I have not yet gotten any definite answer. Hope some of you can help me about this question: We know that for the polarisation of the wave: * TE modes (Transverse Electric) no electric field in the direction of propagation. * TM modes (Transverse Magnetic) no magnetic field in the direction of propagation. * TEM modes (Transverse ElectroMagnetic) no electric or magnetic field in the direction of propagation. * Hybrid modes nonzero electric and magnetic fields in the direction of propagation. (from wiki, sorry) So, i call vector k is the wave vector, that means the direction of the wave; we knew that k,E,H always perpendicular each other (k_l_E, E_l_H, H_l_k) (*). It is very clear in the case TEM, but see the case of TE for example, TE means in the direction of k, E=0 (no electric field in the direction of propagation), but, where is H? of course H is not the same in the case TEM (in this case H in the plane _l_k to have H=0 in k direction), ----but if H wants to be perpendicular with k (*), H have to be in the plane which is perpendicular with k ---> become TEM ---> TE is not exist !!!???? How to explane this ? Sorry for my english and thanks.