Abstract: Vector and matrix multiplications can be accomplished in photonic circuitry by coherently combining light that has been optically modulated, in amplitude and/or phase, in accordance with the vector and matrix components. Disclosed are various beneficial photonic circuit layouts characterized by loss- and delay-balanced optical paths. In various embodiments, loss balancing across paths is achieved with suitable optical coupling ratios and balanced numbers of waveguide crossings (using dummy crossings where needed) across the paths. Delays are balanced in some embodiments with geometrically delay-matched optical paths.

Abstract: Vector and matrix multiplications can be accomplished in photonic circuitry by coherently combining light that has been optically modulated, in amplitude and/or phase, in accordance with the vector and matrix components. Disclosed are various beneficial photonic circuit layouts characterized by loss- and delay-balanced optical paths. In various embodiments, loss balancing across paths is achieved with suitable optical coupling ratios and balanced numbers of waveguide crossings (using dummy crossings where needed) across the paths. Delays are balanced in some embodiments with geometrically delay-matched optical paths.

Abstract: An optical resonant modulator based on coupling modulation, comprising a resonant structure with an embedded Mach-Zehnder interferometer that is differentially driven to induced amplitude modulation at the output port. The principle of coupling modulation enables high data/baud rates to be achieved in a photonic integrated circuit, e.g. silicon, footprint that is considerably smaller than that of a conventional traveling-wave Mach-Zehnder modulator, in particular by utilizing space saving features, such as ring resonator phase shifters and bend waveguide arms.

Abstract: An optical resonant modulator based on coupling modulation, comprising a resonant structure with an embedded Mach-Zehnder interferometer that is differentially driven to induced amplitude modulation at the output port. The principle of coupling modulation enables high data/baud rates to be achieved in a photonic integrated circuit, e.g. silicon, footprint that is considerably smaller than that of a conventional traveling-wave Mach-Zehnder modulator, in particular by utilizing space saving features, such as ring resonator phase shifters and bend waveguide arms.

Abstract: A low loss high extinction ratio on-chip polarizer is disclosed. The polarizer includes an input waveguide taper having an outer waveguiding region that widens in the direction of light propagation along at least a portion of the taper length, and a core waveguiding region that narrows in the direction of light propagation along at least a portion of the taper length, so as to selectively squeeze out light of undesired modes into the outer regions while preserving light of a desired mode in the waveguide core. An output filter section is provided to prevent light from reentering the output waveguide after being squeezed out. An integrated light absorber/deflector may be coupled to the outer waveguiding regions.

Abstract: Conventional integrated optical amplifiers, which combine different types of platforms, e.g. silicon photonic integrated circuit for the device layer, and a Group III-V material for the gain medium, typically include a curved waveguide extending through the gain medium coupled to waveguides in the main device layer. Unfortunately, the radius of curvature of the curved waveguide becomes a limiting factor for both size and amplification. Accordingly, an optical amplifier which eliminates the need for the curved waveguide by including a coupler for splitting an input optical signal into two sub-beams, for passage through the gain medium, and a reflector, such as a U-turn, for reflecting or redirecting the two sub-beams back through the gain medium to the coupler for recombination, would be a welcome improvement. A phase tuner may also be provided to ensure coherence cancellation between the two sub-beams to maximize output and minimize back reflection without requiring an isolator.

Abstract: A compact, low-loss and wavelength insensitive Y-junction for submicron silicon waveguides. The design was performed using FDTD and particle swarm optimization (PSO). The device was fabricated in a 248 nm CMOS line. Measured average insertion loss is 0.28±0.02 dB across an 8-inch wafer. The device footprint is less than 1.2 ?m×2 ?m, orders of magnitude smaller than MMI and directional couplers.

Abstract: An optical circuit capable of operating as a 90° optical hybrid includes a phase-symmetric optical splitter and a 90° optical splitter, and two 2×2 optical couplers as optical combiners. The input ports of the optical combiners and the output ports of the optical splitters face a common area therebetween, with the optical splitters interposed between optical combiners as viewed along the circumference of the common area. The output ports of each optical splitter is connected to closest input ports of the optical combiners with optical waveguides of a same length. The length of the waveguides may be minimized when the optical couplers and the optical splitters are disposed in a cross-like configuration.

Abstract: In Mach-Zehnder interferometer (MZI) based modulators (MZM) input laser light comes in from one side, gets split into two MZI arms, then recombined at an opposite side. Each MZI arm may be phase or intensity modulated depending on the set phase offset, whereby coherent or intensity modulation may be performed which can later be de-coded by a receiver. Ring resonator type modulators (RRM) are compact; however, their phase response is nonlinear, normally limiting their application in coherent phase modulation. However, a combined MZI RRM overcomes the shortcomings of the prior art by providing a novel structure and driving scheme for use with semiconductor photonics that takes advantage of the compactness of ring modulators and the linearity of MZI by setting the ring resonators to resonate at the input laser light wavelength.

Abstract: A dual-differential optical modulator includes two optical waveguide arms, each including one or more phase modulating p/n junctions. The p/n junctions in each waveguide arm are electrically coupled between a same pair of single-ended transmission lines so as to be differentially push-pull modulated when the transmission line pair is connected to a differential driver. Either cathode or anode electrodes of the p/n junctions are AC coupled to the transmission lines and DC biased independently on the transmission line signals.

