Surface states in photonic crystals

Propagation of surface electromagnetic waves along photonic crystal (PC) boundaries is examined. It is shown that in a number of cases these waves are backward. The nature of the surface electromagnetic states, localized at the PC boundary, is discussed; these states transfer no energy along the boundary (their tangential wave number is zero). An analogy with the well-known Tamm and Shockley surface states in solid state physics is drawn. It is shown that in the case of PC both types of states can be considered as the Tamm ones. Experimental results on the observation of the surface states are presented. A system using an external magnetic field to control a surface state is considered.