A tunable laser, including: a gain section configured to provide an optical gain for lasing; a multi-channel splitter section configured to split an input signal into multiple outputs; and a multi-channel reflection section, the multi-channel reflection section including multiple arms of unequal lengths and configured to provide an optical feedback and a mode selection function for the laser to work. The gain section, the multi-channel splitter section, and the multi-channel reflection section are sequentially connected in that order. The facet of the gain section away from the multi-channel splitter section is an optical output facet of the laser. When arranging the multiple arms of the multi-channel reflection section in an order according to their lengths, length difference between adjacent arms are unequal. Facets of the multiple arms away from the multi-channel splitter section are coated with reflection films.

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 wavelength tunable silicon-on-insulator (SOI) laser comprising: a laser cavity including: a semiconductor gain medium having a front end and a back end, wherein a mirror of the laser cavity is located at the back end of the semiconductor gain medium; and a phase-tunable waveguide platform coupled to the front end of the semiconductor gain medium, the phase-tunable waveguide platform comprising: a first resonator and a second resonator; at least one resonator being a phase-tunable resonator; wherein the first resonator is any one of: an MMI device including a pair of reflective surfaces defining a resonator cavity therebetween such that the device is configured to act as a Fabry-Perot filter; a ring resonator; or a waveguide Fabry-Perot filter; and wherein the second resonator is any one of: an MMI device including a pair of reflective surfaces defining a resonator cavity therebetween such that the device is configured to act as a Fabry-Perot filter; a ring resonator; or a waveguide Fabry-Perot filter.

An optical source includes a semiconductor optical amplifier that provides an optical signal, and a photonic chip with first and second ring resonators that operate as Vernier rings. When the optical source is operated below a lasing threshold, one or more thermal-tuning mechanisms, which may be thermally coupled to the first ring resonator and/or the second ring resonator, may be adjusted to align resonances of the first ring resonator and the second ring resonator based on measured optical power on a shared optical waveguide that is optically coupled to the first and second ring resonators. Then, when the optical source is operated above the lasing threshold, a common thermal-tuning mechanism may be adjusted to lock the aligned resonances with an optical cavity mode of the optical source based on a measured optical power on an optical waveguide that is optically coupled to the first ring resonator.

An optical circuit capable of reducing a frequency variation of a light source caused by rotation is provided. The optical circuit includes a substrate, a laser light source formed on the substrate and including a first annular optical waveguide and a second annular optical waveguide that shares a part thereof with the first annular optical waveguide at one location, a first optical waveguide located on the substrate at a position separated from the laser light source and optically coupled to the laser light source, and a resonator optically coupled to the first optical waveguide.

The invention relates to a tunable laser, the tunable laser comprising a first waveguide, a second waveguide and a semiconductor layer being arranged to separate the first waveguide from the second waveguide. The first waveguide comprises a first coupling portion and an active portion for generating a laser signal. The second waveguide comprises a second coupling portion and a tuning portion for tuning the wavelength of the laser signal. The first coupling portion and the second coupling portion are configured to couple the laser signal between the first waveguide and the second waveguide through the semiconductor layer.

A quantum cascade laser (QCL) may include multiple branch waveguide regions having one or more laser cores providing optical gain at one or more output wavelengths, a stem waveguide region, and multiple couplers arranged to couple light from the plurality of branch waveguide regions to the stem waveguide region. Each of the couplers may include two or more curved waveguide regions having a continuously-varying radius of curvature providing that a fundamental transverse mode at the output wavelengths is dominant, and a coupler to combine light from the two or more curved waveguides and maintain dominance of the fundamental transverse mode at the output wavelengths. The fundamental transverse mode at the output wavelengths may be dominant in output light from the stem waveguide.

There is provided an external cavity laser, including: a photonic integrated platform including a gain chip providing a gain medium and at least one reflector chip, the photonic integrated platform including first and second functional layers made of different materials; a resonant cavity optically coupled to the gain medium and including a first and a second micro-ring resonators (MRR) in a Vernier configuration, the first MRR and second MRR extending within respective ones of the first and second functional layers made of different materials and having corresponding group indices, the first and second MRRs having different radii selected in view of said corresponding group indices; and a tuning mechanism for tuning a spectral response of at least one of the first and second MRR.

A semiconductor tunable ring laser including a laser cavity having a closed loop optical path, and an optical filter that is arranged within the laser cavity and configured as a transmission-type optical filter if the semiconductor tunable ring laser is in use. The optical filter includes a first MZI-based tunable frequency filter section including a first 22 MMI output splitter having an x/(100x) split ratio with x being unequal to 50. The first 22 MMI output splitter provides the laser cavity with an optical monitoring port that is presented with a first non-zero fraction, T.sub.1, of optical radiation that is sufficient for wavelength locking and/or power monitoring outside the laser cavity. A PIC including the semiconductor tunable ring laser, and to an opto-electronic system comprising such a PIC.

A wavelength variable optical resonator includes a wavelength variable filter and first and second waveguides each including a part inclined relative to a first end surface. A first optical amplifier includes a third waveguide including an active region on which reflection means is provided, the third waveguide being provided between a second end surface and a third end surface opposed to the second end surface and, the third waveguide further including a part inclined relative to the second end surface and extended from the second end surface. A second optical amplifier amplifies a laser light propagating through a fourth waveguide after the laser light whose wavelength is adjusted by the wavelength variable filter is input to the fourth waveguide via a fourth end surface facing the first end surface, the fourth waveguide including a part inclined relative to the fourth end surface and extended from the fourth end surface.