Various designs of semiconductor lasers may comprise a waveguide having a front region that is configured to support a plurality of transverse laser cavity modes and a rear region that support only one transverse laser cavity mode. These front and rear regions may be disposed between front and rear reflectors and may provide optical gain. Some such designs may be useful for providing higher power single mode semiconductor lasers.

A light emitting device includes a substrate, a buffer layer, a first active layer, and a plurality of mesa regions. A portion of the first active layer includes a first electrical polarity. The plurality of mesa regions includes at least a portion of the first active layer, a light emitting region on the portion of the first active layer, and a second active layer on the light emitting region. A portion of the second active layer includes a second electrical polarity. The light emitting region is configured to emit light which has a target wavelength between 200 nm to 300 nm. A thickness of the light emitting region is a multiple of the target wavelength, and a dimension of the light emitting region parallel to the substrate is smaller than 10 times the target wavelength, such that the emitted light is confined to fewer than 10 transverse modes.

A surface-emitting laser, which is a ridge waveguide structure, including: a substrate, a first cladding layer, an active layer, a conductive layer, a second cladding layer; the Bragg gratings is etched on the surface of the ridge waveguide; the two upper electrodes are disposed on both sides of the ridge waveguide; two grooves are formed between the ridge waveguide and each of the two upper electrodes; the first waveguide cladding layer includes one or more current confinement regions; or a buried tunnel junction is formed in the second cladding layer for limiting current. The Bragg gratings comprise two first-order gratings and one second-order grating placed between two first-order gratings.

An optical semiconductor element including a semiconductor substrate, a first cladding layer of a first conductive type provided on the semiconductor substrate, an active layer provided on the first cladding layer, a second cladding layer of a second conductive type provided on the active layer, a first mesa constituted of a part of the first cladding layer, the active layer, and the second cladding layer, an auxiliary cladding layer of the second conductive type provided on the first mesa, a second mesa constituted of the auxiliary cladding layer, and a semi-insulating layer provided on the first cladding layer and on both sides of the first mesa and both sides of the second mesa, wherein a width of the second mesa is greater than a width of the first mesa.

A method for producing a semiconductor optical device includes the steps of bonding a semiconductor chip to an SOI substrate having a waveguide, the semiconductor chip having an optical gain and including a first cladding layer, a core layer, and a second cladding layer that contain III-V group compound semiconductors and are sequentially stacked in this order, forming a covered portion with a first insulating layer on the second cladding layer, etching partway in the thickness direction the second cladding layer exposed from the first insulating film, forming a second insulating film covering from the covered portion to a part of a remaining portion of the second cladding layer, and forming a first tapered portion that is disposed on the waveguide and tapered along the extending direction of the waveguide by etching the core layer and the second cladding layer exposed from the second insulating film.

A semiconductor optical amplifier integrated laser includes a semiconductor laser oscillator portion that oscillates laser light having a wavelength included in a gain band and a semiconductor optical amplifier portion that amplifies laser light output from the semiconductor laser oscillator portion. The semiconductor laser oscillator portion and the semiconductor optical amplifier portion have one common p-i-n structure, the common p-i-n structure includes an active layer, a cladding layer provided apart from the active layer, and a common functional layer formed in the cladding layer, and the common functional layer includes a first portion that reflects light having a wavelength within the gain band in the semiconductor laser oscillator portion and a second portion that transmits light having a wavelength within the gain band in the semiconductor optical amplifier portion.

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

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.

In one embodiment, a distributed feedback laser includes a laser comprising a waveguide, the waveguide having a variable width from a first end to a second end, the laser to generate optical energy of a plurality of lasing wavelengths. Other embodiments are described and claimed.

A semiconductor laser element includes: an n-type cladding layer disposed above an n-type semiconductor substrate (a chip-like substrate); an active layer disposed above the n-type cladding layer; and a p-type cladding layer disposed above the active layer, in which the active layer includes a well layer and a barrier layer, an energy band gap of the barrier layer is larger than an energy band gap of the n-type cladding layer, and a refractive index of the barrier layer is higher than a refractive index of the n-type cladding layer.