Abstract: An optical modulator is described. This optical modulator may be implemented using silicon-on-insulator (SOI) technology. In particular, a semiconductor layer in an SOI platform may include a photonic crystal having a group velocity of light that is less than that of the semiconductor layer. Moreover, an optical modulator (such as a Mach-Zehnder interferometer) may be implemented in the photonic crystal with a vertical junction in the semiconductor layer. During operation of the optical modulator, an input optical signal may be split into two different optical signals that feed two optical waveguides, and then subsequently combined into an output optical signal. Furthermore, during operation, time-varying bias voltages may be applied across the vertical junction in the optical modulator using contacts defined along a lateral direction of the optical modulator.

Abstract: The disclosed embodiments relate to a system that locks a wavelength of a hybrid laser to a wavelength of a reference laser, wherein a lasing cavity of the hybrid laser includes a reflective gain medium (RGM) comprising an optical gain material coupled with an associated reflector, a phase tuner, a laser ring filter and a silicon mirror. During operation, while the hybrid laser is turned off, the system tunes a reference ring filter to the wavelength of the reference laser. Next, the system turns on the hybrid laser. The system then tunes the laser ring filter in the hybrid laser to the reference ring filter. Finally, the system adjusts the phase tuner in the hybrid laser to align a lasing cavity mode of the hybrid laser with the tuned laser ring filter.

Abstract: The disclosed embodiments relate to a system that implements a hybrid laser. This system includes a reflective gain medium (RGM) comprising an optical gain material coupled to a mirror. This RGM is coupled to a spot-size converter (SSC), which optically couples the RGM to an optical reflector through a silicon waveguide. The SSC converts an optical mode-field size of the RGM to an optical mode-field size of the silicon waveguide. During operation, the RGM, the spot-size converter, the silicon waveguide and the silicon mirror collectively form a lasing cavity, wherein an effective thermo-optic coefficient (TOC) of a portion of the lasing cavity that passes through the optical gain material and the SSC material is substantially the same as the TOC of silicon. Finally, a laser output is optically coupled out of the lasing cavity.

Abstract: A reflectivity test circuit is described. The reflectivity test circuit includes a symmetric structure that cancels errors in the reflectivity measurements. In particular, the reflectivity test circuit includes an optical waveguide that is optically coupled to two optical ports and two optical couplers. The optical couplers are optically coupled to adjacent optical waveguides, at least one of which is optically coupled to a third optical port and the mirror. Moreover, a length of the optical waveguide is chosen to match the round-trip optical path length in at least the one of the adjacent optical waveguides. During operation, control logic determines the reflectivity of the mirror based at least on a ratio of an optical power measured on one of the two optical ports to an input optical power on the third optical port.

Abstract: A transceiver separates wavelength-division-multiplexing (WDM) components into two groups, one of which is more sensitive to temperature than the other group. The temperature-sensitive group of optical components is implemented on a first substrate in the transceiver that has a lower thermo-optic coefficient than a second substrate in the transceiver, which contains the group of optical components that is less temperature sensitive. In particular, the first substrate, which may be glass, may include WDM components that convey optical signals having multiple carrier wavelengths. Moreover, the second substrate, such as a silicon substrate (e.g., a silicon-on-insulator platform), may include multiple parallel optical paths with optical components, in which a given optical path conveys an optical signal having a given carrier wavelength.

Abstract: An optical source is described. This optical source includes a semiconductor optical amplifier (with a semiconductor other than silicon) that provides an optical gain medium and that includes a reflector. Moreover the hybrid external cavity laser includes a photonic chip with: an optical waveguide that conveys an optical signal output by the semiconductor optical amplifier; and a ring resonator, having a resonance wavelength, which reflects at least a resonance wavelength in the optical signal, where the reflector and the ring resonator define an optical cavity. Furthermore, the photonic chip includes: a thermal-tuning mechanism that adjusts the resonance wavelength; a photo-detector that measures an optical power output by the ring resonator; and control logic that adjusts the temperature of the ring resonator based on the measured optical power to lock a cavity mode of the optical cavity to a carrier wavelength.

Abstract: An optical receiver is described. Using silicon-photonic components that support a single polarization, the output of an optical receiver is independent of the polarization of an optical signal. In particular, using a polarization-diversity technique, the two orthogonal polarizations in a single-mode optical fiber are split in two and processed independently. For example, the two optical signals may be provided by a polarization-splitting grating coupler. Subsequently, a redistribution element provides mixtures of the two optical signals. Next, a wavelength channel in the two mixed optical signals is selected using a wavelength-selective filter (for example, using ring-resonator drop filters or an echelle grating) and converted into an electrical signal at an optical detector (such as a photodetector) to achieve polarization-independent operation.

