scattering and depolarization: Comparisons with geometric and physical optics, perturbation, and two-scale hybrid solutions},
author={Bahar, Ezekiel},
journal={Journal of Geophysical Research: Oceans},
volume={92},
number={C5},
pages={5209--5224},
year={1987},
publisher={Wiley Online Library}
}

@article{khenchaf2001bistatic,
title={Bistatic scattering and depolarization by randomly rough surfaces: application to the natural rough surfaces in X-band},
author={Khenchaf, Ali},
journal={Waves in random media},
volume={11},
number={2},
pages={61--90},
year={2001},
publisher={Taylor \& Francis}
}

@article{campbell1996lava,
title={Lava flow surface roughness and depolarized radar scattering},
author={Campbell, Bruce A and Shepard, Michael K},
journal={Journal of Geophysical Research: Planets},
volume={101},
number={E8},
pages={18941--18951},
year={1996},
publisher={Wiley Online Library}
}

etc etc etc
 
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  • #6
berkeman said:
Take a simple example with dipole antennas and a simple wire reflector. Transmit a vertically polarized signal with the vertical dipole, and that EM wave encounters a wire reflector that is set at 45 degrees. That EM excites a current in the wire (less than if it were vertically oriented, but still a substantial current), which then causes EM radiation at that 45 degree angle. So yes, vertically polarized EM radiation can get rotated as part of being reflected -- it happens all the time.

Does the rotation of the electric field polarization give any clues about the nature of the reflecting material?
 
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Shadi Abdelhadi said:
Does the rotation of the electric field polarization give any clues about the nature of the reflecting material?
What do you mean by "nature"? I suppose it might tell you a bit about how conductive the material is that the EM is getting reflected off of, but there are so many other things that affect the reflection (like size of the reflector, shape, roughness, etc.) that it would be hard to single any particular thing out.
 
  • #8
Well, to be more specific, i study the Radar microwaves and their interactions with rocks, if the type of rock is known by other means, what should the reflected signals, having a different polarization state from the incident signal, indicate about the substrate in terms of roughness or geometry?
 

FAQ: Does a material change the direction of polarization of light?

1. What is polarization of light?

Polarization of light refers to the direction in which the electric field of a light wave oscillates. Light waves can be either linearly polarized, where the electric field oscillates in a single plane, or circularly polarized, where the electric field rotates in a circular motion.

2. How does a material change the direction of polarization of light?

Materials can change the direction of polarization of light through a phenomenon called birefringence. Birefringent materials have different refractive indices for light polarized in different directions, causing the light to split into two perpendicular components with different velocities. This results in a change in the direction of polarization of the light.

3. What types of materials can change the direction of polarization of light?

Materials that exhibit birefringence, such as crystals, can change the direction of polarization of light. These materials have a highly ordered molecular structure that causes light to split into two components with different refractive indices.

4. How does the angle of incidence affect the direction of polarization of light?

The angle of incidence, or the angle at which light enters a material, can affect the direction of polarization of light. In birefringent materials, the angle of incidence can determine the relative intensities of the two polarized components, resulting in a change in the direction of polarization.

5. Can the direction of polarization of light be changed back?

Yes, the direction of polarization of light can be changed back by passing it through another birefringent material with a different orientation. This process, known as polarization rotation, is commonly used in devices such as polarizing filters and liquid crystal displays.

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