A semiconductor optical device includes a first n-type III-V group compound semiconductor layer, an active layer, a tunnel junction structure including a p-type III-V group compound semiconductor layer and a second n-type III-V group compound semiconductor layer, and a third n-type III-V group compound semiconductor layer. The first n-type III-V group compound semiconductor layer, the active layer, the p-type III-V group compound semiconductor layer, the second n-type III-V group compound semiconductor layer, and the third n-type III-V group compound semiconductor layer are stacked in this order. The second n-type III-V group compound semiconductor layer has an n-type dopant concentration higher than an n-type dopant concentration of the third n-type III-V group compound semiconductor layer. The p-type III-V group compound semiconductor layer has a strain.

An optical semiconductor device includes a multi-quantum well layer including well layers and barrier layers alternately overlapping with each other, an optical confinement layer, and a guide layer interposed between the multi-quantum well layer and the optical confinement layer. Each barrier layer is an undoped layer and an outermost layer is one of the barrier layers. The optical confinement layer has a refractive index that is greater than that of the outermost layer and a band gap that is smaller than that of the outermost layer. The guide layer includes a first adjacent layer in contact with the outermost layer and the guide layer is thinner than the optical confinement layer. Each of the optical confinement layer and the guide layer is an n-type semiconductor layer. The first adjacent layer of the guide layer has a band gap that is larger than that of the optical confinement layer.

An optical device has a gallium and nitrogen containing substrate including a surface region and a strain control region, the strain control region being configured to maintain a quantum well region within a predetermined strain state. The device also has a plurality of quantum well regions overlying the strain control region.

Included are embodiments of a quantum cascade laser structure. Some embodiments include a plurality of quantum wells and a plurality of barriers, at least a portion of which define an active region. In some embodiments, a photon is emitted in the active region when an electron transitions from an upper laser state in the active region to a lower laser state in the active region. Additionally, a final quantum well in the plurality of quantum wells may define the active region, where the final quantum well extends below an adjacent quantum well in the active region. Similarly, the final quantum well may include a thickness that is less than a thickness of the adjacent quantum well in the active region.

A surface-emitting laser device includes: a first reflector; a second reflector; and a resonator region between the first reflector and the second reflector. The resonator region includes: multiple active layers each having first crystal strain in one of a compression direction and a tension direction; a tunnel junction layer between the multiple active layers; and a strain relaxation layer having second crystal strain in another of the compression direction and the tension direction opposite to the first crystal strain of the multiple active layers.

A semiconductor optical device (40, 50, 60) comprises a first region 42 comprising an active region configured such that electrons and holes recombine in the active region to produce photons when a voltage is applied to the device. The device comprises at least one second region (43, 44, 53, 54, 62, 63) comprising a quantum well structure which is configured to trap electrons only, to trap holes only, or to trap different amounts of electrons and holes. The second region is arranged at a distance from the first region which is sufficiently close to the first region such that a charge imbalance develops in the first region when a voltage is applied to the device, thereby to reduce Auger recombination in the first region.

A vertical cavity surface-emitting laser configured to emit laser light having a wavelength of 830 nm to 910 nm includes a substrate having a main surface including GaAs, a first distributed Bragg reflector, an active layer, and a second distributed Bragg reflector. The substrate, the first distributed Bragg reflector, the active layer, and the second distributed Bragg reflector are arranged in a first axis direction intersecting the main surface. The main surface has an off angle of 6 or more with respect to a (100) plane. The active layer includes In.sub.xAl.sub.yGa.sub.1-x-yAs (0<x<1, 0y<1). The active layer has a strain. An absolute value of the strain is 0.5% to 1.4%.

A device includes: a laminate including first and second regions adjacent to respective both sides of an isolation groove; a mesa stripe structure adjacent to the first region on the laminate and extending in the first direction; a bank structure adjacent to the second region on the laminate and extending in the first direction; and an electrode pattern. The isolation groove has an inner surface including a first wall surface adjacent to the first region, a second wall surface adjacent to the second region, and a bottom surface between the first and second regions. The ridge electrode extends from the side of the mesa stripe structure, along a second direction, toward the bank structure, and not beyond the second wall surface. The connection electrode is narrower in width in the first direction than any one of the ridge electrode and the pad electrode.

Provided is an epitaxial chip structure. The epitaxial chip structure includes a substrate, a preparation layer, a buffer layer, a base layer, and an active layer, where the preparation layer, the buffer layer, the base layer, and the active layer are sequentially stacked on the substrate. The buffer layer is arranged as a multilayer In component gradient growth structure of In.sub.xGa.sub.yAl.sub.zN (0<x100%; x+y+z=1) compound material, and the lattice constant of a material of the buffer layer is the same as or similar to the lattice constant of a material of the active layer.

Some embodiments may include a laser diode having a strain-engineered cladding layer for optimized active region strain and improved laser diode performance. In one embodiment, the laser diode may include a semiconductor substrate having a material composition with a first lattice constant; and a plurality of epitaxy layers form on the semiconductor substrate, with plurality of epitaxy layers including a waveguide layer and cladding layers, wherein the waveguide layer includes an active region having a material composition associated with a target optical wavelength, wherein a second lattice constant of the material composition of the active region is different than the first lattice constant; wherein a material composition and/or thickness of an individual cladding layer of the cladding layers is/are arranged to impart a target stress field on the active region to optimize active region strain. Other embodiments may be disclosed and/or claimed.