Abstract: An integrated polarization splitter and rotator (PSR) employs the TE0 and TE1 modes of propagating light, rather than the TE0 and TM0 modes used in conventional prior art PSR. The integrated PSR exhibits appreciably flatter wavelength response because it does not require a directional coupler to de-multiplex incoming polarizations. The PSR allows tuning of the TM0 loss to reduce polarization dependent loss (PDL). This integrated polarization splitter and rotator is applicable to all integrated platforms including Silicon-on-Insulator (SOI) and III-V semiconductor compound systems. The PSR may be very compact (12×2 ?m2), and provides low loss (<0.3 dB across the C-band) and ultra-broadband operation. The PSR also affords better control of polarization dependent losses.

Abstract: Conventionally, wavelength locking and monitoring has been achieved used various components, including calibrated etalon filters, gratings, and arrays of color filters, which offer fairly bulky solutions that require complicated controls. An improved on-chip wavelength monitor comprises: a combination comb filter comprising a plurality of comb filters, each for receiving a test beams, and each comb filter including a substantially different FSR, e.g. 10× to 20× the next closest FSR. A controller dithers a phase tuning section of each comb filter to generate a maximum or minimum output in a corresponding photodetector indicative of the wavelength of the test signal.

Abstract: A multimode interference (MMI) coupler with an MMI region of curved edges, and a method of design and manufacturing by using a computerized optimization algorithm to determine a favorable set of segment widths for the MMI region for a predefined set of coupler design parameters.

Abstract: A semiconductor-based Mach-Zehnder modulator (MZM) is configured for push-pull bias dithering to control the MZM bias at a desired set point. When two such MZM modulators are connected in parallel to form an IQ modulator, bias settings for both MZMs and the IQ bias may be controlled from an output of the IQ modulator to minimize both the IQ offset and the quadrature error of the output signal constellation even for non-ideal MZMs with low extinction ratios.

Abstract: A photonic chip including an integrated optoelectronic device is flip-chip mounted to a carrier. The optoelectronic device is provided with a 3D ground cage as a shield for stray EM radiation. The 3D ground cage is formed by a device ground electrode partially enclosing the optoelectronic device on a face of the chip, a carrier ground electrode disposed opposite to the device ground electrode, and a plurality of metal pillars therebetween at least partially surrounding the optoelectronic device. The optoelectronic device may be an OE converter of an integrated optical receiver. The optoelectronic device may also be an EO converter of an integrated optical transmitter.

Abstract: A method and structure are provided for testing photonic circuits with integrated optical mixers having idle ports. A test port is provided for coupling test light into one or more idle ports of the mixer. Light exiting output ports of the mixer may be measured with photodetectors. Phase errors of optical hybrids may be determined by using waveguides of different lengths to inject test light into two input ports of the mixer and scanning the test wavelength. The method and structure may be used for on-wafer and off-wafer measurements of integrated photonic circuits implementing coherent optical receivers.

Abstract: A MOSCAP phase adjuster includes two conductive regions with a thin insulating region therebetween, where charge is accumulated or depleted. In conventional MOSCAP modulators, the conductive and insulating regions are superposed layers, extending horizontally parallel to the substrate, which limits waveguide design and mode confinement, resulting in reduced phase shift performance. An improved MOSCAP phase adjuster and method of fabricating a MOSCAP phase adjuster includes depositing the material for the second conductive region beside and over top of the first conductive region after oxidation, and selectively etching the material to form the second conductive region.

Abstract: In Mach-Zehnder interferometer (MZI) based modulators (MZM) input laser light comes in from one side, gets split into two MZI arms, then recombined at an opposite side. Each MZI arm may be phase or intensity modulated depending on the set phase offset, whereby coherent or intensity modulation may be performed which can later be de-coded by a receiver. Ring resonator type modulators (RRM) are compact; however, their phase response is nonlinear, normally limiting their application in coherent phase modulation. However, a combined MZI RRM overcomes the shortcomings of the prior art by providing a novel structure and driving scheme for use with semiconductor photonics that takes advantage of the compactness of ring modulators and the linearity of MZI by setting the ring resonators to resonate at the input laser light wavelength.

Abstract: Practical silicon-based light sources are still missing, despite the progress in germanium lasers, because both silicon and germanium are indirect-band semiconductors and inefficient at light generation. A tunable and single mode external cavity laser comprising: a gain medium for generating light between a reflective surface at one end of the gain medium; and a wavelength selective reflector at the other end of a laser cavity. A splitter disposed in the laser cavity includes an input port optically coupled to the gain medium, an input/output port optically coupled to the wavelength selective reflector, and an output port for outputting laser light at selected wavelengths. The wavelength selective reflector reflects light of one or more selected periodic wavelengths back to the gain medium via the input/output port, and passes light of non-selected wavelengths out of the laser cavity.

Abstract: Conventionally, wavelength locking and monitoring has been achieved used various components, including calibrated etalon filters, gratings, and arrays of color filters, which offer fairly bulky solutions that require complicated controls. An improved on-chip wavelength monitor comprises: a combination comb filter comprising a plurality of comb filters, each for receiving a test beams, and each comb filter including a substantially different FSR, e.g. 10× to 20× the next closest FSR. A controller dithers a phase tuning section of each comb filter to generate a maximum or minimum output in a corresponding photodetector indicative of the wavelength of the test signal.