Photonic realization of topologically protected bound states in   domain-wall waveguide arrays
  We present an analytical theory of topologically protected photonic states for the two-dimensional Maxwell equations for a class of continuous periodic dielectric structures, modulated by a domain wall. We further numerically confirm the applicability of this theory for three-dimensional structures. 
James P. Lee-Thorp, Iva Vuki\'cevi\'c, Xinan Xu, Jinghui Yang, Charles   L. Fefferman, Chee Wei Wong, and Michael I. Weinstein
physics.optics cond-mat.mes-hall math-ph math.AP math.MP