Transverse Photonic Crystal Mode Engineering for Broad-Area Semiconductor Lasers With Narrow-Divergence Angles

Broad-area semiconductor lasers, coupled with asymmetric transverse photonic crystals (TPCs), are designed by the effective index method and the transfer matrix method. Due to the propagation constant of the fundamental mode lying in the forbidden band of the TPCs, but those of the high-order modes lying in the allowed band of the TPCs, the fundamental mode is mainly concentrated in the active ridge waveguide, while all the high-order modes extend into the lossy TPCs on both sides of the active ridge waveguide. Therefore, the fundamental mode possesses larger optical confinement factor than those of the high-order modes, and reaches the lasing threshold more easily, which is demonstrated by the single-lobe horizontal far-field pattern of the TPC broad-area laser under an injection current of 0.3 A near the threshold. The proposed TPC broad-area laser provides a new strategy of designing broad-area semiconductor lasers with narrow divergence angles