Abstract: A multi-chip module (MCM) is described. This MCM includes a driver integrated circuit that includes electrical circuits, a photonic chip, an interposer, and an optical gain chip. The photonic chip may be implemented using a silicon-on-insulator technology, and may include an optical waveguide that conveys an optical signal and traces that are electrically coupled to the driver integrated circuit. Moreover, the interposer may be electrically coupled to the traces. Furthermore, the optical gain chip may include a III/V compound semiconductor (and, more generally, a semiconductor other than silicon), and may include a second optical waveguide that conveys the optical signal and that is vertically aligned with the optical waveguide relative to a top surface of the interposer. Additionally, the optical gain chip may be electrically coupled to the interposer.

Abstract: An optical receiver includes: an active transimpedance amplifier (TIA) that converts a photocurrent from a photosensor into an active voltage signal; a high-speed amplifier that amplifies the active voltage signal to produce an amplified voltage signal that comprises an output for the optical receiver; and a reference-voltage-generation circuit that generates a reference voltage for the high-speed amplifier. This reference-voltage-generation circuit includes a dummy TIA that is identical to the active TIA, but does not receive a live input signal, and produces a dummy voltage signal. It also includes a low-speed amplifier which includes: an active input that receives the active voltage signal from the active TIA output; a dummy input that receives the dummy voltage signal from the dummy TIA output; and an output that controls directly or indirectly the reference voltage for the high-speed amplifier.

Abstract: An optical source is described. This optical source includes a semiconductor optical amplifier (with a semiconductor other than silicon) that provides an optical gain medium and that includes a reflector. Moreover the hybrid external cavity laser includes a photonic chip with: an optical waveguide that conveys an optical signal output by the semiconductor optical amplifier; and a ring resonator, having a resonance wavelength, which reflects at least a resonance wavelength in the optical signal, where the reflector and the ring resonator define an optical cavity. Furthermore, the photonic chip includes: a thermal-tuning mechanism that adjusts the resonance wavelength; a photo-detector that measures an optical power output by the ring resonator; and control logic that adjusts the temperature of the ring resonator based on the measured optical power to lock a cavity mode of the optical cavity to a carrier wavelength.

Abstract: An optical transmitter includes: a set of reflective semiconductor optical amplifiers (RSOAs) or other reflective gain media, a set of ring filters, a set of intermediate waveguides, a shared waveguide, a shared loop mirror, and an output waveguide. Each intermediate waveguide channels light from an RSOA in proximity to an associated ring filter to cause optically coupled light to circulate in the associated ring filter. The shared waveguide is coupled to the shared loop mirror, and is located in proximity to the set of ring filters, so that light circulating in each ring filter causes optically coupled light to flow in the shared waveguide. Each RSOA forms a lasing cavity with the shared loop reflector, wherein each lasing cavity has a different wavelength associated with a resonance of its associated ring filter. The output waveguide is optically coupled to the shared loop mirror and includes an electro-optical modulator.

Abstract: A hybrid optical source comprises an optical gain chip containing an optical gain material that provides an optical signal, and an optical reflector chip including an optical reflector. It also includes a semiconductor-on-insulator (SOI) chip, which comprises a semiconductor layer having a planarized surface facing the semiconductor reflector. The semiconductor layer includes: an optical coupler to redirect the optical signal to and from the planarized surface; and an optical waveguide to convey the optical signal from the optical coupler. While assembling these chips, a height of the optical gain material is referenced against the planarized surface of the semiconductor layer, a height of the optical reflector is referenced against the planarized surface of the semiconductor layer, and the optical reflector is aligned with the optical coupler, so that the optical signal emanating from the optical gain material is reflected by the optical reflector and into the optical coupler.

Abstract: A hybrid optical source comprises an optical gain chip containing an optical gain material that provides an optical signal, and an optical reflector chip including an optical reflector. It also includes a semiconductor-on-insulator (SOI) chip, which comprises a semiconductor layer having a planarized surface facing the semiconductor reflector. The semiconductor layer includes: an optical coupler to redirect the optical signal to and from the planarized surface; and an optical waveguide to convey the optical signal from the optical coupler. While assembling these chips, a height of the optical gain material is referenced against the planarized surface of the semiconductor layer, a height of the optical reflector is referenced against the planarized surface of the semiconductor layer, and the optical reflector is aligned with the optical coupler, so that the optical signal emanating from the optical gain material is reflected by the optical reflector and into the optical coupler.

