Abstract: An optical waveguide includes, in monolithic manner, a rear segment, a transition segment, and a front segment extending and succeeding one another along the length of the waveguide. A lateral confinement factor and a width the waveguide are respectively larger and smaller in the rear segment than in the front segment. According to the invention, the width increases in the transition segment until it reaches a value that is larger than that of the front segment. The invention is particularly applicable to integrating together a laser and an optical modulator for a telecommunications system.

Abstract: The invention concerns an optical waveguide transition and its fabrication method, enabling coupling between a buried optical waveguide and a ridged optical waveguide. The transition structure is formed during etching of a layer containing the buried optical waveguide, the transition area being formed by adiabatically increasing the lateral dimensions of the buried waveguide. Top layers are deposited on the buried waveguide and its widened structure in the transition area, and the ridged optical waveguide is fabricated with one part on top of the transition area. Coupling of the respective propagation modes in the buried and ridged waveguides is effected by mode adaptation in the region between the two waveguide structures in the transition area. The transition of the invention is made in two conventional epitaxy steps.