Multi-wavelength external cavity laser devices are generally described. The device includes a gain medium, a reflector, a wavelength selective element, and a chirped grating reflector. The wavelength selective element filters light having a first wavelength, and the chirped grating reflector reflects the light having the first wavelength. The light travels back to the reflector. As a result, the chirped grating reflector and the reflector define an optical cavity for the light having the first wavelength.

A vertical cavity surface emitting laser (VCSEL) may include an active region (e.g., one or more quantum wells) and a chirped pattern reflector. The active region may be configured to be electrically pumped such that the active region generates light having a fundamental mode and a higher order mode. The chirped pattern reflector may include a first portion presenting to the active region as a first portion of an effective mirror having a concave shape and a second portion presenting to the active region as a second portion of the effective mirror having a convex shape.

A multi-channel tunable laser includes: a frequency selective optical multiplexer comprising: a plurality of channel terminals for receiving/transmitting light; a plurality of channel waveguide blocks, each channel waveguide block comprising at least one reflectively terminated channel waveguide; and an optical coupling element optically coupling the plurality of channel terminals with the plurality of channel waveguide blocks, each of the channel waveguides of the plurality of channel waveguide blocks having a different length; a plurality of channel paths, each channel path coupled to a respective channel terminal of the plurality of channel terminals and comprising a gain element, a phase element and a reflective element; and a plurality of optical tuners, each one configured to tune the channel waveguides of a respective channel waveguide block of the plurality of channel waveguide blocks.

An optical semiconductor device comprises: a first insulating film provided on a semiconductor layer; a heater provided on the first insulating film; a second insulating film provided on the heater; and an electrode provided on the heater. The electrode extends on the second insulating film; the electrode is in contact with the heater; the second insulating film includes a first region on which the electrode is located; and a thickness of the first region of the second insulating film is greater than that of the first insulating film.

An optical element includes a distributed Bragg reflector, wherein the distributed Bragg reflector includes a first-order diffraction grating of a first-order period disposed in a central region, and second-order diffraction gratings of a second-order period having a coupling coefficient smaller than a coupling coefficient of the first-order diffraction grating and disposed in both end regions between which the central region is located.

A vertical cavity surface emitting laser (VCSEL) may include an active region (e.g., one or more quantum wells) and a chirped pattern reflector. The active region may be configured to be electrically pumped such that the active region generates light having a fundamental mode and a higher order mode. The chirped pattern reflector may include a first portion presenting to the active region as a first portion of an effective mirror having a concave shape and a second portion presenting to the active region as a second portion of the effective mirror having a convex shape.

A tunable laser for tuning a lasing mode based on light beams travelling through at least one block of channel waveguides with at least two tunable combs, includes: a frequency selective optical multiplexer comprising a first terminal for receiving/transmitting light, at least one block of channel waveguides, each channel waveguide having a reflectively coated first tail and a second tail, and an optical coupling element optically coupling the first terminal with the second tails of the channel waveguides of the at least one block of channel waveguides, each of the channel waveguides having a different length; a gain element generating a broad spectrum of light, the gain element coupling the first terminal of the frequency selective optical multiplexer with a reflective element.

Waveguide Bragg gratings, optical reflectors and lasers including optical reflectors are disclosed. The optical reflectors include a waveguide, perturbations proximate to the waveguide to create a Bragg grating in the waveguide, and a DC index control structure positioned to vary the DC index along at least a portion of the Bragg grating. In laser embodiments, the waveguide may be coupled to the second end of a semiconductor gain element to form an external cavity having an optical length and a cavity phase. The gain element and optical reflector may be monolithically integrated on a substrate or separate structures.

An optical transmitter that includes a wavelength tunable laser diode (LD) with a narrowed emission linewidth is disclosed. The optical transmitter further includes a feedback unit and an optical attenuator. The feedback unit, receiving a portion of laser light of the wavelength tunable LD, generates feedback light by rotating the polarization of the laser light by 905, and returns thus generated feedback light in the wavelength tunable LD. The optical attenuator adjusts power of the feedback light to reduce a line wide of the laser light, or frequency noises thereof.

An optical transmitter that includes a wavelength tunable laser diode (LD) with a narrowed emission linewidth is disclosed. The optical transmitter further includes a feedback unit and an optical attenuator. The feedback unit, receiving a portion of laser light of the wavelength tunable LD, generates feedback light by rotating the polarization of the laser light by 905, and returns thus generated feedback light in the wavelength tunable LD. The optical attenuator adjusts power of the feedback light to reduce a line wide of the laser light, or frequency noises thereof.