Provided here are: a mesa strip which has an n-type cladding layer, an active layer and a p-type cladding layer that are stacked sequentially on a surface of an n-type substrate; Fe-doped semi-insulating layers which are embedded along both sides of the mesa stripe, each up to a height higher than the mesa stripe; n-type blocking layers which are stacked on respective surfaces of the Fe-doped semi-insulating layers located on the both sides of the mesa stripe, and which are spaced apart from each other with an interval that is a space corresponding to a central portion of the active layer and is thus narrower than the active layer; p-type cladding layers which are formed on back surfaces of respective mesa-stripe-side end portions of the n-type blocking layers; and a p-type cladding layer which buries a top of the mesa stripe, the p-type cladding layers and the n-type blocking layers.

An optical semiconductor device outputting a predetermined wavelength of laser light includes a quantum well active layer positioned between a p-type cladding layer and an n-type cladding layer in thickness direction. The optical semiconductor device includes a separate confinement heterostructure layer positioned between the quantum well active layer and the n-type cladding layer. The optical semiconductor device further includes an electric-field-distribution-control layer positioned between the separate confinement heterostructure layer and the n-type cladding layer and configured by at least two semiconductor layers having band gap energy greater than band gap energy of a barrier layer constituting the quantum well active layer. The quantum well active layer is doped with 0.3 to 1×10.sup.18/cm.sup.3 of n-type impurity.

This optical semiconductor element includes: a substrate; a first ridge formed on the substrate and having a first first-conductivity-type cladding layer, a first core layer, a first second-conductivity-type cladding layer, and a first contact layer in this order from a lower side, with first ridge grooves provided on both lateral sides of the first ridge; and a first electrode formed in contact with the first contact layer, on the first ridge, without spreading to the first ridge grooves, the first electrode including a first solder layer.

Example vertical cavity surface emitting lasers (VCSELs) include a mesa structure disposed on a substrate, the mesa structure including a first reflector, a second reflector defining at least one diameter, and an active cavity material structure disposed between the first and second reflectors; and a second contact layer disposed at least in part on top of the mesa structure and defining a physical emission aperture having a physical emission aperture diameter. The ratio of the physical emission aperture diameter to the at least one diameter is greater than or approximately 0.172 and/or the ratio of the physical emission aperture diameter to the at least one diameter is less than or approximately 0.36. An example VCSEL includes a substrate; a buffer layer disposed on a portion of the substrate; and an emission structure disposed on the buffer layer.

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 aluminum indium gallium arsenide (AlInGaAs) barriers and is connected to the subsequent monolithic laser diode by highly doped, low bandgap and low resistive indium gallium arsenide junction called tunnel junction.

Building blocks are provided for on-chip chemical sensors and other highly-compact photonic integrated circuits combining interband or quantum cascade lasers and detectors with passive waveguides and other components integrated on a III-V or silicon. A MWIR or LWIR laser source is evanescently coupled into a passive extended or resonant-cavity waveguide that provides evanescent coupling to a sample gas (or liquid) for spectroscopic chemical sensing. In the case of an ICL, the uppermost layer of this passive waveguide has a relatively high index of refraction that enables it to form the core of the waveguide, while the ambient air, consisting of the sample gas, functions as the top cladding layer. A fraction of the propagating light beam is absorbed by the sample gas if it contains a chemical species having a fingerprint absorption feature within the spectral linewidth of the laser emission.

A semiconductor laser device includes a laser section and a modulator section. The laser section has: a first mesa stripe which is formed on a semiconductor substrate; semi-insulative burying layers which are placed to abut on both side surfaces of the first mesa stripe and are formed on the semiconductor substrate; n-type burying layers formed on respective surfaces of the semi-insulative burying layers; and a p-type cladding layer which covers surfaces of the n-type burying layers and the first mesa stripe. The modulator section has: a second mesa stripe which is formed on the semiconductor substrate; semi-insulative burying layers which are placed to abut on both side surfaces of the second mesa stripe and are formed on the semiconductor substrate; and a p-type cladding layer which covers surfaces of the semi-insulative burying layers and the second mesa stripe.

In some implementations, a vertical cavity surface emitting laser (VCSEL) device includes a substrate; a first mirror disposed over the substrate; a bonding layer disposed over the first mirror; and an active region disposed over the bonding layer. The substrate is a gallium arsenide (GaAs) substrate, and the active region is an indium phosphide (InP)-based active region.

A vertical-cavity surface-emitting laser (VCSEL) may include a substrate. The VCSEL may include a bottom mirror structure over the substrate. The VCSEL may include a first dilute nitride active region over the bottom mirror structure. The VCSEL may include a tunnel junction over the first dilute nitride active region. The VCSEL may include a second dilute nitride active region over the tunnel junction. The VCSEL may include a top mirror structure over the second dilute nitride active region.

A semiconductor optical device includes an SOI substrate having a waveguide of silicon, and at least one gain region of a group III-V compound semiconductor having an optical gain bonded to the SOI substrate. The waveguide has a bent portion and multiple linear portions extending linearly and connected to each other through the bent portion. The gain region is disposed on each of the multiple linear portions.