Permittivity-permeability (s-u)and refractive index (n)diagram. U II. I. e<0,u>0: e>0,4>0: n=E∈L,n<0 n=+√eu∈R,n>0 plasmas(ω<ωpe) isotropic dielectrics metals at optical frequencies right-handed(RH)/ evanescent wave forward-wave propagation 亚. IV. 8<0,u<0: ε>0，u<0: n=-√E平∈R,n<0 n=√Eu∈I,n<0 Veselago's materials ferrites(ω<wpm) left-handed (LH)/ (ferrimagnetic materials) backward-wave propagation evanescent wave