High performance laterally gain coupled InGaAs/AlGaAs DFB lasers

We have investigated gain coupled lasers based on metal gratings patterned laterally to the laser ridge. For sufficiently small ridges, the evanescent field of the laser mode couples strongly to the grating. Ridge waveguide lasers were processed from an InGaAs/AlGaAs GRINSCH structure. The cw threshold currents are around 12 mA for a cavity with 800 μm length and 2.5 μm width. These values are comparable to reference lasers without metal grating, which shows that there is no significant penalty from loss coupling for a properly designed device. Pulsed monomode emission up to output power levels of 64 mW and sidemode supression ratios up to 45 dB have been obtained, indicating that the lateral coupling is strong enough for stable DFB operation