Tunnel junctions (TJs) are used to invert a relative arrangement of the built-in polarization and current flow direction for metal (Ill)-polar grown Ill-nitride laser diodes (LDs). The resulting devices has subsequent TJ, p-type layers, active region and n-type layers. This arrangement ensures a band alignment which provides an injection efficiency of 100% without the need of close proximity of an electron blocking layer.

An edge emitting laser (EEL) device includes a substrate, an n-type buffer layer, a first n-type cladding layer, a grating layer, a spacer layer, a lower confinement unit, an active layer, an upper confinement unit, a p-type cladding layer, a tunnel junction layer and a second n-type cladding layer sequentially arranged from bottom to top. The tunnel junction layer can stop an etching process from continuing to form the second n-type cladding layer into a predetermined ridge structure and converting a part of the p-type cladding layer into the n-type cladding layer to reduce series resistance of the EEL device. Therefore, the optical field and active layer tend to be coupled at the middle of the active layer, the lower half of the active layer can be utilized effectively, and the optical field is near to the grating layer to achieve better optical field/grating coupling efficiency and lower threshold current.

A vertical cavity surface emitting laser (VCSEL) device includes a substrate, a first mirror layer, a tunnel junction layer, a second mirror layer, an active layer, an oxide layer and a third mirror layer sequentially stacked with one another. The first mirror layer and the third mirror layer are N-type distributed Bragg reflectors (N-DBR), and the second mirror layer is P-type distributed Bragg reflector (P-DBR). The tunnel junction layer is provided for the VCSEL device to convert a part of the P-DBR into N-DBR to reduce the series resistance of the VCSEL device, and the tunnel junction layer is not used as current-limiting apertures. This disclosure further discloses a VCSEL device manufacturing method with the in-situ and one-time epitaxy features to avoid the risk of process variation caused by moving the device into and out from an epitaxial cavity.

VCSELs designed to emit light at a characteristic wavelength in a wavelength range of 910-2000 nm and formed on a silicon substrate are provided. Integrated VCSEL systems are also provided that include one or more VCSELs formed on a silicon substrate and one or more electrical, optical, and/or electro-optical components formed and/or mounted onto the silicon substrate. In an integrated VCSEL system, at least one of the one or more electrical, optical, and/or electro-optical components formed and/or mounted onto the silicon substrate is electrically or optically coupled to at least one of the one or more VSCELs on the silicon substrate. Methods for fabricating VCSELs on a silicon substrate and/or fabricating an integrated VCSEL system are also provided.

A multi-junction VCSEL is formed by as a compact structure that reduces lateral current spreading by reducing the spacing between adjacent active regions in the stack of such regions used to from the multi-junction device. At least two of the active regions within the stack are located adjacent peaks of the intensity profile of the VCSEL, with an intervening tunnel junction positioned at a trough between the two peaks. The alignment of the active regions with the peaks maximizes the generated optical power, while the alignment of the tunnel junction with the trough minimizes optical loss. The close spacing on adjacent peaks forms a compact structure (which may even include a cavity having a sub-λ optical length) that lessens the total path traveled by carriers and therefore reduces lateral current spread.

A multi-junction VCSEL is formed by as a compact structure that reduces lateral current spreading by reducing the spacing between adjacent active regions in the stack of such regions used to from the multi-junction device. At least two of the active regions within the stack are located adjacent peaks of the intensity profile of the VCSEL, with an intervening tunnel junction positioned at a trough between the two peaks. The alignment of the active regions with the peaks maximizes the generated optical power, while the alignment of the tunnel junction with the trough minimizes optical loss. The close spacing on adjacent peaks forms a compact structure (which may even include a cavity having a sub-λ optical length) that lessens the total path traveled by carriers and therefore reduces lateral current spread.

A semiconductor laser epitaxial structure includes a horizontal cavity configured to generate an optical field distribution, a grating layer located within the optical field distribution, a first semiconductor optical amplifier disposed between a light-emitting surface of the semiconductor laser epitaxial structure and the horizontal cavity, and a first tunnel junction layer disposed between the horizontal cavity and the first semiconductor optical amplifier. The grating layer is configured to convert a horizontal light to a vertical light. The semiconductor laser epitaxial structure does not require alignment, the yield rate of manufacturing the semiconductor laser is increased, and the manufacturing cost and manufacturing processes can be reduced.

A monolithic edge emitting semiconductor laser comprising multiple laser diodes using aluminum indium gallium arsenide phosphide AlInGaAs/InGaAsP/InP material system, emitting in long wavelengths (1250 nm to 1720 nm). Each laser diode contains an active region comprising aluminium indium gallium arsenide quantum wells (AlInGaAs QW) and aluminium indium gallium arsenide (AlInGaAs) barriers and connected to the subsequent monolithic laser diode by highly doped, low bandgap and low resistive indium gallium arsenide junction called tunnel junction.

In order to provide a QCL element operating in the near-infrared wavelength range, the present disclosure provides a quantum cascade laser element 1000 having a semiconductor superlattice structure (QCL structure 100) sandwiched between a pair of conductive sections 20 and 30. The semiconductor superlattice structure serves as an active region that emits electromagnetic waves. The active region has a plurality of unit structures 10U that are stacked on top of each other. Each unit structure includes four well layers 10W1-10W4 of a composition of Al.sub.xGa.sub.1-xN, separated from each other by barrier layers 10B1-10B5 of a composition of Al.sub.yGa.sub.1-yN with 0≤x<y≤1. Both of the conductive sections in the pair of conductive sections have a refractive index lower than that of the active region in which doped TCO inserted as a key role.

The disclosure describes VCSELs operable to produce very narrow divergent light beams. The narrow divergent beam can be obtained, in part, by incorporating an additional epitaxial layer so as to increase the cavity length of the VCSEL. The increased cavity length can result in higher power in fewer larger diameter transverse modes, which can significantly reduce the output beam divergence. The additional epitaxial layer can be incorporated, for example, into a top-emitting VCSEL or bottom-emitting VCSEL.