A laser system includes an edge emitting semiconductor laser, and an optical fiber, wherein the laser emits one or more laser beams coupled into the optical fiber and the laser includes a semiconductor body including a waveguide region that includes first and second waveguide layers and an active layer arranged between the first and second waveguide layers and generates laser radiation, the waveguide region is arranged between first and second cladding layers disposed downstream of the waveguide region, a phase structure is formed in the semiconductor body, includes a cutout extending from a top side of the semiconductor body into the second cladding layer, at least one first intermediate layer composed of a semiconductor material different from the material of the second cladding layer is embedded therein, and the cutout extends from the top side of the semiconductor body at least partly into the first intermediate layer.

The coordinates of an unit configuration region R11 is (X1, Y1), and the coordinates of an unit configuration region Rmn is (Xm, Yn) (m and n are natural numbers). Rotation angles with respect to a center of apexes of an isosceles triangle are different according to coordinates, and at least three different rotation angles are contained in all of the photonic crystal layer.

An improved longwave infrared quantum cascade laser. The improvement includes a strained In.sub.xGa.sub.1-xAs/Al.sub.yIn.sub.1-yAs composition, with x and y each between 0.53 and 1, an active region emitting at a wavelength equal to or greater than 8 m, an energy spacing E.sub.54 equal to or greater than 50 meV, an energy spacing E.sub.C4 equal to or greater than 250 meV, and an optical waveguide with a cladding layer on each side of the active region. Each cladding layer has a doping level of about 2.Math.10.sup.16 cm.sup.3. The optical waveguide also has a top InP layer with a doping level of about 5.Math.10.sup.16 cm.sup.3 and a bottom InP layer with a doping level of about 510.sup.16 cm.sup.3. Additionally, the optical waveguide has a plasmon layer with a doping level of about 8.Math.10.sup.18 cm.sup.3.

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; 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.

Photonic integrated circuits (PICs) are based on quantum cascade (QC) structures. In embodiment methods and corresponding devices, a QC layer in a wave confinement region of an integrated multi-layer semiconductor structure capable of producing optical gain is depleted of free charge carriers to create a low-loss optical wave confinement region in a portion of the structure. Ion implantation may be used to create energetically deep trap levels to trap free charge carriers. Other embodiments include modifying a region of a passive, depleted QC structure to produce an active region capable of optical gain. Gain or loss may also be modified by partially depleting or enhancing free charge carrier density. QC lasers and amplifiers may be integrated monolithically with each other or with passive waveguides and other passive devices in a self-aligned manner. Embodiments overcome challenges of high cost, complex fabrication, and coupling loss involved with material re-growth methods.

A quantum cascade laser is configured with a semiconductor substrate, and an active layer provided on a first surface of the substrate and having a multistage lamination of unit laminate structures each of which includes an emission layer and an injection layer. The active layer is configured to be capable of generating first pump light of a frequency .sub.1 and second pump light of a frequency .sub.2, and to generate output light of a difference frequency by difference frequency generation. An external diffraction grating is provided constituting an external cavity for generating the first pump light and configured to be capable of changing the frequency .sub.1, outside an element structure portion including the active layer. Grooves respectively formed in a direction intersecting with a resonating direction are provided on a second surface of the substrate.

An optical device has a gallium and nitrogen containing substrate including a surface region and a strain control region, the strain control region being configured to maintain a quantum well region within a predetermined strain state. The device also has a plurality of quantum well regions overlying the strain control region.

A quantum cascade laser is configured with a semiconductor substrate, and an active layer provided on a first surface of the substrate and having a cascade structure in the form of a multistage lamination of unit laminate structures each of which includes an emission layer and an injection layer. The active layer is configured to be capable of generating first pump light of a frequency .sub.1 and second pump light of a frequency .sub.2 by intersubband emission transitions of electrons, and to generate output light of a difference frequency by difference frequency generation from the first pump light and the second pump light. Grooves respectively formed in a direction intersecting with a resonating direction in a laser cavity structure are provided on a second surface opposite to the first surface of the substrate.

An edge emitting semiconductor laser includes a semiconductor body including a waveguide region, the waveguide region including first and second waveguide layers and an active layer arranged between the first and second waveguide layers, that generates laser radiation; the waveguide region is arranged between a first and second cladding layers disposed downstream of the waveguide region; a phase structure for selection of lateral modes of the laser radiation emitted by the active layer, wherein the phase structure includes at least one cutout extending from a top side of the semiconductor body into the second cladding layer; at least one first intermediate layer composed of a semiconductor material different from that of the second cladding layer embedded into the second cladding layer; and the cutout at least partly extends from the top side into the first intermediate layer; the second cladding layer contains a first partial layer adjoining the waveguide region.

A method of growing III-nitride-based devices, such as light emitting diodes (LEDs) and laser diodes (LDs) on or above a strain relaxed template (SRT). The SRT uses a thin, thermally decomposed, InGaN underlayer, which is referred to as a decomposition layer (DL). Above the DL is a n-type GaN or low composition InGaN decomposition stop layer (DSL). A buffer layer comprising an n-type InGaN/GaN superlattice (SL) is then grown. For an LD structure. an n-type waveguide layer comprising a second n-type InGaN/GaN SL is then grown. followed by an active region, a p-type electron blocking layer (EBL), a p-type waveguide layer comprising a p-type InGaN/GaN SL, and p-type GaN or p-type InGaN layers. For an LED structure, the waveguide layers may be omitted. In this disclosure, AlGaN means Al.sub.xGa.sub.(1-x)N with 1x0 and InGaN means In.sub.xGa.sub.(1-x)N with 1x0.