[3] Shelby R A,Smith D R,Schultz S.Experimental verification of a negative index of refraction[J].Science,April,2001,292:77-79.
[4] Smith D R,Kroll N.Negative refractive index in left handed materials[J].Physical Review Letters,2000,85:2933-2936.
[5] Vahidpour M,Shahabadi M.Existence of complex modes in gratings composed of left-handed materials[J].Antennas and Propagation Society International Symposium,IEEE,2005,3A:241-244.