Design and fabrication of 1.5 ¿m ridge waveguide distributed feedback lasers

The paper describes the design and fabrication of distributed feedback lasers operating at around 1.5 ¿m, which utilise the ridge waveguide design for lateral mode and current confinement. The design considerations presented concentrate on the optimisation of waveguide layer compositions and thicknesses, together with the appropriate selection of diffraction-grating profile, in order to obtain strong grating coupling with the optical wave in the final device. We show that the devices made have operating characteristics comparable with the best DFB laser results so far reported. The high modulation capabilities afforded by the ridge waveguide structure are also demonstrated, and systems results show conclusively the high potential of these devices for future long-haul, high-bandwidth optical communication systems.