Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Is Poincaire Sphere inverted if the direction of propogation of TEM wave is reversed?

  1. Jun 13, 2010 #1
    My doubt arises because I couldn't understand how a Poincaire Sphere gives us info about direction of propagation of wave. Now as we know Poincaire sphere is a neat way of showing the polarization state of an TEM wave. Now ,let me give an example to illustrate my doubt : -

    Let us take a uniform plane TEM wave travelling in +z direction which is composed of two linearly polarised TEM waves , one whose electric field lies in X direction , the other whose electric field lies in Y direction . Let us take the case of circular polarisation
    so we take ,

    Ex = E0 cos([tex]\omega[/tex] t - [tex]\beta[/tex] z) ax
    Ey = E0 cos([tex]\omega[/tex] t - [tex]\beta[/tex] z + [tex]\pi[/tex]\2) ay

    Now the resultant TEM wave has the Electric field vector left handed circularly polarised .
    On the Poincaire Sphere this will be given by the north pole point.



    Suppose we had same wave but travelling in -ve z direction.
    Ex = E0 cos([tex]\omega[/tex] t + [tex]\beta[/tex] z) ax
    Ey = E0 cos([tex]\omega[/tex] t + [tex]\beta[/tex] z + [tex]\pi[/tex]\2) ay
    So the wave should be right handed circularly polarised(I hope I am right here ) . Now as far as I know , while plotting the polarisation state on the Poincaire sphere we simply take the Phase difference between the two waves and the ratio of their magnitudes into consideration .So according to me , this wave will also be plotted on the north pole point.

    Isn't this a discrepancy (maybe of my understanding) that a right handed circular polarised wave is getting plotted to north pole. So do we invert the Poincaire sphere if we reverse direction of propagation of wave?

    My doubt basically boils down to this - while plotting Polarisation state of a TEM wave on a Poincaire sphere , how is the direction of propagation of the TEM wave taken into account ?
     
  2. jcsd
  3. Jun 14, 2010 #2
    Re: Is Poincaire Sphere inverted if the direction of propogation of TEM wave is rever

    please help in solving my doubt! I hope I was clear in stating the doubt!
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook