Tunable transmission and bistability in left-handed bandgap structures
  We study the defect-induced nonlinear transmission of a periodic structure created by alternating slabs of two materials with positive and negative refractive index. We demonstrate bistable switching and tunable nonlinear transmission in a novel type of bandgap that corresponds to the vanishing average refractive index, and compare the observed effects for two types of the bandgaps. 
Michael W. Feise, Ilya V. Shadrivov, Yuri S. Kivshar