Threshold gain and single-mode oscillation of two-dimensional photonic bandgap defect lasers

Defect laser behavior was simulated as a function of various parameters. When the crystal size was increased from 8×8 to 12×12 cylinders, the quality factor of the defect cavity increased from 6×10³ to 5×10⁶ while the threshold gain decreased by two orders of magnitude, It was predicted that a triangular-lattice photonic defect laser would be polarized in the Γ-M direction. The defect laser studied usually showed multi-mode oscillation with a large defect radius, where the threshold gain was small. When the refractive indices of the cylinders and the defect, surrounded by air, were both 3.5, single-mode oscillation and a small threshold gain (4 cm^-1) were, nevertheless, achieved at suitable device parameters that made the side-mode suppression ratio sufficiently large at 10³. A single-mode oscillation and a small threshold gain (less than 20 cm(^-1)) were also predicted over the entire defect radius range when the defect refractive index was decreased from 3.5 to 1.5