Nonlinear Tamm states and surface effects in periodic photonic structures

We present a brief overview of the basic concepts and important experimental observations of the effect of light localization near the surfaces of truncated periodic photonic structures. In particular, we discuss the formation of nonlinear localized modes and discrete surface solitons near the edges of nonlinear optical waveguide arrays and two-dimensional photonic lattices. We draw an analogy between the nonlineir surface optical modes and the surface Tamm states kown in the electronic theory. We discuss the crossover between discrete solitons in the array and surface solitons at the edge of the array by analyzing the families of even and odd nonlinear localized modes located at finite distances from the edge of a waveguide array. We discuss various generalization of this concept including surface solitons in chirped lattices, multi-gap vector surface solitons, polychromatic surface states generated by a supercontinuum source, surface modes in two-dimensional photonic lattices, and spatiotemporal surface solitons. Finally, we discuss briefly several other related concepts including the enhanced beaming of light from subwavelength waveguides in photonic crystals. A figure is presented. Finite-difference time-domain simulations of the field intensity from the beaming modeling with (a) illustrating the full angle diffused output from the sub-wavelength waveguide exit when the surface structure is simply terminated in a row of cylinders equal in radius to those of the bulk pholonic crystal, and (b) illustrating the highly collimated beam emitted from the waveguide having been strongly fashioned by radiative surface states.