A semiconductor light-emitting device including a light-emitting layer, a first N-type waveguide layer and a plurality of semiconductor layers is provided. The light light-emitting layer has a first side and a second side opposite to the first side. The first N-type waveguide layer is disposed at the first side, and the semiconductor layers are disposed at the second side. The semiconductor layers include at least one P-type semiconductor layer and a plurality of N-type semiconductor layers, and a quantity of the N-type semiconductor layers is more than a quantity of the at least one P-type semiconductor layer.

A light emitting device is provided that makes it possible to reduce absorption of light by an electrode. The light emitting device includes a substrate, and a laminated structure provided to the substrate, wherein the laminated structure includes a first semiconductor layer, a second semiconductor layer different in conductivity type from the first semiconductor layer, and an active layer disposed between the first semiconductor layer and the second semiconductor layer, the first semiconductor layer is disposed between the substrate and the active layer, a recessed part is disposed at an opposite side to the substrate side of the laminated structure, the recessed part is provided with a low refractive-index part lower in refractive index than the second semiconductor layer, a depth of the recessed part is no larger than a distance between a surface at an opposite side to the substrate side of the laminated structure and the active layer, and an electrode is disposed at an opposite side to the substrate side of the laminated structure.

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 device comprising a silicon substrate on which is grown a <100 nm thick epilayer of AlAs or related compound, followed by a compound semiconductor other than GaN buffer layer. Further III-V compound semiconductor structures can be epitaxially grown on top. The AlAs epilayer reduces the formation and propagation of defects from the interface with the silicon, and so can improve the performance of an active structure grown on top.

An edge-emitting semiconductor laser diode chip 15 with mutually opposed front and back end facet mirrors 22, 24. First and second ridges 26.sub.1, 26.sub.2 extend between the chip end facets 22, 24 to define first and second waveguides in an active region layer. Low and high slope efficiency laser diodes are thus formed that are independently drivable by respective electrode pairs 21.sub.1, 23.sub.1 and 21.sub.2, 23.sub.2. The single chip 15 thus incorporates two laser diodes sharing a common heterostructure, one with low slope efficiency optimized for low power operation with good power stability against temperature variations and random threshold current fluctuations in the close-to-threshold power regime, and the other with high slope efficiency optimized for high wall plug efficiency operation at higher output powers when the chip is operating far above threshold.

An optical module includes a waveguide interposer and at least one light source unit. The waveguide interposer includes at least one input terminal, at least one waveguide channel, and at least one output terminal. The at least one input terminal is configured to receive laser light, and the at least one waveguide channel is coupled to the at least one input terminal and is configured to guide the laser light. Each light source unit is configured to output the laser light to a corresponding input terminal of the at least one input terminal.

A laser structure comprising a first photonic crystal surface emitting laser (PCSEL), a second PCSEL, and a coupling region that extends between the first PCSEL and the second PCSEL along a longitudinal axis and that is electrically controllable so as to be capable of coherently coupling the first PCSEL to the second PCSEL. Each PCSEL include an active layer, a photonic crystal, and a two-dimensional periodic array distributed in an array plane parallel to the longitudinal axis within the photonic crystal where the two-dimensional periodic array is formed of regions having a refractive index that is different to the surrounding photonic crystal.

An embodiment semiconductor optical device includes an optical waveguide including a core, and an active layer extending in the waveguide direction of the optical waveguide for a predetermined distance and arranged in a state in which the active layer can be optically coupled to the core. The core and the active layer are arranged in contact with each other. The core is formed of a material with a refractive index of about 1.5 to 2.2, such as SiN, for example. In addition, the core is formed to a thickness at which a higher-order mode appears. The higher-order mode is an E.sub.12 mode, for example.

A semiconductor optical integrated device in which a forward-bias optical device and a semiconductor laser are monolithically integrated on a semiconductor substrate, includes: a passive waveguide portion that is arranged between the forward-bias optical device and the semiconductor laser; and a ground electrode that is arrange on a lower surface of the semiconductor substrate. Further, the semiconductor laser includes a mirror having a length on a side closer to the forward-bias optical device, the forward-bias optical device includes a forward-bias optical-device electrode on a side opposite to a side in contact with the semiconductor substrate, the passive waveguide portion includes a passive waveguide electrode on a side opposite to a side in contact with the semiconductor substrate, and the passive waveguide electrode is electrically connected to the ground electrode.

A method for increasing the bandwidth of an electroabsorption modulator (EAM) includes the following steps. First, a plurality of p-i-n active waveguides for the EAM are defined on a p-i-n optical waveguide forming an EAM having a shorter p-i-n active waveguide length. Then, the bandwidth of the EAM can be increased. Second, the high-impedance transmission lines are used in series to connect the EAM sections to reduce the microwave reflection and then increase the device bandwidth. Finally, the impedance-controlled transmission lines for the signal input and output can not only reduce the parasitic effects resulting from packaging, but also reduce the microwave reflection resulting from the impedance mismatch at the device input and load.