Controlling vertical optical confinement in two-dimensional surface-emitting photonic-crystal lasers by shape of air holes.

We use the finite-difference time domain method to calculate the vertical optical confinement, which corresponds to the quality factor in the vertical direction, of two-dimensional photonic-crystal (PC) lasers as a function of the asymmetry of the shape of the air holes that form the PC. The vertical optical confinement for triangular air holes, which give the highest output power measured thus far, is decreased by two thirds when V-shaped air holes are used. In contrast, the vertical optical confinement becomes infinite for rhomboid air holes. The vertical optical confinement decreases when the air holes are deformed such that areas of opposing electric fields exist in regions of the PC with different dielectric constants. In this way, the vertical optical confinement can be controlled by changing the shape of the air holes.