Conditions of single guided mode in two-dimensional triangular photonic crystal slab waveguides

Photonic band structure analyses are applied to study the effect of slab thickness in two-dimensional photonic crystal slab waveguides. For transverse electric-like modes of a triangular lattice of air holes, the band gap of the asymmetric photonic crystal slab with a drilled low-index cladding do not differ significantly from that of the photonic crystal suspended in air over a wide range of slab thickness. The condition of single guided mode operation is also studied and it is found that the single mode cutoff thickness changes only by a small amount as an air-hole filling ratio varies once the center of the band gap is fixed.