A semiconductor optical device includes a substrate containing silicon and including terraces, a waveguide, and a diffraction grating in different regions in plan view; and a semiconductor device formed of a III-V compound semiconductor and having an optical gain, the semiconductor device being joined to the diffraction grating and the terraces and being in contact with an upper surface of the substrate. The waveguide is optically coupled to the diffraction grating in a direction in which the waveguide extends. The terraces are located on both sides of the waveguide and the diffraction grating in a direction crossing the direction in which the waveguide extends. The substrate has a groove between each of the terraces and the waveguide. The diffraction grating is continuously connected to the terraces in the direction crossing the direction in which the waveguide extends.

A method of characterizing a monolithic tunable mid-infrared laser including a heterogeneous quantum cascade active region together with a least first and a second tunable integrated distributed feedback gratings, the method including operating the laser while tuning the first grating through its full tuning range, while holding the reflectivity function of the second grating constant, then operating the laser while tuning the second grating through its full tuning range, while holding the reflectivity function of the first grating constant.

A synthesized grating is provided comprising a substrate/layer, and a plurality of alternating aperiodic non-uniform low and high index profiles on a surface of the substrate/layer defining a transmission/reflection spectrum for one of either single or multi-frequency operation of said grating in an optical cavity. A method is also provided for designing the synthesized grating, comprising determining a grating structure of given profiles through analysis of an optimized weighted sum and mapping the grating profile to said surface with the plurality of alternating non-uniform low and high index profiles. A distributed feedback laser is also provided having top, bottom and two sides, comprising a top electrode, a cladding layer disposed below the top electrode a bottom electrode, a substrate disposed above the bottom electrode, one of either an active or passive waveguide layer, a synthesized aperiodic grating layer providing distributed mirrors, and wherein the waveguide layer and synthesized aperiodic grating layer are disposed between said the substrate and cladding layer and are separated by a spacer layer.

The present disclosure provides optical devices and methods for forming the optical devices. In some embodiments, the optical devices include active and passive regions. The active regions may include gallium and nitrogen containing epitaxial material, and the passive regions may include waveguide structures. The active and passive regions may be arranged on a carrier wafer in an end-to-end configuration. In other embodiments, the optical devices include laser devices or gain regions and dielectric waveguides. The laser devices or gain regions may include gallium and nitrogen containing epitaxial material.

To provide a semiconductor laser with which a high light output characteristic and reduction in occurrence of a lateral high-order mode can be achieved, the semiconductor laser includes a diffraction grating layer including first and second refractive index regions. A mesa structure includes a first region having a first width and a second region having a second width wider than the first width. The first region includes a diffraction grating region in which the first and second refractive index regions for use in reflecting a light beam having a Bragg wavelength are alternately arranged at the same period. The second region includes a diffraction grating region and a non-diffraction grating region. The diffraction grating region of the first region and the diffraction grating region of the second region form a resonator. A normalized coupling coefficient of the first region is larger than a normalized coupling coefficient of the second region.

A distributed feedback (DFB) laser includes a planar substrate; a laser section; and a mirror section optically coupled to said laser section. The laser section includes a front facet, an active layer substantially parallel to the planar substrate but not coplanar with the planar substrate and configured to emit light through the front facet, and a first Bragg grating arranged in a planar layer substantially parallel to the active layer but not coplanar with the active layer and on a side of the active layer opposite to the planar substrate. The mirror section is optically coupled to the laser section, and includes a second Bragg grating configured to reflect light towards the front facet. The second Bragg grating is arranged in a planar layer that is coplanar with the active layer.

A tunable laser device comprises a multi-section distributed feedback (DFB) laser having a first Bragg section including a waveguide and a Bragg grating, a second Bragg section comprising a waveguide and a Bragg grating, and a phase section being longitudinally located between the first Bragg section and the second Bragg section. The phase section is made of a passive material, and each Bragg section has a first longitudinal end joining the phase section and a second longitudinal end opposed to the phase section. The Bragg grating of at least one Bragg section has a grating coupling coefficient which decreases from the first longitudinal end to the second longitudinal end of the at least one Bragg section.

A method for producing a quantum cascade laser includes the steps of forming a laser structure including a mesa structure and a buried region embedding the mesa structure; forming a mask on the laser structure, the mask including a first pattern that defines a /4 period distribution Bragg reflector structure and a second pattern that defines a 3/4 period distribution Bragg reflector structure; and forming a first distribution Bragg reflector structure, a second distribution Bragg reflector structure, and a semiconductor waveguide structure by dry-etching the laser structure through the mask, the semiconductor waveguide structure including the mesa structure that has first and second end facets. The first distribution Bragg reflector structure is optically coupled to the first end facet. The second distribution Bragg reflector structure is optically coupled to the second end facet. Here, denotes a value of an oscillation wavelength of the quantum cascade laser in vacuum.

An optical semiconductor apparatus includes: semiconductor laser devices having different emission wavelengths and grouped into at least a first group and a second group; and an arrayed waveguide grating connected to the semiconductor laser devices of the first and second groups and configured to combine laser light beams radiating from the semiconductor laser devices into a same point. The arrayed waveguide grating is configured to combine laser light beams from the semiconductor laser devices belonging to the first group into the same point by diffraction in a first diffraction order in the arrayed waveguide grating, and combine laser light beams from the semiconductor laser devices belonging to the second group into the same point by diffraction in a second diffraction order different from the first diffraction order, in the arrayed waveguide grating.

A distributed feedback (DFB) semiconductor laser assembly is disclosed. The DFB laser assembly includes a substrate extending along a longitudinal direction, a first electrode layer disposed on a first side surface thereof, an active region layer disposed on a second side surface thereof opposite the first side surface, and a spacer layer disposed on the active region layer. A ridge extends away from the active region layer and along the longitudinal direction. The DFB laser assembly also includes a grating layer integrated between the active region layer and the ridge, the grating layer including a plurality of sampled gratings along the longitudinal direction, and a second electrode layer electrically coupled to the first electrode layer, the second electrode layer comprising independent electrode sections disposed on the top ridge surface and each ridge side surface.