Optical confinement of envelope wavefunctions in photonic crystal heterostructures

The optical confinement of envelope wavefunctions in photonic crystal heterostructures was studied. Coupled mode theory was used to calculate the states of 2D photonic crystal heterostructures (PCHs) consisting of a core photonic crystal (PC) embedded in a cladding PC. The core consists of larger-size coupled microcavities or waveguides and the cladding comprises smaller size elements. The photonic dispersion of each sub-lattice in the vicinity of the band edge was modeled using the effective propagation constants of the PC elements and the coupling constants between nearest neighbors. The calculated near field patterns of the two highest-order supermodes in a VCSEL-based PCH are presented. Confinement of the envelope functions to the PCH core arises due to the fact that the core modes lie in the forbidden gap of the PCH cladding. The lowest loss (out-of-phase) mode is always confined, whereas the confinement of lower order ones depends on the chosen parameters.