Abstract: A mode-locked semiconductor laser capable of changing the spacing between the carrier frequencies of its output comb. In an example embodiment, the mode-locked semiconductor laser is implemented as a hybrid solid-state device comprising a III-V semiconductor chip and a silicon chip attached to one another to form a laser cavity. The III-V semiconductor chip includes a gain medium configured to generate light in response to being electrically and/or optically pumped. The silicon chip includes a plurality of optical waveguides arranged to provide multiple optical paths of different effective lengths for the light generated in the laser cavity. Different optical paths can be controllably selected, using one or more optical switches connected between the optical waveguides, to change the effective optical length of the laser cavity and, as a result, the output-comb frequency spacing. In some embodiments, the output-comb frequency spacing can be changeable at least by a factor of 1.5.

Abstract: An apparatus includes an optical amplifier waveguide and an optical reflector located to reflect back some light received at or near a first end of the optical amplifier waveguide. The apparatus also includes another optical waveguide having a first end located to receive light at or near a second end of the optical amplifier waveguide, and the another optical waveguide having a sequence of optical ring resonators optically connected there along with each of the optical ring resonators being configured to have a different free spectral range. A system and a method are also included.

Abstract: A mode-locked semiconductor laser capable of changing the spacing between the carrier frequencies of its output comb. In an example embodiment, the mode-locked semiconductor laser is implemented as a hybrid solid-state device comprising a III-V semiconductor chip and a silicon chip attached to one another to form a laser cavity. The III-V semiconductor chip includes a gain medium configured to generate light in response to being electrically and/or optically pumped. The silicon chip includes a plurality of optical waveguides arranged to provide multiple optical paths of different effective lengths for the light generated in the laser cavity. Different optical paths can be controllably selected, using one or more optical switches connected between the optical waveguides, to change the effective optical length of the laser cavity and, as a result, the output-comb frequency spacing. In some embodiments, the output-comb frequency spacing can be changeable at least by a factor of 1.5.

Abstract: An apparatus includes an optical amplifier waveguide and an optical reflector located to reflect back some light received at or near a first end of the optical amplifier waveguide. The apparatus also includes another optical waveguide having a first end located to receive light at or near a second end of the optical amplifier waveguide, and the another optical waveguide having a sequence of optical ring resonators optically connected there along with each of the optical ring resonators being configured to have a different free spectral range. A system and a method are also included.

Abstract: A hybrid laser structure (comprising III-V gain material and a silicon-based photonic integrated circuit) is configured to control the number of generated mode-locked wavelengths by including an optical wavelength filter within the photonic integrated circuit portion of the laser cavity. The optical wavelength filter is used to control the number of comb lines that are supported by the laser cavity, filtering out a set of non-selected mode-locked wavelengths to control the generated number. The optical filter may be passive or active, and the number of generated comb lines may be fixed or adjustable, as desired.