High-performance distributed feedback quantum dot lasers with laterally coupled dielectric gratings

The combination of grating-based frequency-selective optical feedback mechanisms,such as distributed feedback(DFB)or distributed Bragg reflector(DBR)structures,with quantum dot(QD)gain materials is a main approach towards ultrahigh-performance semiconductor lasers for many key novel applications,as either stand-alone sources or on-chip sources in photonic integrated circuits.However,the fabrication of conventional buried Bragg grating structures on GaAs,GaAs/Si,GaSb,and other material platforms has been met with major material regrowth difficulties.We report a novel and universal approach of introducing laterally coupled dielectric Bragg gratings to semiconductor lasers that allows highly controllable,reliable,and strong coupling between the grating and the optical mode.We implement such a grating structure in a low-loss amorphous silicon material alongside GaAs lasers with InAs/GaAs QD gain layers.The resulting DFB laser arrays emit at pre-designed 0.8 THz local area network wavelength division multiplexing frequency intervals in the 1300 nm band with record performance parameters,including sidemode suppression ratios as high as 52.7 dB,continuous-wave output power of 26.6 mW(room temperature)and 6 mW(at 55℃),and ultralow relative intensity noise(RIN)of<-165 dB/Hz(2.5-20 GHz).The devices are also capable of isolator-free operating under very high external reflection levels of up to-12.3 dB while maintaining high spectral purity and ultralow RIN qualities.These results validate the novel laterally coupled dielectric grating as a technologically superior and potentially cost-effective approach for fabricating DFB and DBR lasers free of their semiconductor material constraints,which are thus universally applicable across different material platforms and wavelength bands.