Building a polarizer from FR-4?

[yefj]

Hello , I have the theory from the books shown below where we can change the polarization of an incident wave.
suppose we have TEM wave where E field is in X direction.
so if n1=1 (vacuum) and n2=sqrt(4) )=2 FR-4
phi=(1-2)*(2*pi*lambda*0.25)/lambda=pi/2
so by this logic after quarter wavelength in FR-4 ,linear polarized wave will have circular polarization?
https://eceweb1.rutgers.edu/~orfanidi/ewa/ch04.pdf

 

[tech99]

But is FR4 bi-refringent?

 

[yefj]

Hello tech99,the math doesnt take it into account.
we have n1 and n2 and thats it.
Where did i go wrong?
Thanks.

rystalline materials may have different indices of refraction associated with different crystallographic directions. A common situation with mineral crystals is that there are two distinct indices of refraction, and they are called birefringent materials. If the y- and z- directions are equivalent in terms of the crystalline forces, then the x-axis is unique and i

 

[berkeman]

But is FR4 bi-refringent?

I don't think so.

Crystalline materials may have different indices of refraction associated with different crystallographic directions.

FR-4 is not crystalline:

“FR” is an abbreviation for Flame Retardant, and Type “4” indicates woven glass reinforced epoxy resin.

https://www.google.com/url?sa=t&sou...oQFnoECB0QAw&usg=AOvVaw114GYCumgg6VLBkP0hrPS5