Mode engineering of semiconductor lasers with vertical periodic layered structures

High-power and low-divergence semiconductor lasers are useful in light detection and ranging, as well as material processing and so on. In this paper, an efficient approach is presented to explain the physics of mode selection in semiconductor lasers with vertical periodic layers for high power and low vertical beam divergence. The transmission matrix method is used to obtain the allowed band and forbidden band of the vertical periodic layered structure, and the band diagram of the layered structure of the semiconductor laser. The fundamental mode of the layered structure of the semiconductor laser lies in the forbidden band of the vertical periodic layered structure. Tapered lasers based on the designed layered structure are fabricated and can achieve an output power of 2.45 W. The measured vertical divergence angle of the tapered laser is below 10 degrees, consistent well with the calculated result of 9.5 degrees.