Embodiments of the present invention include an apparatus for generating laser radiation with a semiconductor substrate, an intermediate layer arranged on the semiconductor substrate, and a Lateral Current Injection (LCI) laser arrangement arranged on the intermediate layer, wherein the intermediate layer includes a cavity extending at least under a laser strip of the LCI laser arrangement.

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.

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 non-etched gap is introduced along the length of an integrated Bragg grating with etched grooves such that the coupling coefficient, K, of the grating is reduced by the non-etched gap. In this way, multiple grating K values may be defined within a photonic integrated circuit using a single lithography and etch step. Additionally, the non-etched gap width may be varied along the length of a single grating to implement a chirped grating.

Provided is a surface emitting quantum cascade laser, including: semiconductor layers other than a laser active layer and the laser active layer; and a square-lattice or rectangular-lattice photonic crystal on the laser active layer, wherein a unit lattice of the square-lattice or rectangular-lattice photonic crystal is made of a composition A, and a composition B having a refractive index different from a refractive index of the composition A, and wherein the composition A is a compound semiconductor composition or metal composition, the composition B is a compound semiconductor composition, and the unit lattice of the square-lattice or rectangular-lattice photonic crystal has the following structure: a columnar structure body having a pentagonal bottom face and being made of the composition B is provided in a central part of the columnar structure body having the square or rectangular bottom face and being made of the composition A.

A semiconductor optical device includes a substrate having an optical waveguide, a gain section formed of a compound semiconductor having an optical gain and bonded to an upper surface of the substrate, the gain section having a first mesa, and a first wiring line electrically connected to the gain section. The first mesa of the gain section is optically coupled to the optical waveguide. The substrate includes a first layer, a second layer, and a third layer. The first layer has a higher thermal conductivity than the second layer. The second layer is stacked on the first layer. The third layer is stacked on the second layer. A recess provided in the substrate extends through the third layer to the second layer in the thickness direction. The first wiring line extends from the first mesa of the gain section to the recess.

An aspect of the present disclosure includes a direct modulated laser (DML) with a dielectric current confinement ridge waveguide (RWG) structure. The DML comprises a substrate, one or more layers of material disposed on the substrate to provide a multi quantum well (MQW), first and second insulation/dielectric structures disposed on opposite sides of the MQW, and one or more layers of material disposed on the MQW to provide a mesa structure for receiving a driving current. The mesa structure is preferably disposed between the first and second insulation structures to provide a dielectric current confinement (RWG) structure. The mesa structure further preferably includes an overall width that is greater than the overall width than the active region of the DML that provides the MQW.

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.

There are included: a second semiconductor layer of a second conduction-type formed to be on and in contact with the active layer; and a third semiconductor layer of a second conduction-type formed on the second semiconductor layer, the third semiconductor layer is arranged above a formation region of the active layer, a bottom surface of the third semiconductor layer is arranged in the formation region of the active layer, and a width of the third semiconductor layer, on the active layer side, in a direction perpendicular to a waveguide direction and parallel to a plane of a substrate is set to be smaller than a width of the active layer in the same direction.

A photonic integrated circuit may include a silicon layer including a waveguide and at least one other photonic component. The photonic integrated circuit may also include a first insulating region arranged above a first side of the silicon layer and encapsulating at least one metallization level, a second insulating region arranged above a second side of the silicon layer and encapsulating at least one gain medium of a laser source optically coupled to the waveguide.