Abstract: A photonic integrated circuit (PIC) is described. This PIC includes a semiconductor-barrier layer-semiconductor diode in an optical waveguide that conveys an optical signal, where the barrier layer is an oxide or a high-k material. Moreover, semiconductor layers in the semiconductor-barrier layer-semiconductor diode may include geometric features (such as a periodic pattern of holes or trenches) that create a lattice-shifted photonic crystal optical waveguide having a group velocity of light that is lower than the group velocity of light in the first semiconductor layer and the second semiconductor layer without the geometric features. The optical waveguide is included in an optical modulator, such as a Mach-Zehnder interferometer (MZI).

Abstract: A multi-chip module (MCM) is described. This MCM includes two substrates that are passively self-assembled on another substrate using hydrophilic and hydrophobic materials on facing surfaces of the substrates and liquid surface tension as the restoring force. In particular, regions with a hydrophilic material on the two substrates overlap regions with the hydrophilic material on the other substrate. These regions on the other substrate may be surrounded by a region with a hydrophobic material. In addition, spacers on a surface of at least one of the two substrates may align optical waveguides disposed on the two substrates, so that the optical waveguides are coplanar. This fabrication technique may allow low-loss hybrid optical sources to be fabricated by edge coupling the two substrates. For example, a first of the two substrates may be a III/V compound semiconductor and a second of the two substrates may be a silicon-on-insulator photonic chip.

Abstract: A photonic integrated circuit (PIC) is described. This PIC includes a grating coupler for surface-normal coupling that has an alternating pattern of grating teeth and grating trenches, where the grating trenches are filled with an electro-optical material. By applying an electric potential to the grating teeth, the index of refraction of the electro-optical material can be modified.

Abstract: A fabrication technique for cleaving a substrate in an integrated circuit is described. During this fabrication technique, a trench is defined on a back side of a substrate. For example, the trench may be defined using photoresist and/or a mask pattern on the back side of the substrate. The trench may extend from the back side to a depth less than a thickness of the substrate. Moreover, a buried-oxide layer and a semiconductor layer may be disposed on a front side of the substrate. In particular, the substrate may be included in a silicon-on-insulator technology. By applying a force proximate to the trench, the substrate may be cleaved to define a surface, such as an optical facet. This surface may have high optical quality and may extend across the substrate, the buried-oxide layer and the semiconductor layer.

Abstract: A fabrication technique for cleaving a substrate in an integrated circuit is described. During this fabrication technique, a trench is defined on a back side of a substrate. For example, the trench may be defined using photoresist and/or a mask pattern on the back side of the substrate. The trench may extend from the back side to a depth less than a thickness of the substrate. Moreover, a buried-oxide layer and a semiconductor layer may be disposed on a front side of the substrate. In particular, the substrate may be included in a silicon-on-insulator technology. By applying a force proximate to the trench, the substrate may be cleaved to define a surface, such as an optical facet. This surface may have high optical quality and may extend across the substrate, the buried-oxide layer and the semiconductor layer.

Abstract: A multi-chip module (MCM) is described. This MCM includes two substrates that are passively self-assembled on another substrate using hydrophilic and hydrophobic materials on facing surfaces of the substrates and liquid surface tension as the restoring force. In particular, regions with a hydrophilic material on the two substrates overlap regions with the hydrophilic material on the other substrate. These regions on the other substrate may be surrounded by a region with a hydrophobic material. In addition, spacers on a surface of at least one of the two substrates may align optical waveguides disposed on the two substrates, so that the optical waveguides are coplanar. This fabrication technique may allow low-loss hybrid optical sources to be fabricated by edge coupling the two substrates. For example, a first of the two substrates may be a III/V compound semiconductor and a second of the two substrates may be a silicon-on-insulator photonic chip.

