Experimental observation of minigap stripes in periodically corrugated broad photonic wires

Abstract

A multimodal one-dimensional photonic wire subject to a periodic corrugation of the boundary exhibits minigaps among its dispersion branches. For equidistant branches, these minigaps form marked stripes that occupy a substantial fraction of the dispersion diagram and deeply modulate the photon density of states. We experimentally observe these stripes in relatively broad planar photonic wires---$15--30\text{ }\ensuremath{\lambda}/n$ wide---whose lateral confinement is based on two-dimensional photonic-crystal lattices defined in a vertically confining InP heterostructure. The waveguides are tilted at an angle to collect the spontaneous emission of embedded quantum wells channeled into the modes corresponding to the dispersion branches. The minigap stripes manifest themselves as large intensity modulations in the spontaneous emission spectra in TE and TM polarizations. An analogy with the appearance of similar minigap stripes in the recently studied edge-corrugated graphene nanoribbons is pointed out.