Provided here are: a mesa strip which has an n-type cladding layer, an active layer and a p-type cladding layer that are stacked sequentially on a surface of an n-type substrate; Fe-doped semi-insulating layers which are embedded along both sides of the mesa stripe, each up to a height higher than the mesa stripe; n-type blocking layers which are stacked on respective surfaces of the Fe-doped semi-insulating layers located on the both sides of the mesa stripe, and which are spaced apart from each other with an interval that is a space corresponding to a central portion of the active layer and is thus narrower than the active layer; p-type cladding layers which are formed on back surfaces of respective mesa-stripe-side end portions of the n-type blocking layers; and a p-type cladding layer which buries a top of the mesa stripe, the p-type cladding layers and the n-type blocking layers.

Disclosed is an epitaxial substrate with a 2D material interposer on a surface of a polycrystalline substrate. The ultra-thin 2D material interposer is grown by van der Waals epitaxy. The lattice constant of a surface layer of the ultra-thin 2D material interposer and the coefficient of thermal expansion of the substrate base are highly fit with those of AlGaN or GaN. The ultra-thin 2D material interposer is of a single-layer structure or a composite-layer structure. An AlGaN or GaN single crystalline epitaxial layer is grown on the ultra-thin 2D material interposer by virtue of the van der Waals epitaxy. Therefore, the large-size substrate may be manufactured with far lower costs than related single crystal wafers.

A communication module includes a laser driving unit (LDU) and one or more multifunction illumination units. The one or more multifunction illumination units are be coupled to the LDU with an electrical connection and configured to transmit both electrical power and data.

Provided is a nitride semiconductor laser element which includes: a stacked structure including a plurality of semiconductor layers including a light emitting layer, the stacked structure including a pair of resonator end faces located on opposite ends; and a protective film including a dielectric body and disposed on at least one of the pair of resonator end faces. The protective film includes a first protective film (a first emission surface protective film), a second protective film (a second emission surface protective film), and a third protective film (a third emission surface protective film) disposed in stated order above the stacked structure. The first protective film is amorphous, the second protective film is crystalline, and the third protective film is amorphous.

An optical device includes: a substrate having a first surface, and a second surface opposite of the first surface; a plurality of surface emitting laser elements provided on the first surface of the substrate and configured to emit light in a direction intersecting the first surface; a plurality of optical elements disposed on the second surface so as to respectively correspond to the plurality of surface emitting laser elements; and an anti-reflection structure between the substrate and the plurality of optical elements.

A semiconductor laser diode is disclosed. In an embodiment a semiconductor laser diode includes a first resonator and a second resonator, the first and second resonators having parallel resonator directions along a longitudinal direction and being monolithically integrated into the semiconductor laser diode, wherein the first resonator includes at least a part of a semiconductor layer sequence having an active layer and an active region configured to be electrically pumped to generate a first light, wherein the longitudinal direction is parallel to a main extension plane of the active layer, and wherein the second resonator has an active region with a laser-active material configured to be optically pumped by at least a part of the first light to produce a second light which is partially emitted outwards from the second resonator.

Narrow-optical linewidth laser generation devices and methods for generating a narrow-optical linewidth laser beam are provided. One narrow-optical linewidth laser generation devie includes a single-wavelength mirror or multiwavelength mirror (for comb lasers) formed from one or more optical ring resonators coupled with an optical splitter. The optical splitter may in turn be coupled with a quantum dot optical amplifier (QDOA), itself coupled with a phase-tuner. The phase tuner may be further coupled with a broadband mirror. The narrow-optical linewidth laser beam is generated by using a long laser cavity and additionally by using an integrated optical feedback.

Narrow-optical linewidth laser generation devices and methods for generating a narrow-optical linewidth laser beam are provided. One narrow-optical linewidth laser generation devie includes a single-wavelength mirror or multiwavelength mirror (for comb lasers) formed from one or more optical ring resonators coupled with an optical splitter. The optical splitter may in turn be coupled with a quantum dot optical amplifier (QDOA), itself coupled with a phase-tuner. The phase tuner may be further coupled with a broadband mirror. The narrow-optical linewidth laser beam is generated by using a long laser cavity and additionally by using an integrated optical feedback.

An optical semiconductor device outputting a predetermined wavelength of laser light includes a quantum well active layer positioned between a p-type cladding layer and an n-type cladding layer in thickness direction. The optical semiconductor device includes a separate confinement heterostructure layer positioned between the quantum well active layer and the n-type cladding layer. The optical semiconductor device further includes an electric-field-distribution-control layer positioned between the separate confinement heterostructure layer and the n-type cladding layer and configured by at least two semiconductor layers having band gap energy greater than band gap energy of a barrier layer constituting the quantum well active layer. The quantum well active layer is doped with 0.3 to 1×10.sup.18/cm.sup.3 of n-type impurity.

A photonic crystal surface-emitting laser includes a substrate, an n-type cladding layer, an active layer, an index matching layer and a photonic crystal structure. The n-type cladding layer is disposed over the substrate. The active layer is disposed over the n-type cladding layer. The index matching layer is disposed over the n-type cladding layer and is arranged around the active layer. The index matching layer is electrically insulating, and an effective refractive index of the index matching layer is substantially identical to an effective refractive index of the active layer. The photonic crystal structure is disposed over the active layer and the index matching layer.