980 nm Al-free ridge waveguide distributed feedback lasers with lateral gain coupling

We present Al-free gain-coupled lasers emitting at 980 nm with metal gratings patterned laterally to the laser waveguide. The process is based on standard ridge waveguide fabrication and requires no regrowth. For a sufficiently small waveguide, the evanescent field of the laser mode couples to the lateral grating. Ridge waveguide lasers were processed from an MOCVD grown Al free laser structure with a single InGaAs quantum well. The cw threshold currents are around 17 mA for a 1 mm long laser, differential efficiencies are 0.2 W/A. Monomode emission up to output power levels of 25 mW and sidemode suppression ratios of 45 dB have been obtained. The lasers are monomode over a wide range of temperature and current, indicating that the lateral coupling is sufficiently strong for stable DFB operation