Low-threshold and high-efficiency operation of distributed reflector lasers with width-modulated wirelike active regions

1.55-μm-wavelength distributed reflector (DR) lasers with low threshold and high efficiency were realized which consisted of a distributed feedback (DFB) grating and high-reflection distributed Bragg reflector (DBR) sections integrated by utilizing the lateral quantum confinement effect in a quantum-wire structure. In order to realize a high-performance DR laser, the high-reflection DBR structure was investigated theoretically and experimentally and could be fabricated with a reflectivity of over 90%, taking into consideration the absorption in the active layers. The highest differential quantum efficiency of 36% from the front facet was obtained for the 4.4-μm stripe width and 300-μm DFB section length under room temperature (RT) and continuous-wave (CW) conditions. Moreover, the lowest threshold current of 1.5 mA was obtained for the 3.4-μm stripe width and 150-μm DFB length.