Threshold gain due to distributed-feedback in two-dimensional triangular- and square-lattice photonic crystal lasers

Numerical simulation of 2D square (SQ)- and triangular (TR)-lattice infinit r-width photonic crystal distributed-feedback (DFB) lasers showed that the threshold gain (g(th)) for the 3rd photonic band was the smallest in the Ga mma -X direction (SQ-lattice), and was next smallest in the Gamma -M direct ion (TR-lattice), but one order of magnitude larger. The g(th) values for t he 3rd photonic bands were qualitatively proportional to the slopes approxi mated for the 3rd bands, but the g(th) values for the 1st bands were indepe ndent of the lattice structure and direction. All the g(th) values for the 1st and 3rd bands decreased to about 1/50 of the original values when the t hickness was increased from 8 to 32 cylinders because of the approaching of the threshold wavelength to the band edge and the longer optical path.