How we can know whether a material is bi-anisotropic or anisotropic

[humFdz]

I would like to distinguish a metamaterial whether it have anisotropic or bianisotropic behavior. Are there a way to do that if you do not know anything about its constitutive parameters?

 

[c_mitra]

You need to formulate the question in practical terms:

1. How much material you have?
2. What is the frequency range you are interested?
3. How much anisotropy is expected (1e-3 or 1e-6 or something else)?
4. Whether the material is crystalline or plastic (this matters because some plastics may become crystalline with time)?
5. You are interested in room temp and normal pressures or under exotic conditions?

Most important is the range of wavelength you want to study.

 

[humFdz]

Thanks for your quick answer.
I am working with metamaterials so I can have several unit cells the dimension of each are 14.4x13.7 mm and I made a prototype consist of 8x8 unit cells. the frequency range is 5-7 GHz. I don't know how much anisotropy could expect. It could be considered as a crystalline material. I would work under room temp.

 

[c_mitra]

As your samples are regular crystalline material, the task is simpler. However, unit cell have a different meaning in connection with crystals (I assume you mean single crystals). You need to deposit gold electrodes (even silver paint will do) on opposite faces and study dielectric absorption. Using a low power microscope try to identify the crystal point group (so that you can label the opposite faces) and select the principal axes. You may need help from some professional crystallographer. What is the instrument you are planning to use to measure dielectric absorption?

 

[c_mitra]

If my memory is right, all crystal structures except the cubic has some asymmetry and hence anisotropy.

 

[humFdz]

thanks a lot again.

Yes, the aim of my prototype is to use it as an absorber. The cell consist of metallization in the top layer dielectric and ground plane. I would like to identify the anisotropy measuring de cross polarization under different angles of incidence, but I am not sure if this could be done.

 

[c_mitra]

I am not sure how to get a polarizer for GHz radiation but you can certainly use microwave tools and techniques to study the anisotropy. In fact, even without a polarizer, you can measure the dielectric absorption and identify the electrical axes and compute the anisotropy tensor. You may not get very high accuracy, but certainly usable values can be obtained using simple techniques.

 

[humFdz]

Could you give me some references where do that?. I cannot find a good explanation where someone carry on several measurements and predict that the prototype is behaving as a bianisotropic or anisotropic material.