Abstract: A terahertz quantum cascade laser device is provided comprising a substrate having a top substrate surface, a bottom substrate surface, and an exit facet extending between the top substrate surface and the bottom substrate surface at an angle ?tap. The device comprises a waveguide structure having a top surface, a bottom surface, a front facet extending between the top surface and the bottom surface and positioned proximate to the exit facet, and a back facet extending between the top surface and the bottom surface and oppositely facing the front facet. The waveguide structure comprises a quantum cascade laser structure configured to generate light comprising light of a first frequency ?1, light of a second frequency ?2, and light of a third frequency ?THz, wherein ?THz=?1??2; an upper cladding layer; and a lower cladding layer.

Abstract: Semiconductor lasers comprise a substrate; an active layer configured to generate transverse magnetic (TM) polarized light under an electrical bias; an upper cladding layer; a lower cladding layer; and a distributed feedback (DFB) grating defined by the interface of a layer of metal and a layer of semiconductor under the layer of metal, the interface periodically corrugated in the longitudinal direction of the laser with a periodicity of ?DFB=m?/(2neff), wherein m>1. The DFB grating is configured such that loss of one or more antisymmetric longitudinal modes of the laser structure via absorption to the DFB grating is sufficiently maximized so as to produce lasing of a symmetric longitudinal mode of the laser with laser emission characterized by a single-lobe beam along each direction defined by the grating diffraction orders corresponding to emission away from the plane of the grating.

Abstract: Semiconductor lasers comprise a substrate; an active layer configured to generate transverse magnetic (TM) polarized light under an electrical bias; an upper cladding layer; a lower cladding layer; and a distributed feedback (DFB) grating defined by the interface of a layer of metal and a layer of semiconductor under the layer of metal, the interface periodically corrugated in the longitudinal direction of the laser with a periodicity of ?DFB=m?/(2neff), wherein m>1. The DFB grating is configured such that loss of one or more antisymmetric longitudinal modes of the laser structure via absorption to the DFB grating is sufficiently maximized so as to produce lasing of a symmetric longitudinal mode of the laser with laser emission characterized by a single-lobe beam along each direction defined by the grating diffraction orders corresponding to emission away from the plane of the grating.

Abstract: Semiconductor structures, quantum cascade structures and lasers including the structures are provided. The semiconductor structures include a substrate, a metamorphic buffer layer structure over the substrate, and a quantum cascade structure including a superlattice of quantum wells and barriers over the metamorphic buffer layer structure. The substrate may be GaAs and the quantum cascade structure may be an InGaAs/InAlAs superlattice, including one or more barriers of AlAs.

Abstract: Semiconductor structures, quantum cascade structures and lasers including the structures are provided. The semiconductor structures include a substrate, a metamorphic buffer layer structure over the substrate, and a quantum cascade structure including a superlattice of quantum wells and barriers over the metamorphic buffer layer structure. The substrate may be GaAs and the quantum cascade structure may be an InGaAs/InAlAs superlattice, including one or more barriers of AlAs.