InGaAsP ridge waveguide distributed feedback lasers operating near 1.55 µm

Fabrication and performance of ridge waveguide distributed feedback lasers grown by liquid phase epitaxy for operation in the 1.50-1.58 μm spectral region have been studied. These lasers incorporate first- and second-order diffraction gratings written by the electron beam lithography and optical holography and defined by wet chemical etching and novel ion-beam-milling techniques. Ridge waveguides were formed by post-regrowth processing and heteroepitaxial ridge overgrowth. Distributed feedback ridge lasers were characterized by room temperature CW threshold currents as low as 40 mA, two facet external quantum efficiencies of up to 40 percent and stable transverse mode operation up to the output power of 10 mW. In strongly coupled devices, even with a cleaved resonator, the Bragg mode intensity exceeds that of the residual Fabry-Perot modes by a factor of 4000:1. Stable, single longitudinal mode operation was obtained under modulation rates as high as 4 GHz and error free transmission experiments over 60-km lengths of single mode fiber reproducibly performed at data rates as high as 2 Gbit/s.