High beam quality tapered semiconductor lasers

Free space laser communication becomes one of the most attractive research pot of next generation optical communication technologies due to its advantages of large data transmission amount, high directionality of transmission and high transmission security. The tapered semiconductor lasers are one of the most important optical sources in such systems. In this paper, we introduce the structure design, output characteristics and beam quality of 808 nm tapered semiconductor lasers. The total length of laser cavity is 2.5 mm (tapered single emitters consist of a ridge section with length of 500 μm and a tapered section with length of 2 mm, the tapered angle is 6°). Si/SiO₂ (95% reflectivity) is deposited at the rear facet by using the electronic beam evaporator. The front facet is coated with a single layer of SiON (<; 0.1% reflectivity). The threshold current of the device is 0.75 A. The maximum slope efficiency is 0.46 W/A. The output power of 1.5 W, horizontal divergence of 3.9°, vertical divergence of 38°, M² factor less than 1.9 have been achieved. It shows relative good beam quality.