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

 

[yefj]

Hello n1 and n2 are not two different mediums as shown below but one medium ?
In the mathematical part shown below they didnt say in what direction we have n1 and in what direction n2.If its only one medium how can i know the directions in which the EM wave experienced n1 and n2?
Thanks.

 

[berkeman]

Hello n1 and n2 are not two different mediums as shown below but one medium ?
In the mathematical part shown below they didnt say in what direction we have n1 and in what direction n2

Yes they did...

So presumably the EM wave is propagating in the z direction. When you have a material like that, you have birefringence:

https://en.wikipedia.org/wiki/Birefringence

That is different from when you just have a slab of FR-4 (which is not birefringent) that an EM wave encounters and passes through.

BTW, you should have given a link to the source of your screenshot in your first post, or at least said what textbook it was out of. Please take care to provide attribution for quotes and screenshots of copyrighted work in the future. Thanks.

 

[yefj]

Hello,As you can see below I did post a link to the original book webpage in the first post as shown in the photo.
Is it ok?
Thanks.

 

[berkeman]

Yes, I see that now. Sorry that I missed it!