Single transverse-mode and single longitudinal-mode parity-time symmetric Fabry-Perot laser array

Semiconductor laser arrays may provide a viable avenue in scaling up the radiance. However, due to the competition of multiple transverse and longitudinal modes, realizing single-mode laser array has been a long-standing challenge. In this study, we demonstrate electrically pumped single-mode semiconductor Fabry-Pérot (FP) laser arrays by exploiting the emerging non-Hermitian parity-time (PT) symmetry photonic design. The uniform laser array consists of a main array with four-ridge as gain lattice and a coupled loss lattice with the same array structure. We propose a method to control the output mode characteristics of the PT-symmetric laser array and achieve single transverse-mode and single longitudinal-mode operation, with the side-mode suppression ratio (SMSR) improving from a typical value of less than 5 dB to 22.8 dB. The emission power of PT-symmetric laser array is about five times higher than that of the single-ridge laser with the same current density. Our PT-symmetric laser array could find potential applications in integrated optoelectronic devices for optical communication and ranging systems.