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 QCL may include a substrate, and a sequence of semiconductor epitaxial layers adjacent the substrate and defining an active region, an injector region adjacent the active region, and a waveguide optically coupled to the active region. The active region may include stages, each stage having an upper laser level and a lower laser level defining respective first and second wave functions. The upper laser level may have an upper laser level average coordinate, and the lower laser level may have a lower laser level average coordinate. The upper laser level average coordinate and the lower laser level average coordinate may have spacing of less than 10 nm. Wave functions for all active region energy levels located below the lower laser level may have greater than 10% overlap with the injector region.

A QCL may include a substrate, and a sequence of semiconductor epitaxial layers adjacent the substrate and defining an active region, an injector region adjacent the active region, and a waveguide optically coupled to the active region. The active region may include stages, each stage having an upper laser level and a lower laser level defining respective first and second wave functions. The upper laser level may have an upper laser level average coordinate, and the lower laser level may have a lower laser level average coordinate. The upper laser level average coordinate and the lower laser level average coordinate may have spacing of less than 10 nm. Wave functions for all active region energy levels located below the lower laser level may have greater than 10% overlap with the injector region.

[Object] To provide a laser element capable of preventing laser characteristics from deteriorating while suppressing electron overflow and improving the yield at the time of production.

[Solving Means] A laser element according to the present technology includes: a first semiconductor layer; a second semiconductor layer; an active layer; and an electron barrier layer. The first semiconductor layer is formed of a group iii nitride semiconductor having a first conducive type. The second semiconductor layer is formed of a group iii nitride semiconductor having a second conductive type. The active layer is formed of a group iii nitride semiconductor and is provided between the first semiconductor layer and the second semiconductor layer. The electron barrier layer is provided between the active layer and the second semiconductor layer and is formed of a group iii nitride semiconductor having a composition ratio of Al larger than that of the second semiconductor layer, a recessed and projecting shape being formed on a surface of the electron barrier layer on a side of the second semiconductor layer, the recessed and projecting shape having a height difference between a projecting portion and a recessed portion in a direction perpendicular to a layer surface direction being 2 nm or more and less than 10 nm.

A vertical cavity surface emitting laser (VCSEL) has first and second electrical contacts, and an optical resonator. The optical resonator has first and second distributed Bragg reflectors (DBRs), an active layer, a distributed heterojunction bipolar phototransistor (DHBP), and an optical guide. The DHBP has a collector layer, light sensitive layer; a base layer; and an emitter layer. There is an optical coupling between the active layer and the DHBP for providing an active carrier confinement by the DHBP. The optical guide guides an optical mode within the optical resonator during operation. The optical guide is outside a current flow which can be provided by the first and second electrical contacts during operation of the VCSEL. The optical guide is outside a layer sequence between the first and second electrical contacts in the vertical direction of the VCSEL. The optical guide has an oxide aperture arranged in the second DBR.

In an embodiment a semiconductor laser diode includes a semiconductor layer sequence comprising an active layer having a main extension plane, the semiconductor layer sequence configured to generate light in an active region and radiate the light via a light-outcoupling surface, wherein the active region extends from a rear surface opposite the light-outcoupling surface to the light-outcoupling surface along a longitudinal direction in the main extension plane and a continuous contact structure directly disposed on a surface of the semiconductor layer sequence, wherein the contact structure comprises in at least a first contact region a first electrical contact material in direct contact with the surface region and in at least a second contact region a second electrical contact material in direct contact with the surface region, wherein the first and second contact regions adjoin one another.

Integrated-optics systems are presented in which an optically active device is optically coupled with a silicon waveguide via a passive compound-semiconductor waveguide. In a first region, the passive waveguide and the optically active device collectively define a composite waveguide structure, where the optically active device functions as the central ridge portion of a rib-waveguide structure. The optically active device is configured to control the vertical position of an optical mode in the composite waveguide along its length such that the optical mode is optically coupled into the passive waveguide with low loss. The passive waveguide and the silicon waveguide collectively define a vertical coupler in a second region, where the passive and silicon waveguides are configured to control the distribution of the optical mode along the length of the coupler, thereby enabling the entire mode to transition between the passive and silicon waveguides with low loss.

A semiconductor laser is formed to include a current blocking layer that is positioned below the active region of the device and used to minimize current spreading beyond the defined dimensions of an output beam's optical mode. When used in conjunction with other current-confining structures typically disposed above the active region (e.g., ridge waveguide, electrical isolation, oxide aperture), the inclusion of the lower current blocking layer improves the efficiency of the device. The current blocking layer may be used in edge-emitting devices or vertical cavity surface-emitting devices, and also functions to improve mode shaping and reduction of facet deterioration by directing current flow away from the facets.

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 layered structure comprising a substrate having a first deformation. Also one or more device layers forming a device and having a second deformation. A deformation control layer which is pseudomorphic with respect to the substrate and having a third deformation. The deformation control layer is selected such that a sum of the first, second and third deformations matches a target level of deformation. Advantageously the layered structure has a controlled, known deformation which can be compressive, tensile or zero.