High-performance 1.55-μm wavelength GaInAsP-InP distributed-feedback lasers with wirelike active regions

High-performance 1.55-mum wavelength GaInAsP-InP strongly index-coupled and gain-matched distributed-feedback (DFB) lasers with periodic wirelike active regions were fabricated by electron beam lithography, CH4/H-2-reactive ion etching, and organometallic vapor-phase epitaxial regrowth, whose index-coupling coefficient was more than 300 cm(-1). In order to design lasers for low threshold current operation, threshold current dependences on the number of quantum wells and the wire width were investigated both theoretically and experimentally. A record low threshold current density of 94 A/cm(2) among 1.55-mum DFB lasers was successfully obtained for a stripe width of 19.5 mum and a cavity length of 600 mum. Moreover, a record low threshold current of 0.7 mA was also realized at room temperature under CW condition for a 2.3-mum-wide buried heterostructure with a 200-mum-long cavity. Finally, we confirmed stable single-mode operation due to a gain-matching effect between the standing-wave profile and the wirelike active region.