The invention provides a distributed reflector (DR) semiconductor laser, comprising two cavity sections which are composed of a distributed feedback (DFB) section and a distributed Bragg reflector (DBR) section. The active region of the DR laser is formed of quantum dot (QD) layers and the two sections have separate electrodes. The QD layers in the DFB section provide optical gain, and the QD layers in the DBR section are biased just above transparent to provide a passive waveguide DBR.

A photonic element includes a bottom cladding, a top cladding and a first waveguide that is located between the bottom and top claddings. A first multi-wavelength grating is optically coupled with the first waveguide. The multi-wavelength grating is characterized by a grating strength that varies along a first axis based on a piecewise mathematical function. The first waveguide and the multi-wavelength grating collectively enable an output having a plurality of wavelengths.

Single-mode quantum cascade semiconductor lasers are provided. The lasers comprise a laser element, the laser element comprising a quantum cascade active layer; an upper cladding layer over the quantum cascade active layer; and a lower cladding layer under the quantum cascade active layer, wherein the quantum cascade active layer, the upper cladding layer and the lower cladding layer define a guided optical mode. The quantum cascade active layer and the upper and lower cladding layers are shaped in the form of a ridge structure having a front face, a back face opposite the front face, and a lasing face through which laser emission exits the ridge structure, the ridge structure configured such that the laser emission has a single-lobe, far-field beam pattern from the ridge structure comprising certain sections, including tapered sections, collateral sections, or both.

A semiconductor laser, an optical transmitter component, an optical line terminal, and an optical network unit. The semiconductor laser includes a substrate, a lower waveguide layer, a lower confining layer, a central layer, an upper confining layer, a grating layer, an upper waveguide layer, and an electrode layer that are sequentially formed on the substrate. The upper confining layer, the central layer, and the lower confining layer in a filtering region form a core layer of the filtering region. The grating layer in the filtering region includes a slanted grating. Thus, a modulation chirp and dispersion of a transmitted optical pulse can be reduced.

A distributed feedback laser (DFB) is a type of laser diode in which the active region of the device contains a periodically structured element or diffraction grating, which may include periodic changes in refractive index that cause reflection back into the laser cavity. Conventional DFB lasers used in optical networks may exploit either loss-modulated or index-modulated gratings. In the case of complex-coupling, index-modulated and loss-modulated gratings may be combined together.

Disclosed is a surface etched grating semiconductor laser with periodic pumping structure. The structure includes a lower doped dielectric layer, a multiple quantum well active layer, a ridge-shaped doped dielectric layer, periodic grating grooves formed on the ridge-shaped doped dielectric layer and a top electrical contact layer forming ohmic electrical contact with electrical contact regions between the grating grooves. Carriers are injected through the periodic electrical contact layer, flow through the electrical contact regions, spread laterally when reaching the bottom of the grating grooves, and then continue to spread to the multiple quantum well active layer. In a case of uniform distribution, a laser based on refractive index modulation is realized. In a case of non-uniform distribution, a laser with mixed modulation is realized by introducing additional gain modulation.