An edge emitter semiconductor laser type device that comprises in a longitudinal direction, between two mirrors:
- a main segment;
- and
- between the main segment and one of the two mirrors, at least one end segment for protecting that mirror;
- the main segment comprising a main layered optical transversal structure with selected optical properties, which allows, in the longitudinal direction, preferentially the amplification of a transversal fundamental mode, the main layered optical transversal structure comprising:
- a core waveguide that includes an active region;
- an upper cladding, containing the radiation that extends above of the core waveguide;
- a lower cladding, containing the radiation that extends bellow of the core waveguide, the lower cladding being thicker than the upper cladding;
- the lower cladding containing a trapping waveguide that constitutes together with the core waveguide a double waveguide;
- the lower cladding having on average a higher refractive index than that of the upper cladding;
- the refractive index profile of the transversal structure being asymmetric, the radiation field of the fundamental mode is preponderantly distributed on the lower side of the optical structure;
- the double waveguide is designed for the preferential amplification of the fundamental transversal mode, which is the best coupled with the active region and has the highest confinement factor among all modes;
- in the end segment, a taper is formed by a plurality of transitory layered optical transversal structures derived from the main layered optical transversal structure of the main segment by gradually reducing the thickness of the upper cladding,
- wherein the field distribution of the fundamental transversal mode remains trapped by the double waveguide as the thickness of the upper cladding is gradually reduced;
- wherein the tapered segment has the role of reducing the confinement factor of the fundamental transversal mode traversing the end segment by shifting the field distribution from the core waveguide to the trapping waveguide and the role of reducing losses from the fundamental transversal mode that propagates in the tapered segment;
- the reduction of the confinement factor of the fundamental transversal mode being dependent on the last transversal structure of the plurality of transitory transversal structures, while the losses from the fundamental transversal mode being dependent on the length of the end segment and on the way the thickness is reduced along the end segment;
- and
- wherein, when the confinement factor for the fundamental transversal mode decreases by up to five times, determining a corresponding increase of resilience against degradation of the protected mirror, the losses from the fundamental transversal mode are reduced to less than 10%.