A laser includes a traveling wave laser cavity with an active section, a pulse stretcher, and a pulse compressor. The pulse stretcher is coupled to the waveguide before the active section and the pulse compressor is coupled to the waveguide after the active section.

Provided is a distributed Bragg reflector tunable laser diode including a substrate provided with a gain section having an active waveguide from which a gain of laser light is obtained and a distributed reflector section having a passive waveguide connected to the active waveguide, wherein the distributed reflector section includes gratings disposed on or under the passive waveguide, a current injection electrode disposed on the passive waveguide and configured to provide a current into the passive waveguide to electrically tune a wavelength of the laser light, and a heater electrode disposed on the current injection electrode and configured to heat the passive waveguide to thermally tune the wavelength of the laser light, wherein the gratings, the current injection electrode, and the heater electrode vertically overlap each other.

A distributed reflector (DR) laser may include a distributed feedback (DFB) region and a distributed Bragg reflector (DBR). The DFB region may have a length in a range from 30 micrometers (m) to 100 m and may include a DFB grating with a first kappa in a range from 100 cm.sup.1 to 150 cm.sup.1. The DBR region may be coupled end to end with the DFB region and may have a length in a range from 30-300 m. The DBR region may include a DBR grating with a second kappa in a range from 150 cm.sup.1 to 200 cm.sup.1. The DR laser may additionally include a lasing mode and a p-p resonance frequency. The lasing mode may be at a long wavelength side of a peak of a DBR reflection profile of the DBR region. The p-p resonance frequency may be less than or equal to 70 GHz.

Provided is a distributed Bragg reflector tunable laser diode including a substrate provided with a gain section having an active waveguide from which a gain of laser light is obtained and a distributed reflector section having a passive waveguide connected to the active waveguide, wherein the distributed reflector section includes gratings disposed on or under the passive waveguide, a current injection electrode disposed on the passive waveguide and configured to provide a current into the passive waveguide to electrically tune a wavelength of the laser light, and a heater electrode disposed on the current injection electrode and configured to heat the passive waveguide to thermally tune the wavelength of the laser light, wherein the gratings, the current injection electrode, and the heater electrode vertically overlap each other.

A semiconductor monolithic transmitter photonic integrated circuit (TxPIC) comprises two different situations, either at least one signal channel in the PIC having a modulated source with the channel also extended to include at least one additional element or a plurality of modulated sources comprising N signal channels in the PIC of different transmission wavelengths, where N is equal to or greater than two (2), which may also approximate emission wavelengths along a standardized wavelength grid. In these two different situations, a common active region for such modulated sources and additional channel elements is identified as an extended identical active layer (EIAL), as it extends from a single modulated source to such additional channel elements in the same channel and/or extends to additional modulated sources in separate channels where the number of such channels is N equal to two or greater. The emission wavelength of laser sources in the modulated sources have different positively detuned offsets of the laser emission wavelength relative to the laser active region wavelength, i.e., (.sub.L,i.sub.PL,L,j>0), and their emission wavelengths form a wavelength grid which may substantially conform to a standardized wavelength grid, such as the ITU grid. These laser sources in the modulated sources with an EIAL are preferentially detuned in the range, for example, of about 20 nm to about 70 nm, preferentially from about 25 nm to about 50 nm, from the active region wavelength of the modulated sources.

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.

Laser diode comprises an active layer; a waveguiding region at least partially surrounding the active layer; a rear facet; a front facet designed for decoupling laser radiation, wherein the active layer extends at least partially along a first axis (X) between the rear facet and the front facet; and a grid operatively connected to the waveguiding region, wherein the grid comprises a plurality of webs and trenches designed such that an average increase of a coupling parameter P for the plurality of trenches along the grid is non-zero, wherein the coupling parameter P of a trench is defined by the formula, wherein dres is a distance of the trench to the active layer, w is a width of the trench and n is the refractive index difference between a refractive index of the trench and a refractive index of a material surrounding the trench.

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 includes: a waveguide structure including, in order, a first semiconductor layer, an active layer, and a second semiconductor layer; a p-type semiconductor layer disposed in contact with one side surface of the active layer; an n-type semiconductor layer disposed in contact with the other side surface of the active layer; a waveguide layer optically coupled to the active layer in a waveguide direction; a first diffraction grating disposed on either one of a lower surface of the first semiconductor layer, an upper surface of the second semiconductor layer, and a side surface of the active layer; a second diffraction grating disposed on either one of a lower surface and an upper surface of the waveguide layer; and a refractive index control unit for changing a refractive index of the waveguide layer. The semiconductor laser can achieve a good high-temperature operation with a simple configuration.

A surface emitting laser includes a lower reflector, an active layer, a gap portion, and an upper reflector, which are arranged in that order, and a driving unit. The surface emitting laser is capable of varying a wavelength of emitted light by changing a distance between the upper and lower reflectors. The driving unit moves one of the upper and lower reflectors in an optical axis direction of the emitted light. When .sub.g is a wavelength at which a gain at a time of laser oscillation of the active layer is at a maximum, .sub.0 is a center wavelength of the emitted light, and .sub.r is a wavelength at which a reflectance of one of the upper and lower reflectors from which the light is emitted is at a maximum, .sub.r <.sub.0 <.sub.g or .sub.g <.sub.0 <.sub.r is satisfied.