changing polarisation through a change in medium

[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

 

[FvM]

The linked textbook excerpt is discussing anisotropic media which is necessary to achieve intended polarisation change. FR4 isn't anisotropic.