The present technology can be used to control the current injection profile in the longitudinal direction of a high-power diode laser in order to optimize current densities as a function of position in the cavity to promote higher reliable output power and increase the electrical to optical conversion efficiency of the device beyond the level which can be achieved without application of this technique. This approach can be utilized, e.g., in the fabrication of semiconductor laser chips to improve the output power and wall plug efficiency for applications requiring improved performance operation.

A semiconductor laser element that includes a semiconductor layer including a waveguide formed in an intra-layer direction of the semiconductor layer and a window region formed in a front-side end face of the waveguide, has a current-laser optical output characteristic in which, at an operating temperature of 25 C.3 C., a laser optical output has a maximum value at a first driving current value and the laser optical output is at most 20% of the maximum value at a second driving current value greater than the first driving current value, and is not damaged at the second driving current value.

A laser chip including a plurality of stripes is disclosed, where a laser stripe can be grown with an initial optical gain profile, and its optical gain profile can be shifted by using an intermixing process. In this manner, multiple laser stripes can be formed on the same laser chip from the same epitaxial wafer, where at least one laser stripe can have an optical gain profile shifted relative to another laser stripe. For example, each laser stripe can have a shifted optical gain profile relative to its neighboring laser stripe, thereby each laser stripe can emit light with a different range of wavelengths. The laser chip can emit light across a wide range of wavelengths. Examples of the disclosure further includes different regions of a given laser stripe having different intermixing amounts.

A quantum cascade laser having a laser structure that includes a semiconductor mesa, a first end surface, a second end surface, and a first electrode provided on the semiconductor mesa. The laser structure includes a first region having the first end surface and a second region located between the second end surface and the first region. The semiconductor mesa includes a first mesa portion and a second mesa portion that are respectively included in the first region and the second region. The semiconductor mesa includes a first superlattice layer, a second superlattice layer, and a conductive semiconductor region. The first superlattice layer extends from the first end surface in the second axis direction and is included in the first mesa portion and the second mesa portion, and the second superlattice layer is provided in one of the first mesa portion and the second mesa portion.

A semiconductor laser device includes a semiconductor layer portion having an active layer and performs multi-mode oscillation of laser light. Further, the semiconductor layer portion includes first and second regions, the second region being located closer to a facet on a laser light radiation side than the first region, the first region and the second region include a stripe region in which the laser light is guided, and an optical confinement effect of the laser light to the stripe region in a horizontal direction in the second region is less than that in the first region.

A semiconductor laser device includes a semiconductor layer portion having an active layer and performs multi-mode oscillation of laser light. Further, the semiconductor layer portion includes first and second regions, the second region being located closer to a facet on a laser light radiation side than the first region, the first region and the second region include a stripe region in which the laser light is guided, and an optical confinement effect of the laser light to the stripe region in a horizontal direction in the second region is less than that in the first region.

A quantum cascade laser includes: a laser structure including first and second end faces, a semiconductor mesa, and a supporting base; and a first electrode on the semiconductor mesa. The first and second end faces are arranged in a direction of a first axis. The semiconductor mesa has first and second mesa portions which are disposed between the first and second end faces. The semiconductor mesa has a first mesa width at a boundary between the first and second mesa portions, and a second mesa width smaller than the first mesa width at an end of the second mesa portion, and has a width varying from the first mesa width in a direction from the boundary to the second end face. The second mesa portion includes a high specific-resistance region having a specific-resistance higher than that of a conductive semiconductor region included in the first and second mesa portions.

A semiconductor laser includes a semiconductor layer sequence having an n-conducting n-region, a p-conducting p-region and an intermediate active zone, an electrically conductive p-contact layer that impresses current directly into the p-region and is made of a transparent conductive oxide, and an electrically conductive and metallic p-contact structure located directly on the p-contact layer, wherein the semiconductor layer sequence includes two facets forming resonator end faces for the laser radiation, in at least one current-protection region directly on at least one of the facets a current impression into the p-region is suppressed, the p-contact structure terminates flush with the associated facet so that the p-contact structure does not protrude beyond the associated facet and vice versa, and the p-contact layer is removed from at least one of the current-protection regions and in this current-protection region the p-contact structure is in direct contact with the p-region over the whole area.

A semiconductor laser includes a semiconductor layer sequence having an n-conducting n-region, a p-conducting p-region and an intermediate active zone, an electrically conductive p-contact layer that impresses current directly into the p-region and is made of a transparent conductive oxide, and an electrically conductive and metallic p-contact structure located directly on the p-contact layer, wherein the semiconductor layer sequence includes two facets forming resonator end faces for the laser radiation, in at least one current-protection region directly on at least one of the facets a current impression into the p-region is suppressed, the p-contact structure terminates flush with the associated facet so that the p-contact structure does not protrude beyond the associated facet and vice versa, and the p-contact layer is removed from at least one of the current-protection regions and in this current-protection region the p-contact structure is in direct contact with the p-region over the whole area.

A quantum cascade laser includes a laser structure including first and second end faces, the laser structure including a semiconductor laminate region and a first embedding semiconductor region. The laser structure includes first and second regions arranged in a direction of a first axis extending from the first to second end faces. Each of the first and second regions includes the semiconductor laminate region. The semiconductor laminate region of the first region has a first recess. The semiconductor laminate region of the second region has a semiconductor mesa. The first recess and the semiconductor mesa extend in the direction of the first axis, and are aligned with each other. The semiconductor mesa has an end face extending in a direction of a second axis intersecting the first axis. The first embedding semiconductor region is disposed in the first recess so as to embed the end face of the semiconductor mesa.