Abstract: A dual-ring-modulated laser includes a gain medium having a reflective end coupled to an associated gain-medium reflector and an output end, which is coupled to a reflector circuit through an input waveguide to form a lasing cavity. The reflector circuit comprises: a first ring modulator; a second ring modulator; and a shared waveguide that optically couples the first and second ring modulators together. The first and second ring modulators have resonance peaks that are tuned to be offset in alignment from each other to provide an effective reflectance having a flat-top response, which is aligned with an associated lasing cavity mode. The first and second ring modulators are driven in tandem based on the same electrical input signal, whereby the resonance peaks of the first and second ring modulators shift wavelengths in the same direction during modulation, and an effective reflectance stays within the flat-top wavelength range.

Abstract: A tunable laser includes a reflective silicon optical amplifier (RSOA) with a reflective end and an interface end and an array of narrow-band reflectors, which each have a different center wavelength. It also includes a silicon-photonic optical switch, having an input port and N output ports that are coupled to a different narrow-band reflector in the array of narrow-band reflectors. The tunable laser also includes an optical waveguide coupled between the interface end of the RSOA and the input of the silicon-photonic optical switch. The frequency of this tunable laser can be tuned in discrete increments by selectively coupling the input port of the silicon-photonic optical switch to one of the N output ports, thereby causing the RSOA to form a lasing cavity with a selected narrow-band reflector coupled to the selected output port. The tunable laser also includes a laser output optically coupled to the lasing cavity.

Abstract: A tunable laser includes a semiconductor optical amplifier (SOA) having a reflective end coupled to a shared reflector and an output end, which is coupled to a demultiplexer through an input waveguide. The demultiplexer comprises a set of Mach-Zehnder (MZ) lattice filters, which function as symmetric de-interleaving wavelength splitters, that are cascaded to form a binary tree that connects an input port, which carries multiple wavelength bands, to N wavelength-specific output ports that are coupled to a set of N reflectors. A set of variable optical attenuators (VOAs) is coupled to outputs of the MZ lattice filters in the binary tree, and is controllable to selectively add loss to the outputs, so that only a single favored wavelength band, which is associated with a favored reflector in the set of N reflectors, lases at any given time. An output waveguide is optically coupled to the lasing cavity.

Abstract: The disclosed embodiments provide a tunable laser that includes a set of M reflective silicon optical amplifiers (RSOAs) and a set of N narrow-band reflectors. It also includes a silicon-photonic optical switch, having M amplifier ports, which are coupled through a set of M optical waveguides to the set of M RSOAs, and N reflector ports, which are coupled to the set of N narrow-band reflectors. The tunable laser also includes a switching mechanism that facilitates coupling at least one selected amplifier port from the M amplifier ports with a selected reflector port from the N reflector ports, thereby causing an RSOA coupled to the selected amplifier port to form a lasing cavity with a narrow-band reflector coupled to the selected reflector port. The tunable laser also includes a laser output, which is optically coupled to the lasing cavity.

Abstract: An integrated circuit that includes a wavelength-filter layer stack (which may include silicon oxynitride) and an optical substrate (such as a silicon-on-insulator platform) is described. During operation, an optical signal received from an optical fiber or an optical waveguide is wavelength filtered into a set of wavelength-filter optical waveguides by an optical multiplexer/demultiplexer (such as an Echelle grating and/or an array waveguide grating) in the wavelength-filter layer stack. Then, wavelength-filtered optical signals are optically coupled to the optical substrate, where they are received using photodetectors. Alternatively, modulators in the optical substrate modulate wavelength-filtered modulated optical signals, which are then optically coupled to the set of wavelength-filter optical waveguides in the wavelength-filter layer stack.

Abstract: An optical modulator is described. This optical modulator may be implemented using silicon-on-insulator (SOI) technology. In particular, a semiconductor layer in an SOI platform may include a photonic crystal having a group velocity of light that is less than that of the semiconductor layer. Moreover, an optical modulator (such as a Mach-Zehnder interferometer) may be implemented in the photonic crystal with a vertical junction in the semiconductor layer. During operation of the optical modulator, an input optical signal may be split into two different optical signals that feed two optical waveguides, and then subsequently combined into an output optical signal. Furthermore, during operation, time-varying bias voltages may be applied across the vertical junction in the optical modulator using contacts defined along a lateral direction of the optical modulator.

Abstract: An optical modulator is described. This optical modulator may be implemented using silicon-on-insulator (SOI) technology. In particular, a semiconductor layer in an SOI platform may include a photonic crystal having a group velocity of light that is less than that of the semiconductor layer. Moreover, an optical modulator (such as a Mach-Zehnder interferometer) may be implemented in the photonic crystal with a vertical junction in the semiconductor layer. During operation of the optical modulator, an input optical signal may be split into two different optical signals that feed two optical waveguides, and then subsequently combined into an output optical signal. Furthermore, during operation, time-varying bias voltages may be applied across the vertical junction in the optical modulator using contacts defined along a lateral direction of the optical modulator.