Threshold gain and gain-enhancement due to distributed-feedback in two-dimensional photonic-crystal lasers

Abstract

The threshold gain (g th ) of a two-dimensional (2D) photonic crystal distributed-feedback (DFB) laser composed of 8×8 dielectric cylinders was one order of magnitude smaller than that of an 8-pair 1D DFB laser with the identical refractive indexes. In the 2D finite-width photonic crystal laser, g th using the 1st photonic band was smaller than that using the higher photonic band, contrary to the expectation from the flatness of the photonicband structures. This unexpected g th is probably due to the longer optical path caused by the reflection at the side boundary. Moreover, g th using the 1st photonic band was the smallest in the Γ–X direction of the square-lattice photonic crystal. The gain-enhancement using the 1st–3rd photonic bands were 10–30 in the 2D photonic crystal and that using the 3rd band was the largest. The gain-enhancement using the 1st photonic band of the 2D photonic crystal consisting of dielectric cylinders was larger than that of air cylinders.