Abstract: An optical device is described. This optical device includes optical components having resonance wavelengths that match target values with a predefined accuracy (such as 0.1 nm) and with a predefined time stability (such as permanent or an infinite time stability) without thermal tuning and/or electronic tuning. The stable, accurate resonance wavelengths may be achieved using a wafer-scale, single (sub-second) shot trimming technique that permanently corrects the phase errors induced by material variations and fabrication inaccuracies in the optical components (and, more generally, resonant silicon-photonic optical components). In particular, the trimming technique may use photolithographic exposure of the optical components on the wafer in parallel, with time-modulation for each individual optical component based on active-element control.

Abstract: An integrated circuit includes an optical source (such as a laser) with a lens, which is disposed on an isolator. This isolator is disposed on a semiconductor layer in a silicon-on-insulator (SOI) platform that includes an optical coupler and an optical waveguide. During operation, the optical source generates an optical signal that propagates toward the isolator so that the lens focuses the optical signal. Furthermore, the isolator reduces or eliminates back reflection of the optical signal toward the optical source, and the optical coupler couples the optical signal into the optical waveguide.

Abstract: When an unsafe port with a loss of signal is detected, a transceiver may enable one laser in a group of lasers associated with the unsafe port and may disable the remaining lasers. Then, the transceiver may instruct a transmitter associated with the one laser to transmit an optical signal on the unsafe port using a reduced transmit power that is less than a threshold value associated with the Class 1 conditions and at a different time than enabled lasers in other groups of lasers. Alternatively, for a safe port on which valid communication is received, the transceiver may enable lasers in a group of lasers associated with the safe port. Then, the transceiver may instruct transmitters associated with the lasers in this group of lasers to transmit optical signals on the safe port using a normal transmit power for the lasers that is greater than the threshold value.

Abstract: An optical device includes an optical reflector based on a coupled-loopback optical waveguide. In particular, an input port, an output port and an optical loop in arms of the optical reflector are optically coupled to a directional coupler. The directional coupler evanescently couples an optical signal between the arms. For example, the directional coupler may include: a multimode interference coupler and/or a Mach-Zehnder Interferometer (MZI). Moreover, destructive interference during the evanescent coupling determines the reflection and transmission power coefficients of the optical reflector.

Abstract: An integrated circuit is described. This integrated circuit includes a ferroelectric layer disposed on top of the ring resonator, which has a resonance wavelength. The ferroelectric layer is positioned between electrical contacts. Moreover, there may be amorphous semiconductor materials between the electrical contacts and the ferroelectric layer. For example, the amorphous semiconductor materials may include: p-type amorphous silicon and/or n-type amorphous silicon. By applying a reverse-bias voltage across the electrical contacts, an electric field is generated in a plane approximately parallel to a top surface of the ring resonator. This electric field electro-optically tunes the resonance wavelength. The ring resonator may operate at low voltage and can be integrated with a silicon optical waveguide on a silicon-on-insulator (SOI) platform.

Abstract: An optical device includes an optical reflector based on a coupled-loopback optical waveguide. In particular, an input port, an output port and an optical loop in arms of the optical reflector are optically coupled to a directional coupler. The directional coupler evanescently couples an optical signal between the arms. For example, the directional coupler may include: a multimode interference coupler and/or a Mach-Zehnder Interferometer (MZI). Moreover, destructive interference during the evanescent coupling determines the reflection and transmission power coefficients of the optical reflector.

Abstract: An optical device is described. This optical device includes optical components having resonance wavelengths that match target values with a predefined accuracy (such as 0.1 nm) and with a predefined time stability (such as permanent or an infinite time stability) without thermal tuning and/or electronic tuning. The stable, accurate resonance wavelengths may be achieved using a wafer-scale, single (sub-second) shot trimming technique that permanently corrects the phase errors induced by material variations and fabrication inaccuracies in the optical components (and, more generally, resonant silicon-photonic optical components). In particular, the trimming technique may use photolithographic exposure of the optical components on the wafer in parallel, with time-modulation for each individual optical component based on active-element control.

