[1] Vesalago V G 1968 Sov. Phys. Usp. 10 509

[2] Shelby R A, Smith D R and Schultz S 2001 Science
292 77

[3] Patanjali V P, Wentao T L, Plarenta V and Srinivas S 2003
Nature 426 404

[4] Pendry J B 2003 Opt. Express 11 755

[5] Seddon N and Bearpark T 2003 Science 302 1537

[6] Zhang F L, Zhao Q, Liu Y H, Luo C R and Zhao X P 2004
Chin. Phys. Lett. 21 1330

[7] Zhao X P, Zhao Q, Zhang F L, Zhao W and Liu Y H 2006
Chin. Phys. Lett. 23 99

[8] Zhou J, Zhang L, Tuttle G, Koschny T and Soukoulis C M
2006 Phys. Rev. B 73 041101

[9] Zhou X and Zhao X P 2007 Appl. Phys. Lett. 91
181908

[10] Zhu W R, Zhao X P and Guo J Q 2008 Appl. Phys.
Lett. 92 241116

[11] Yan C C, Cui Y P, Wang Q and Zhuo S C 2008 Chin.
Phys. Lett. 25 482

[12] Zhang S, Fan W J, Panoiu N C, Malloy K J, Osgood R M and
Brueck S R J 2005 Phys. Rev. Lett. 95 137404

[13] Dolling G, Enkrich C, Wegener M, Soukoulis C M and Linden
S 2006 Science 312 892

[14] Liu N, Guo H C, Fu L W, Kaiser S, Schweizer H and Giessen
H 2008 Nature Mater 7 31

[15] Dolling G, Wegener M, Soukoulis C M and Linden S 2007
Opt. Lett. 32 53

[16] Zhang S, Fan W J, Panoiu N C, Malloy K J, Osgood R M and
Brueck S R J 2006 Opt. Express 14 6778

[17] Valentine J, Zhang S, Zentgraf T, Ulin-Avila E, Genov D
A, Bartal G and Zhang X 2008 Nature 455 376

[18] Vesekago V G and Narimanov E E 2006 Nature Mater
5 759

[19] Imhof C and Zengerle R 2009 Appl. Phys. A 94
45

[20] Kafesaki M, Tsiapa I, Katsarakis N, Koschny T, Soukoulis
C M and Economou E N 2007 Phys. Rev. B 75 235114

[21] Smith D R, Schultz S, Markos P and Soukoulis C M 2002
Phys. Rev. B 65 195104

[22] Depine R A and Lakhtakia A 2004 Microwave Opt.
Technol. Lett. 41 315

[23] Dolling G, Enkrich C, Wegener M, Soukoulis C M and Linden
S 2006 Opt. Lett. 31 1800