A method or apparatus for narrowing the linewidth of a single mode laser is provided. The linewidth of a single mode laser is narrowed by injecting an optical feedback simultaneously into the first laser cavity mirror and the second laser cavity mirror of the single mode laser.

A thermally tunable laser includes: a substrate; a laser resonator, wherein the laser resonator includes a gain section, and wherein the laser resonator includes a tuning section; a heating arrangement; a heat sink arrangement for dissipating a heat flow from the laser resonator to the heat sink arrangement; and a hole arrangement for influencing the heat flow from the laser resonator to the heat sink arrangement, wherein the hole arrangement is arranged between the substrate and the heat sink arrangement, wherein one or more holes of the hole arrangement include at least one hole being arranged within a horizontal range of the tuning section, so that a thermal resistance between the tuning section and the heat sink arrangement is increased.

A method for controlling an electromagnetic radiation source to produce single mode operation having an optimized side-mode suppression ratio over a set of wavelengths within a prescribed temporal profile. The electromagnetic radiation source is configured to output electromagnetic radiation at a given wavelength based upon parameters. The method includes determining a set of parameter combinations that satisfy a condition for a desired set of wavelengths and a minimum side mode suppression ratio over the range of wavelengths. The set of parameter combinations define sub-paths for nearly arbitrary transitions from one wavelength to another wavelength. Combinations of select sub-paths provide a multivariate path for transitioning over the range of wavelengths. The method also includes controlling the semiconductor laser to emit electromagnetic radiation over the range of wavelengths by traversing the multivariate path in a desired manner.

According to an embodiment, a wavelength tunable laser comprising a gain region and a wavelength tunable area is disclosed. The wavelength tunable area comprises: a lower clad layer; a passive optical waveguide positioned on the lower clad layer; an upper clad layer positioned on the passive optical waveguide; a drive electrode positioned on the upper clad layer; a current blocking layer positioned on the drive electrode; a heater positioned on the current blocking layer; and a first insulating groove and a second insulating groove which are positioned so as to face each other with the passive optical waveguide therebetween.

A waveguide based wavelength-tunable laser formed on a semiconductor substrate includes a first reflector from which laser light is output, a second reflector configuring a laser resonator together with the first reflector, a gain portion that is provided between the first reflector and the second reflector, at least two wavelength filters that can adjust wavelength characteristics and adjust a wavelength of the laser light, and a phase adjuster that adjusts an optical path length in the laser resonator, and a waveguide is formed to fold back an optical path by an angle of substantially 180 degrees between the first reflector and the second reflector.

A laser comprising a laser cavity formed by a first optical reflector, a gain region, a second optical reflector having a plurality of reflection peaks, and at least one optically active region. The first mirror may be a DBR or comb mirror and the second mirror may be a comb mirror. The spectral reflectance of the second optical reflector is adjusted at least partially based on an electric signal received form the optically active region such that only one reflection peak is aligned with a cavity mode formed by the first and second reflector.

The optical module includes: a housing having first and second end walls and a pair of side walls; a semiconductor laser element; a first TEC; a wavelength locker unit including an optical splitting component and an etalon filter; and a second TEC. The second end wall is provided with a feedthrough. The pair of side walls is not provided with an external connection terminal. The second TEC is disposed between the first TEC and the second end wall and has: a first substrate thermally coupled to a bottom surface of the housing; a second substrate thermally coupled to the etalon filter; and a heat transfer part that transfers heat. The optical module further includes a wiring pattern that is arranged side by side with the heat transfer part and that supplies electric power to the first TEC from the feedthrough.

A process of forming a semiconductor optical device is disclosed. The semiconductor optical device provides a waveguide structure accompanied with a heater for varying a temperature of the waveguide structure. The process includes steps of: (a) forming a striped mask on a semiconductor substrate; (b) selectively growing a dummy layer on the semiconductor substrate; (c) removing the patterned mask; (d) burying the dummy layer by a supplemental layer; (e) exposing a portion of the dummy layer by etching a portion of the supplemental layer; (f) and removing the dummy layer by immersing the dummy layer within a solution that shows an etching rate for the dummy layer enough faster than an etching rate for the supplemental layer and the substrate so as to leave a void in a region the dummy layer had existed.

A tunable laser is provided, including a first reflector, a second reflector, a phase adjustment area, a gain area, a first detector, a second detector, and a controller. The phase adjustment area is located between the first reflector and the gain area, the gain area is located between the phase adjustment area and the second reflector, a reflectivity of the first reflector is adjustable, and a reflectivity of the second reflector is adjustable. The first detector is configured to convert an optical signal of the first reflector into a first electrical signal. The second detector is configured to convert an optical signal of the second reflector into a second electrical signal. The controller is configured to adjust at least one of the reflectivity of the first reflector or the reflectivity of the second reflector based on the first electrical signal and the second electrical signal.

A wavelength-tunable light source includes a wavelength-tunable laser including a first region and a second region each of which includes at least one of heaters, a frequency locker configured to receive output light of the wavelength-tunable laser and output two electric control signals whose phases are mutually different by 90 and having frequency period with respect to frequency of the output light, a thermal electric cooler on which the wavelength-tunable laser and the frequency locker are mounted, and a controller configured to control temperature of the heaters, and the thermal electric cooler on the basis of any one of the two electric control signals.