Wavelength tunable single-mode metal-clad ridge-waveguide lasers for 1.55 μm wavelength region

Electronically tunable two-section distributed feedback lasers with metal-clad ridge-waveguide structure are reported. These lasers have been fabricated by two-stage liquid-phase epitaxy and utilize a first order Bragg grating for wavelength selective feedback. They emit in a single longitudinal mode over a continuous tuning range of about 1 nm (125 GHz) with a linewidth less than 40 MHz. The low threshold currents around 34 mA for 400 μm long devices and the tuning characteristics agree fairly well with a newly developed analytical model for multisection distributed feedback lasers. Due to the comparatively simple fabrication technique and the excellent long-term stability of the basic metal-clad ridge-waveguide structure, these devices are potentially useful for coherent optical fiber transmission systems and wavelength division multiplexing applications.