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.

An optical functional device includes: first and second optical couplers each including a multi-mode interferometer waveguide portion having a first end portion and a second end portion, two units of first input/output ports and two units of second input/output ports; and first and second arc-shaped waveguides each optically connecting one of the first and second input/output ports of the first and second optical coupler and one of the first and second input/output ports of the second optical coupler, respectively. Further, the first optical coupler, the second optical coupler, the first arc-shaped waveguide, and the second arc-shaped waveguide constitute a ring resonator, and each of the multi-mode waveguide portions of the first optical coupler and the second optical coupler have a narrow portion, an average width of the narrow portion in a longitudinal direction being narrower than widths at the first end portion and the second end portion.

A two-kappa DBR laser includes an active section, a HR mirror, a first DBR section, and a second DBR section. The HR mirror is coupled to a rear of the active section. The first DBR section is coupled to a front of the active section, the first DBR section having a first DBR grating with a first kappa κ1. The second DBR section is coupled to a front of the first DBR section such that the first DBR section is positioned between the active section and the second DBR section. The second DBR section has a second DBR grating with a second kappa κ2 less than the first kappa κ1. The two-kappa DBR laser is configured to operate in a lasing mode and has a DBR reflection profile that includes a DBR reflection peak. The lasing mode is aligned to a long wavelength edge of the DBR reflection peak.

An on-chip wavelength locker may include an optical waveguide splitter to split an input optical signal received from a laser. The on-chip wavelength locker may include a plurality of integrated periodic optical elements, each to receive a respective portion of the input optical signal after splitting of the input optical signal by the optical waveguide splitter, and provide, based on the respective portion of the input optical signal, a respective periodic output optical signal of a plurality of periodic output optical signals. Each periodic output optical signal, of the plurality of periodic output optical signals, may be phase shifted with respect to other periodic output optical signals of the plurality of periodic output optical signals. The on-chip wavelength locker may include a plurality of integrated photodiodes to receive the plurality of periodic output optical signals in association with wavelength locking the laser.

A semiconductor optical device includes a substrate including a waveguide made of silicon and a semiconductor layer joined to the substrate so as to overlap the waveguide and including a diffraction grating formed of a first semiconductor layer and a second semiconductor layer having different refractive indices. The waveguide includes a bent portion and a plurality of straight portions that are connected to each other by the bent portion and that extend straight. The first semiconductor layer and the second semiconductor layer are each made of a compound semiconductor. The second semiconductor layer is embedded in the first semiconductor layer and includes a plurality of portions arranged in a direction in which the plurality of straight portions extend. The diffraction grating is positioned above the plurality of straight portions.

A wavelength tunable laser device includes a substrate including silicon, the substrate having a waveguide, a first semiconductor element bonded to the substrate, the first semiconductor element including an active layer of a group III-V compound semiconductor, and a second semiconductor element bonded to the substrate, the second semiconductor element facing to the first semiconductor element in a direction along which light emitted from the first semiconductor element propagates, the second semiconductor element including a grating formed of a group III-V compound semiconductor. The grating selects a wavelength of light.

Disclosed is a Vernier effect DBR laser that has uniform laser injection current pumping along the length of the laser. The laser can include one or more tuning elements, separate from the laser injection element, and these tuning elements can be used to control the temperature or modal refractive index of one or more sections of the laser. The refractive indices of each diffraction grating can be directly controlled by temperature changes, electro optic effects, or other means through the one or more tuning elements. With direct control of the temperature and/or refractive indices of the diffraction gratings, the uniformly pumped Vernier effect DBR laser can be capable of a wider tuning range. Additionally, uniform pumping of the laser through a single electrode can reduce or eliminate interfacial reflections caused by, for example, gaps between metal contacts atop the laser ridge, which can minimize multi-mode operation and mode hopping.

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 method for tuning an emission wavelength of a laser device, including: acquiring a drive condition of a wavelength tunable laser diode to make the wavelength tunable laser diode oscillate at a wavelength from a memory; driving a first thermo-cooler and a first heater based on the drive condition of the wavelength tunable laser diode; determining whether respective control values of the first thermo-cooler and the first heater are reached within a first range of target values; and driving a gain region after the control values have been reached within the first range.

Disclosed are a wavelength-selectable laser diode and an optical communication apparatus including the same. The wavelength-selectable laser diode includes a substrate, which includes a gain region, a tuning region spaced apart from the gain region, and a phase adjusting region between the tuning region and the gain region, a waveguide layer on the substrate, a clad layer on the waveguide layer, and gratings disposed on the substrate or the clad layer in the gain region and the tuning region.