A wavelength-variable laser 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; a separate confinement heterostructure layer positioned between the quantum well active layer and the n-type cladding layer; and 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.

A light-emitting device includes a semiconductor laser element, a wavelength conversion member, and a package. The wavelength conversion member includes a wavelength conversion portion and a reflective portion as in the specification. The wavelength conversion portion includes a light incident surface and a light-emitting surface as in the specification. The package includes a disposition region as in the specification. The wavelength conversion member is disposed at a position away in a first direction from a position at which the semiconductor laser element is disposed. In a plan view perpendicular to the light-emitting surface, the light-emitting surface has a shape that has a first region as in the specification, and a region of at least 80% or more of the light incident surface overlaps an imaginary line that passes through a point of the light-emitting surface closest to the semiconductor laser element and that is parallel to the second direction.

A light emitter includes a substrate including a first surface, a cladding on the first surface of the substrate, a core inside the cladding, a lid on the cladding, a first light-emitting element inside an element sealing area on the first surface, a second light-emitting element inside the element sealing area, a first light-receiving element inside the element sealing area, and a second light-receiving element inside the element sealing area. A first light-receiving surface of the first light-receiving element faces the lid, and a second light-receiving surface of the second light-receiving element faces the lid.

A VCSEG-DFB laser, fully compatible with MGVI design and manufacturing methodologies, for single growth monolithic integration in multi-functional PICs is presented. It comprises a laser PIN structure, in mesa form, etched from upper emitter layer top surface through the active, presumably MQW, gain region, down to the top surface of the lower emitter. Lower electrical contacts sit adjacent the mesa disposed on the lower emitter layer with upper strip contacts disposed atop the upper emitter layer on the mesa top. An SEG is defined/etched from mesa top surface, between the upper strip contacts, through upper emitter layer down to or into the SCH layers. Vertical confinement is provided by the SCH structure and the lateral profile in the bottom portion of the mesa provides lateral confinement. The guided mode interacts with the SEG by the vertical tail penetrating the SEG and evanescent field coupling to the SEG.

A two-dimensional photonic crystal laser with transparent conductive cladding layer is provided. The two-dimensional photonic crystal region through the etching process is composed by multiple periodic air-holes with proper duty cycle. Then, the transparent conductive oxide layer is directly deposited on the top of the entire two-dimensional photonic crystal structure to cover the entire two-dimensional photonic crystal structure in order to form a current spreading layer. The configuration and the process condition of transparent conductive oxide layer are optimized to provide uniform current spreading path and the transparency. In addition to simplifying the whole fabrication process, the optical confinement is improved and the maximum gain to optical feedback is obtained. Overall, low threshold, small divergence angle and high quality laser output is achieved to satisfy the requirements for next-generation light sources.

A VCSEG-DFB laser, fully compatible with MGVI design and manufacturing methodologies, for single growth monolithic integration in multi-functional PICs is presented. It comprises a laser PIN structure, in mesa form, etched from upper emitter layer top surface through the active, presumably MQW, gain region, down to the top surface of the lower emitter. Lower electrical contacts sit adjacent the mesa disposed on the lower emitter layer with upper strip contacts disposed atop the upper emitter layer on the mesa top. An SEG is defined/etched from mesa top surface, between the upper strip contacts, through upper emitter layer down to or into the SCH layers. Vertical confinement is provided by the SCH structure and the lateral profile in the bottom portion of the mesa provides lateral confinement. The guided mode interacts with the SEG by the vertical tail penetrating the SEG and evanescent field coupling to the SEG.

A two-dimensional photonic crystal laser with transparent conductive cladding layer is provided. The two-dimensional photonic crystal region through the etching process is composed by multiple periodic air-holes with proper duty cycle. Then, the transparent conductive oxide layer is directly deposited on the top of the entire two-dimensional photonic crystal structure to cover the entire two-dimensional photonic crystal structure in order to form a current spreading layer. The configuration and the process condition of transparent conductive oxide layer are optimized to provide uniform current spreading path and the transparency. In addition to simplifying the whole fabrication process, the optical confinement is improved and the maximum gain to optical feedback is obtained. Overall, low threshold, small divergence angle and high quality laser output is achieved to satisfy the requirements for next-generation light sources.

A semiconductor laser device includes a first cladding including gallium nitride (GaN) on a substrate, a light waveguide on the first cladding, a first contact pattern, a first SCH pattern, a first active pattern, a second SCH pattern, a second cladding and a second contact pattern sequentially stacked on the light waveguide, and first and second electrodes on the first and second contact patterns, respectively.

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.LOE.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.

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 optical semiconductor device is applied to a ridge-stripe type laser.