A comprehensive design optimization of 1.55-#m high power InGaAsP/InP board area lasers is performed aiming at increasing the internal quantum efficiency （ηi） while maintaining the low internal loss （αi） of the device, thereby achieving high power operation. Four different waveguide structures of broad area lasers were fabricated and characterized in depth. Through theoretical analysis and experiment verifications, we show that laser structures with stepped waveguide and thin upper separate confinement layer will result in high αi and overall slope efficiency. A continuous wave （CW） single side output power of 160 mW was obtained for an uncoated laser with a 50μm active area width and 1 mm cavity length.
1.3-μm 1 × 4 MM1 coupler is designed and fabricated on an InP substrate based on a shallow etched waveguide structure. Tapered input/output waveguides and a bending waveguide design are adopted and applied in the device to optimize the performance. The average excess losses of the 1 × 4 MMI coupler per channel are 2.8, 1.7, 2.9, and 2.9 dB, respectively. The smallest excess loss can be lower than 0.5 dB in the 40-nm spectrum bandwidth. The average uniformity between the four channels of the MMI coupler is 1.3 dB, while the smallest uniformity is only 0.4 dB.
