Complex coupled distributed-feedback and Bragg-reflector lasers for monolithic device integration based on focused-ion-beam technology

Complex coupled distributed feedback (CC-DFB) and distributed Bragg-reflector (DBR) GaInAsP-InP lasers were fabricated by focused-ion-beam lithography. Due to the high single-mode yield and the simplified process technology, these devices are very suitable for monolithic device integration for wavelength-division-multiplexing (WDM) components. In a two-section device with a grating and an electrically separated waveguide gain section, the combination of a DFB laser with a passive waveguide, as well as the operation as a DBR laser with an unpumped grating section was investigated. The DFB and DBR lasers show very high single-mode stability in terms of wavelength detuning, bias current and temperature. For DBR lasers, a side-mode suppression ratio of well above 50 dB was achieved over a current range of more than 10 times the threshold current. Due to the good detuning properties. DFB Lasers were strongly detuned to the long wavelength side to suppress band edge absorption in passive waveguide sections. For a 3-mm-long waveguide the absorption was reduced by more than 20 dB. Although ion implantation is involved in the fabrication process of the lasers lifetime measurements over more than 10000 h of continuous-wave (CW) operation at room temperature show no significant device degradation.