A QCL may include a substrate, and a semiconductor layer adjacent the substrate. The semiconductor layer may define branch active regions, and a stem region coupled to output ends of the branch active regions. Each branch active region may have a number of stages less than 30.

The semiconductor light-emitting element includes: a stacking structure having a substrate and a semiconductor layer between a first surface and a second surface that face each other in order from a side on which the first surface is located, the substrate including a compound semiconductor, and the semiconductor layer being crystal-grown on the substrate and including a light-emitting region; a first depression formed on at least a portion of a first edge adjacent to the second surface of the stacking structure; and a second depression formed on a second edge extending along a thickness direction of the stacking structure.

A quantum cascade laser including: a laser structure having a first region including a first facet, a second region including a second facet, an epitaxial surface, and a substrate surface; an insulating film disposed on the second facet and the epitaxial surface; an electrode disposed on the epitaxial surface and the insulating film and in contact with the epitaxial surface; and a metal film disposed over the second facet and the epitaxial surface and separated from the electrode and the substrate surface. The insulating film is disposed between the metal film and the second facet and between the metal film and the epitaxial surface. The second region includes a semiconductor mesa. The second facet is located at a boundary between the first region and the second region. The first region includes a connecting surface. The connecting surface connects the second facet to the first facet.

In a semiconductor laser device, a semiconductor layer includes a first groove formed on both sides of a ridge, a pair of second recesses facing each other and between which the ridge is interposed on a side of a light emitting surface, and a pair of third grooves in parallel to the first groove from the light emitting surface and interposing the ridge therebetween.

A laser diode includes a semiconductor body having a substrate and a semiconductor layer sequence arranged on the substrate, which includes an active zone that generates electromagnetic radiation, wherein the semiconductor body has a first main surface and a second main surface opposite the first main surface and at least one first and second laser facet, which are respectively arranged transversely to the first and second main surfaces, and at least one structured facet region located at a transition between the first main surface and at least one of the first and second laser facets, and the structured facet region includes at least a strained compensation layer or a recess.

A semiconductor laser device includes an optical waveguide that extends toward a first end of the semiconductor laser device. The optical waveguide includes a first clad layer, an active layer, a second clad layer, and an electrode layer in this order. A reflecting surface, which has a dielectric film and a metal film in this order from the active layer, crosses the active layer at a second end of the optical waveguide.

Described herein is a two chip photonic device (e.g., a hybrid master oscillator power amplifier (MOPA)) where a gain region and optical amplifier region are formed on a III-V chip and a variable reflector (which in combination with the gain region forms a laser cavity) is formed on a different semiconductor chip that includes silicon, silicon nitride, lithium niobate, or the like. Sides of the two chips are disposed in a facing relationship so that optical signals can transfer between the gain region, the variable reflector, and the optical amplifier.

Exemplary embodiments of the present disclosure include chip-scale laser sources, such as semiconductor laser sources, that produce directional beams with low spatial coherence. The lasing modes are based on the axial orbit in a stable cavity and have good directionality. To reduce the spatial coherence of emission, the number of transverse lasing modes can be increased by fine-tuning the cavity geometry. Decoherence is reached in as little as several nanoseconds. Such rapid decoherence facilitates applications in ultrafast speckle-free full-field imaging.

A semiconductor laser device includes: a layered structure in which a first conductivity type cladding layer, an active layer, a second conductivity type cladding layer, and a contact layer are layered in a first direction, the layered structure including a facet in a second direction intersecting the first direction, the facet outputting laser light, a non-window region, and a window region, the window region having a bandgap larger than a bandgap of the non-window region; a first electrode electrically connected to the first conductivity type cladding layer; a second electrode that is formed on the contact layer and constitutes a current path through the layered structure with the first electrode; a passivation layer formed on the facet and having a bandgap larger than the bandgap of the window region; and a dielectric reflecting coating configured to cover an opposite side of the passivation layer from the facet.

A gallium- and nitrogen-containing laser device including an etched facet with surface treatment to improve an optical beam is disclosed.