Well number design for 1.5-µm band multiple-quantum-well distributed feedback laser diodes

Recently, distinguishable lasing characteristics, such as low-chirp single-frequency operation under high-speed direct modulation1 and 2.1-MHz narrow spectral linewidth,2 have been reported for 1.5-μm band InGaAs multiple-quantum-well distributed feedback laser diodes (MQW DFB LDs). Although the device parameter dependence of lasing characteristics has been theoretically predicted,3,4 thus far no clear strategy for designing practical MQW-DFB LDs has been reported. As the InGaAs well width is fixed for light emission at a desired 1.5-μm wavelength region, the well number should be the most influential design parameter. This paper reports the first experimental investigation on the well number design in 1.5-μm MQW DFB LDs for direct-detection and coherent-detection optical communication systems.