Asymmetric design of photonic crystal surface-emitting lasers with low-threshold characteristics.

We present AlGaAs-InGaAs multiquantum wells photonic crystal surface-emitting lasers by using the transfer matrix method and coupled wave method to achieve a low-threshold operation. The extremely low-threshold gain is achieved by adopting an asymmetric cladding layer design to enhance both of the vertical optical confinement factors for the quantum wells and photonic crystal (PC). By modifying the composition of the AlGaAs layer to raise the refractive index in the p-type cladding, optical field distribution will obviously be shifted to the p side. Hence, it results in a significant coupling enhancement between the optical mode profile and the PC layer. The optimized value of the vertically optical confinement factor of the PC layer is 13.94%, and the corresponding threshold gain can be as low as 19.45 cm(-1).