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

Defect laser behavior was simulated as a function of various parameters. Wh en the crystal size was increased from 8 x 8 to 12 x 12 cylinders, the qual ity factor of the defect cavity increased from 6 X 10(3) to 5 x 10(5) 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 G amma -M direction. The defect laser studied usually showed multi-mode oscil lation 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 oscil lation 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 d ecreased from 3.5 to 1.5.