A spot-size converter includes first and second waveguide structures. The first waveguide structure extends longitudinally along a waveguide axis from a first end to a second end and is configured to support a first optical mode at the first end. The second waveguide structure is formed within the first waveguide structure. The second waveguide structure extends longitudinally between the first end and the second end. The second waveguide structure is configured to support a second optical mode at the second end. The second optical mode has a different diameter than the first optical mode. The second waveguide structure includes a waveguide core that has a first cross-sectional area in a first plane normal to the waveguide axis at the first end and a second cross-sectional area in a second plane normal to the waveguide axis at the second end. The second cross-sectional area is larger than the first cross-sectional area.

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.

This application provides a two-segment DBR laser and a monolithically integrated array light source chip, and relates to the field of optical communications. The two-segment DBR laser includes a grating region, a gain region, and a broadband reflector. The grating region and the broadband reflector are respectively disposed at two ends of the gain region. The grating region includes a first bottom liner, a first support structure, a first ridge waveguide structure, and a first heater. The first ridge waveguide structure is fastened by the first support structure and suspended in midair above the first bottom liner, and the first bottom liner, the first support structure, and the first ridge waveguide structure jointly form a cavity. The first heater is located on a surface that is of the first ridge waveguide structure and that faces away from the cavity.

Provided is a tunable semiconductor laser including an active gain region in which an optical signal is generated according to a modulation signal, a mode control region in which a resonant mode is controlled according to a mode control signal, and a signal chirp of the optical signal is compensated according to a first compensation signal determined based on the modulation signal, and a distributed Bragg reflector (DBR) region in which an oscillation wavelength of the optical signal is determined based on a wavelength selection signal for the optical signal, a second compensation signal for compensating for a thermal chirp of the optical signal on a basis of the modulation signal, and a heater signal provided to a heater electrode.

A system and method for providing laser diodes with broad spectrum is described. GaN-based laser diodes with broad or multi-peaked spectral output operating are obtained in various configurations by having a single laser diode device generating multiple-peak spectral outputs, operate in superluminescene mode, or by use of an RF source and/or a feedback signal. In some other embodiments, multi-peak outputs are achieved by having multiple laser devices output different lasers at different wavelengths.

It is provided a method for fabricating an electroabsorption modulated laser comprising generating a single mode laser section and an electroabsorption modulator section, comprising fabricating at least one n-doped layer of the laser section and at least one n-doped layer of the modulator section; generating an isolating section for electrically isolating at least the n-doped layer of the laser section and the n-doped layer of the modulator section from one another. Generating the isolating section comprises epitaxially growing at least one isolating layer and structuring the isolating layer before the generation of the n-doped layer of the laser section and the n-doped layer of the modulator section.

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 tunable semiconductor laser including an active gain region in which an optical signal is generated according to a modulation signal, a mode control region in which a resonant mode is controlled according to a mode control signal, and a signal chirp of the optical signal is compensated according to a first compensation signal determined based on the modulation signal, and a distributed Bragg reflector (DBR) region in which an oscillation wavelength of the optical signal is determined based on a wavelength selection signal for the optical signal, a second compensation signal for compensating for a thermal chirp of the optical signal on a basis of the modulation signal, and a heater signal provided to a heater electrode.

A directly modulated semiconductor laser whose optical output can be modulated by varying the transmittance of an end reflector of the laser cavity. In an example embodiment, the end reflector can be implemented using a lightwave circuit in which optical waveguides are arranged to form an optical interferometer. At least one of the optical waveguides may include a waveguide section configured to modulate the phase of an optical beam passing therethrough in response to an electrical radio-frequency drive signal in a manner that causes the transmittance and reflectance of the end reflector to be modulated accordingly. Advantageously, relatively high (e.g., >10 GHz) phase and/or amplitude modulation speeds of the optical output can be achieved in this manner to circumvent the inherent modulation-speed limitations of the laser's gain medium.

There is provided a semiconductor optical integrated device having a DFB laser, an EA modulator, and an SOA monolithically integrated, and an output light intensity of the semiconductor optical integrated device is maintained constant. The semiconductor optical integrated device includes: a DFB laser; an EA modulator connected to the DFB laser; an SOA monolithically integrated with the DFB laser and the EA modulator on a same substrate and connected to an output end of the EA modulator; and an optical receiver disposed on an output end side of the SOA and having a same composition as the SOA. The optical receiver is configured to monitor change in a detection value according to an intensity of input light to the optical receiver such that drive currents flowing in the DFB laser and the SOA are feedback controlled.