Abstract: An integrated optical device includes an electro-absorption modulator disposed on a top surface of an optical waveguide. The electro-absorption modulator includes germanium disposed in a cavity between an n-type doped silicon sidewall and a p-type doped silicon sidewall. By applying a voltage between the n-type doped silicon sidewall and the p-type doped silicon sidewall, an electric field can be generated in a plane of the optical waveguide, but perpendicular to a propagation direction of the optical signal. This electric field shifts a band gap of the germanium, thereby modulating the optical signal.

Abstract: A chip package includes an optical integrated circuit (such as a hybrid integrated circuit) and an integrated circuit that are proximate to each other in the chip package. The integrated circuit includes electrical circuits that modulate data, communicate data, and serialize/deserialize data, and the optical integrated circuit communicates optical signals with very high bandwidth. Moreover, a front surface of the integrated circuit is electrically coupled to a top surface of an interposer, and a top surface of the integrated circuit is electrically coupled to a front surface of the optical integrated circuit. Furthermore, a bottom surface of the optical integrated circuit faces the top surface of the interposer, and the front surface of the optical integrated circuit is optically coupled to an optical-fiber receptacle, which in turn is optically coupled to an optical-fiber connector.

Abstract: An optical source is described. This optical source includes a semiconductor optical amplifier, with a semiconductor other than silicon, which provides a gain medium. In addition, a photonic chip, optically coupled to the semiconductor optical amplifier, includes: an optical waveguide that conveys the optical signal; and a pair of ring-resonator modulators that modulate the optical signal. Furthermore, the pair of ring-resonator modulators is included within an optical cavity in the optical source. For example, the optical cavity may be defined by a reflective coating on one edge of the semiconductor optical amplifier and a reflector on one end of the optical waveguide. Alternatively, the optical cavity may be defined by reflectors on ends of the optical waveguide.

Abstract: A hybrid optical source includes a substrate with an optical amplifier (such as a III-V semiconductor optical amplifier). The substrate is coupled at an angle (such as an angle between 0 and 90°) to a silicon-on-insulator chip. In particular, the substrate may be optically coupled to the silicon-on-insulator chip by an optical coupler (such as a diffraction grating or a mirror) that efficiently couples (i.e., with low optical loss) an optical signal into a sub-micron silicon-on-insulator optical waveguide. Moreover, the silicon-on-insulator optical waveguide optically couples the light to a reflector to complete the hybrid optical source.

Abstract: A hybrid optical source that provides an optical signal having a wavelength (or a narrow band of wavelengths) is described. This hybrid optical source includes an optical amplifier (such as a III-V semiconductor optical amplifier) that is butt-coupled or vertically coupled to a silicon-on-insulator (SOI) platform, and which outputs an optical signal. The SOI platform includes an optical waveguide that conveys the optical signal. A temperature-compensation element included in the optical waveguide compensates for temperature dependence of the indexes of refraction of the optical amplifier and the optical waveguide. In addition, a reflector, adjacent to the optical waveguide after the temperature-compensation element, reflects a portion of the optical signal and transmits another portion of the optical signal that has the wavelength.

Abstract: A technique for fabricating a hybrid optical source is described. During this fabrication technique, a III-V compound-semiconductor active gain medium is integrated with a silicon-on-insulator (SOI) chip (or wafer) using edge coupling to form a co-planar hybrid optical source. Using a backside etch-assisted cleaving technique, and a temporary transparent substrate with alignment markers, a III-V compound-semiconductor chip with proper edge polish and coating can be integrated with a processed SOI chip (or wafer) with accurate alignment. This fabrication technique may significantly reduce the alignment complexity when fabricating the hybrid optical source, and may enable wafer-scale integration.

Abstract: An optical-source monitor images and diffracts received optical signals using an optical device that has a reflective geometry. For example, the optical device may include a diffraction grating on a curved surface, such as an echelle grating. By imaging and diffracting the optical signals, the optical device may couple to the optical signals on different diffraction orders of the optical device (which have different carrier wavelengths) from input optical waveguides to corresponding output optical waveguides. Then, output power monitors may measure the output power levels of the optical signals, and control logic may provide wavelength control signals to optical sources that provide the optical signals based on measured output power levels.