A semiconductor light emitting element includes an optical waveguide having a first and second waveguide provided with a width that allows propagation of light in a second-order mode or higher and a multimode optical interference waveguide provided with a wider width than the first and second waveguide and arranged at a position therebetween. The semiconductor light emitting element further includes a first optical loss layer facing the first waveguide in an active-layer crossing direction for causing a loss of light that is propagating in the first waveguide in the second-order mode or higher and a second optical loss layer facing the second waveguide in an active-layer crossing direction for causing a loss of light that is propagating in the second waveguide in the second-order mode or higher, the active-layer crossing direction being orthogonal to a surface of an active layer.

A semiconductor laser element includes: a substrate; a first semiconductor layer; a light emission layer; a second semiconductor layer; and a groove part formed at least at the substrate and the first semiconductor layer. The second semiconductor layer has a ridge part for guiding laser light generated in the light emission layer. A width of the ridge part cyclically changes in accordance with a position in a waveguiding direction of the ridge part. An angle between a side face of the ridge part and the waveguiding direction is larger than a limit angle defined by an effective refractive index on each of an inner side of the ridge part and an outer side of the ridge part. The groove part is disposed on the outer side of the side face at least where the width of ridge part is small.

A semiconductor laser is provided with: an active layer that excites a transverse electric (TE) mode and a transverse magnetic (TM) mode of light and constitutes at least a part of a resonator guiding the TE mode and the TM mode of light; and a diffraction grating as a frequency difference setting structure that sets the difference in oscillation frequency between the TE mode and the TM mode of light higher than a relaxation-oscillation frequency

In a semiconductor laser device, a semiconductor layer includes a first groove formed on both sides of a ridge, a pair of second recesses facing each other and between which the ridge is interposed on a side of a light emitting surface, and a pair of third grooves in parallel to the first groove from the light emitting surface and interposing the ridge therebetween.

A semiconductor laser device includes: a first conductivity side semiconductor layer, an active layer; and a second conductivity side semiconductor layer. The second conductivity side semiconductor layer includes a first semiconductor layer and a second semiconductor layer, the first semiconductor layer being closer to the active layer than the second semiconductor layer is. The second semiconductor layer defines a width of a current injection region for injecting current into an optical waveguide. The current injection region includes a width varying region in which a width varies. S1>S2, where S1 denotes a width of the width varying region on a front end face side, and S2 denotes a width of the width varying region on a rear end face side.

The present disclosure discloses a narrow-linewidth laser. The narrow-linewidth laser comprises a passive ring waveguide, a first passive input/output waveguide which is coupled with the passive ring waveguide, a gain wavelength-selection unit which is used for providing gain for the whole laser and is configured to be capable of selecting the light with a specific wavelength to be coupled into the passive ring waveguide, and a second passive input/output waveguide which is coupled with the passive ring waveguide in order to output lasing light from the laser. The narrow-linewidth semiconductor laser provided by the present disclosure has a simple structure and does not have butt-joint coupling loss between a gain region and a waveguide external cavity region. There is no a linewidth limitation caused by butt-coupling loss in such semiconductor lasers. Moreover, because of the integral formation semiconductor technique, the laser should have low cost, higher stability and reliability, and higher resistance to severe environment. Furthermore, based on a loss compensation structure, a ring external cavity of the laser can work in a critical coupling state under different coupling coefficients. Therefore, the laser with a narrow linewidth and a high side-mode suppression ratio should be achieved.

A VCSEL can include: an active region configured to emit light; a blocking region over or under the active region, the blocking region defining a plurality of channels therein; a plurality of conductive channel cores in the plurality of channels of the blocking region, wherein the plurality of conductive channel cores and blocking region form an isolation region; a top electrical contact; and a bottom electrical contact electrically coupled with the top electrical contact through the active region and plurality of conductive channel cores. At least one conductive channel core is a light emitter, and others can be spare light emitters, photodiodes, modulators, and combinations thereof. A waveguide can optically couple two or more of the conductive channel cores. In some aspects, the plurality of conductive channel cores are optically coupled to form a common light emitter that emits light (e.g., single mode) from the plurality of conductive channel cores.

A semiconductor laser device includes an optical waveguide that extends toward a first end of the semiconductor laser device. The optical waveguide includes a first clad layer, an active layer, a second clad layer, and an electrode layer in this order. A reflecting surface, which has a dielectric film and a metal film in this order from the active layer, crosses the active layer at a second end of the optical waveguide.

Methods for designing a mode-selective optical device including one or more optical interfaces defining an optical cavity include: defining a loss function within a simulation space encompassing the optical device, the loss function corresponding to an electromagnetic field having an operative wavelength within the optical device resulting from an interaction between an input electromagnetic field at the operative wavelength and the one or more optical interfaces of the optical device; defining an initial structure for each of the one or more optical interfaces, each initial structure being defined using a plurality of voxels; determining values for at least one structural parameter and/or at least one functional parameter of the one or more optical interfaces by solving Maxwell's equations; and defining a final structure of the one or more optical interfaces based on the values for the one or more structural and/or functional parameters.

A grating emitter method and system for modulating the polarization of an optical beam, such as one for transmission through free-space or use in an atomic clock.