An example embodiment may include an interferometer. The interferometer may include a multimode waveguide with an input waveguide optically coupled to a first side of the multimode waveguide, for feeding a light signal to the multimode waveguide. The interferometer may also include a first waveguide at one end optically coupled to a second side of the multimode waveguide, and at the other end terminated by a first waveguide mirror. The interferometer may also include a second waveguide at one end optically coupled to the second side of the multimode waveguide and at the other end terminated by a second waveguide mirror. The multimode waveguide may be adapted to distribute the light signal towards the first and second waveguide mirror via the first waveguide and via the second waveguide.

A method includes etching a silicon layer to form a silicon slab and an upper silicon region over the silicon slab, and implanting the silicon slab and the upper silicon region to form a p-type region, an n-type region, and an intrinsic region between the p-type region and the n-type region. The method further includes etching the p-type region, the n-type region, and the intrinsic region to form a trench. The remaining portions of the upper silicon region form a Multi-Mode Interferometer (MMI) region. An epitaxy process is performed to grow a germanium region in the trench. Electrical connections are made to connect to the p-type region and the n-type region.

A method includes etching a silicon layer to form a silicon slab and an upper silicon region over the silicon slab, and implanting the silicon slab and the upper silicon region to form a p-type region, an n-type region, and an intrinsic region between the p-type region and the n-type region. The method further includes etching the p-type region, the n-type region, and the intrinsic region to form a trench. The remaining portions of the upper silicon region form a Multi-Mode Interferometer (MMI) region. An epitaxy process is performed to grow a germanium region in the trench. Electrical connections are made to connect to the p-type region and the n-type region.

An optical interferometer device is provided including a waveguide interferometer. The waveguide interferometer includes first and second waveguide arms in a waveguide plane, each waveguide arm including a n-type region and a p-type region forming a junction. The n-type region and the p-type region of the second waveguide arm are translationally symmetric with respect to the n-type region and the p-type region, respectively, of the first waveguide arm in the waveguide plane.

A polarization reducing apparatus includes a separating unit configured to separate input light into components having polarization directions orthogonal to each other; a winding waveguide of silicon formed on a silicon substrate in a winding manner, the winding waveguide transmitting a first component among the components separated by the separating unit; an optical path configured to have a shorter optical path length than the winding waveguide, the optical path transmitting a second component among the components separated by the separating unit; a combining unit configured to combine the first component and the second component; and an output unit configured to output light consisting of the first component and the second component combined by the combining unit.

An optical module includes a light-forming part and a protective member. The light-forming part includes a base member, a semiconductor light-emitting device, a lens, and a light-receiving device mounted on the base member and disposed, in the emission direction of the semiconductor light-emitting device, between the semiconductor light-emitting device and the lens. The light-receiving surface of the light-receiving device inclines toward the emission portion of the semiconductor light-emitting device such that an inclination angle is more than 0 and 90 or less, the inclination angle being an angle formed between the optical axis of the semiconductor light-emitting device and a plane including the light-receiving surface of the light-receiving device.

An optoelectronic circuit used with signal light comprises photonic devices disposed on a platform. The photonic devices are configured to condition the signal light and are fabricated with an optical characteristic being electronically tunable. A fabricated performance of the optical characteristic can be varied from a target performance due to a difference (e.g., alteration, change, error, or discrepancy) in the process used to fabricate the device. A ground bus, a power bus, and banks of electronic components are disposed on the platform in electrical communication with the photonic devices. The electronic components in a given bank are selectively configurable to tune the optical characteristic of the associated device so a variance can be diminished between the fabrication and target performances of the device's optical characteristic due to the difference in the fabrication process.

An interferometer for a photonic integrated circuit, the interferometer comprising: a first waveguide, a second waveguide, and a layer on at least one of the first waveguide or the second waveguide. The first waveguide having a first effective refractive index and a first path length along an optical propagation axis of the first waveguide. The second waveguide having a second effective refractive index and a second path length along an optical propagation axis of the second waveguide. The interferometer is configured to reduce change in a difference between: the first path length multiplied by the first effective refractive index; and the second path length multiplied by the second effective refractive index. The change in the difference is caused by at least one of an expansion force or a contraction force from the layer.

An optical delay between a first fiber and a second fiber is temperature compensated by combining fibers with different thermal path length changes. In some examples, fibers with different buffer coatings exhibit different path length changes per unit length and temperature. Combining such fibers in a fiber array provides a path length difference that is substantially independent of temperature.

An optoelectronic circuit used with signal light comprises photonic. The photonic devices are configured to condition the signal light and are fabricated with an optical characteristic being electronically tunable. A fabricated performance of the optical characteristic can be varied from a target performance due to a difference (e.g., alteration, change, error, or discrepancy) in the process used to fabricate the device. A ground bus, a power bus, and banks of electronic components are disposed on the platform in electrical communication with the photonic devices. The electronic components in a given bank are selectively configurable to tune the optical characteristic of the associated device so a variance can be diminished between the fabrication and target performances of the device's optical characteristic due to the difference in the fabrication process.