Membrane III-V/Si DFB Laser Using Uniform Grating and Width-Modulated Si Waveguide

Membrane buried-heterostructure III-V/Si distributed feedback (DFB) lasers with a stopband-modulated cavity on a Si substrate have been developed. The membrane III-V layers with 230-nm thickness enable us to construct an optical supermode with a 220-nm-thick Si waveguide that is used in standard Si photonics platform. We employ a uniform grating and Si waveguide, in which Si waveguide width is modulated to control the center wavelength of the stopband. The cavity can be designed by controlling the modulation width and modulation length of Si waveguide. Therefore, it is easy to engineer and fabricate the laser cavity compared with the cavity using λ/4-phase shift grating. Output light from the cavity is coupled to Si waveguide through InP inverse taper waveguide, and then coupled to SiO_x waveguide through Si inverse taper waveguide, which provides the 2-dB fiber coupling loss. We have demonstrated single-mode lasing by using Si waveguide, where its width is increased 80 nm at the center of the cavity. The threshold current and maximum fiber output power are 3 mA and 4 mW, respectively. By extending the active region length to 1 mm, 17-mW fiber coupled output power is obtained. High-temperature operation up to 130 °C is also obtained with a 1-mW fiber output power.