A manufacturing method for an optical semiconductor device includes: forming a first semiconductor layer; forming a first mask pattern on the first semiconductor layer in a first area where an electro absorption type modulator is formed; forming an unevenness along the first direction on the first semiconductor layer; forming a second semiconductor layer on the unevenness; and forming an optical waveguide layer on the second semiconductor layer. The first mask pattern includes a first pattern in the first area and a second pattern in a second area where a DFB laser is formed, the first pattern including a first opening pattern and a first cover pattern, and the second pattern including a second opening pattern and a second cover pattern, and a ratio of the first opening pattern to the first cover pattern is different from that of the second opening pattern to the second cover pattern.

According to various embodiments, there is provided an optical device including a first waveguide configured to guide a light wave along a longitudinal axis; a first grating at least partially formed in the first waveguide, the first grating arranged away from the longitudinal axis in a first direction; and a second grating at least partially formed in the first waveguide, the second grating arranged away from the longitudinal axis in a second direction; wherein the second direction is different from the first direction.

A semiconductor laser device having a diffraction grating is disclosed. The semiconductor laser device comprises a first diffraction grating provided on a substrate, a second diffraction grating continuous to one end of the first diffraction grating along an optical waveguide direction, and an active layer provided above the first diffraction grating. The second diffraction grating has a pitch 1.05 times or greater, or 0.95 times or smaller of the pitch of the first diffraction grating.

A quantum cascade laser includes a semiconductor substrate and an active layer having a cascade structure, in which unit layered bodies, each composed of a quantum well light emitting layer and an injection layer, are stacked, wherein the unit layered body has a subband level structure having an upper laser level, a lower laser level, and a relaxation miniband composed of at least two energy levels with an energy spacing smaller than the energy difference (E.sub.UL) between the upper laser level and the lower laser level, the energy width of the relaxation miniband is smaller than the energy (E.sub.LO−E.sub.UL) obtained by subtracting the energy difference (E.sub.UL) from the energy (E.sub.LO) of longitudinal optical phonons, and electrons subjected to the intersubband transition are relaxed in the relaxation miniband and are injected into a quantum well light emitting layer in a subsequent unit layered body.

A semiconductor stack includes a first-conductivity-type layer, a quantum well structure, and a second-conductivity-type layer. The first-conductivity-type layer, the quantum well structure, and the second-conductivity-type layer are stacked in this order. The quantum well structure includes a first semiconductor layer, a second semiconductor layer, and a third semiconductor layer. In the first semiconductor layer and the third semiconductor layer, compositions of the first semiconductor layer and the third semiconductor layer are changed such that a bandgap decreases toward the second semiconductor layer. Transition of an electron is possible between a conduction band of each of the first semiconductor layer and the third semiconductor layer and a valence band of the second semiconductor layer.

The present disclosure describes broadband optical emission sources that include a stack of semiconductor layers, wherein each of the semiconductor layers is operable to emit light of a different respective wavelength; a light source operable to provide optical pumping for stimulated photon emission from the stack; wherein the semiconductor layers are disposed sequentially in the stack such that a first one of the semiconductor layers is closest to the light source and a last one of the semiconductor layers is furthest from the light source, and wherein each particular one of the semiconductor layers is at least partially transparent to the light generated by the other semiconductor layers that are closer to the light source than the particular semiconductor layer. The disclosure also describes various spectrometers that include a broadband optical emission device, and optionally include a tuneable wavelength filter operable to allow a selected wavelength or narrow range of wavelengths to pass through.

A semiconductor device manufacturing system includes: a PL evaluation apparatus that evaluates wavelengths of photoluminescent light produced by individual optical modulators on a single semiconductor wafer; an electron beam drawing apparatus that draws patterns of diffraction gratings of laser sections that adjoin respective optical modulators on the wafer; and a calculation section that receives the wavelengths of the photoluminescent light from the PL evaluation apparatus, calculates densities of respective diffraction gratings so that differences between the wavelengths of the photoluminescent light and oscillating wavelengths of the laser sections become a constant, and sends the densities calculated to the electron beam drawing apparatus for drawing respective diffraction grating patterns on the respective laser sections.

To provide a semiconductor optical device with device resistance reduced for optical communication. The semiconductor optical device includes an active layer (306) for emitting light through recombination of an electron and a hole; a diffraction grating (309) having a pitch defined in accordance with an output wavelength of the light emitted; a first semiconductor layer (311) including at least Al, made of In and group-V compound, and formed on the diffraction grating; and a second semiconductor layer (307) including Mg, made of In and group-V compound, and formed on the first semiconductor layer (311).

A quantum cascade laser includes a substrate including first and second regions arranged along a first axis; a stacked semiconductor layer disposed in the second region, the stacked semiconductor layer having an end facet located on a boundary between the first and second regions, the stacked semiconductor layer including a core layer and a cladding layer that are exposed at the end facet thereof; and a distributed Bragg reflection structure disposed in the first region, the distributed Bragg reflection structure including a semiconductor wall and a covering semiconductor wall that covers the end facet of the stacked semiconductor layer. The semiconductor wall and the covering semiconductor wall are made of a single semiconductor material. The semiconductor wall has first and second side surfaces. The covering semiconductor wall has an end facet that is located away from the first and second side surfaces of the semiconductor wall.

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 θ.sub.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 ω.sub.1, light of a second frequency ω.sub.2, and light of a third frequency ω.sub.THz, wherein ω.sub.THz=ω.sub.1−ω.sub.2; an upper cladding layer; and a lower cladding layer. The device comprises a distributed feedback grating layer configured to provide optical feedback for one or both of the light of the first frequency ω.sub.1 and the light of the second frequency ω.sub.2 and to produce lasing at one or both of the first frequency ω.sub.1 and the second frequency ω.sub.2, thereby resulting in laser emission at the third frequency ω.sub.THz at a Cherenkov angle θ.sub.THz through the bottom surface of the waveguide structure into the substrate and exiting the substrate through the exit facet. The device comprises a high-reflectivity coating on the front facet of the waveguide structure.