Abstract: Various embodiments of a monolithic transceiver are described, which may be fabricated on a semiconductor substrate. The monolithic transceiver includes a coherent receiver module (CRM), a coherent transmitter module (CTM), and a local oscillation splitter to feed a local oscillation to the CRM and the CTM with a tunable power ratio. The monolithic transceiver provides tunable responsivity by employing avalanche photodiodes (APDs) for opto-electrical conversion. The monolithic transceiver also employs a polarization beam rotator-splitter (PBRS) and a polarization beam rotator-combiner (PBRC) for supporting modulation schemes including polarization multiplexed quadrature amplitude modulation (PM-QAM) and polarization multiplexed quadrature phase shift keying (PM-QPSK).

Abstract: Various embodiments of a monolithic electro-optical (E-O) modulator are described herein. The monolithic E-O modulator may include a phase shifter having a suspended structure. The suspended structure may be realized by partially or completely removing silicon material underneath the active area of the phase shifter to form a void in the bulk silicon substrate supporting the phase shifter. The suspended structure may be utilized to result in a lower radio-frequency loss and an effective group refractive index of the phase shifter that is closer to the refractive index of silicon waveguides or optical fibers, both advantageous to enhancing the performance of the E-O modulator such as a higher operating bandwidth.

Abstract: Various embodiments of a photonic integrated circuit (PIC) are described herein. A PIC, functioning as a coherent receiver, may include optical components such as an optical coupler, a directional coupler, a beam splitter, a polarizing beam rotator-splitter, a variable optical attenuator, a monitor photodiode, 90-degree hybrid mixer, and a waveguide photodiode. The PIC may also include electrical components such as an electrode, a capacitor, a resistor and a Zener diode.

Abstract: Various embodiments of a compensated photonic device structure and fabrication method thereof are described herein. In one aspect, a photonic device may include a substrate and a functional layer disposed on the substrate. The substrate may be made of a first material and the functional layer may be made of a second material that is different from the first material. The photonic device may also include a compensation region formed at an interface region between the substrate and the functional layer. The compensation region may be doped with compensation dopants such that a first carrier concentration around the interface region of function layer is reduced and a second carrier concentration in a bulk region of functional layer is reduced.

Abstract: Various embodiments of an integrated polarization rotator-splitter/combiner apparatus are described. An integrated polarization rotator-splitter apparatus may include an input waveguide section, a polarization rotator section, a polarization splitter section and an outgoing waveguide section, which can also be reversely connected as a polarization rotator-combiner.

Abstract: A compact and highly efficient coupling structure for coupling between DFB-LD and Si PIC edge coupler with suppressed return loss may include a DFB-LD, a Si PIC comprising at least one input edge coupler and at least one output edge coupler, a silica cover lid disposed on the Si PIC and aligned edge to edge with the Si PIC, a single-mode fiber aligned to the at least one output edge coupler of the Si PIC, a lens disposed between the DFB-LD and the at least one input edge coupler of the Si PIC, and an isolator bonded to a facet of the at least one input edge coupler with a first volume of an index matching fluid. The lens may be configured to minimize a mismatch between an output spot size of the DFB-LD and a spot size of the at least one input edge coupler of the Si PIC.

Abstract: A ring optical modulator includes a SOI substrate, including at least first and second top silicon layers, and a silicon-based ring resonator formed on the SOI substrate. The silicon-based ring resonator includes first and second top silicon layers, a thin dielectric gate layer disposed between the top silicon layers, first and second electric contacts, and first rib-type waveguide and ring-shape rib-type waveguide formed on the second top silicon layer. The thin dielectric layer includes a first side in contact with the first top silicon layer and a second side in contact with the second top silicon layer. With electric signals applied on the electric contacts, free carriers accumulate, deplete or invert within the top silicon layers on the first and second sides of the thin dielectric gate layer beneath the ring-shape rib-type waveguide, simultaneously, and a refractive index of the ring-shape rib-type waveguide confining optical fields is modulated.

Abstract: Avalanche photodiodes (APDs) having at least one top stressor layer disposed on a germanium (Ge) absorption layer are described herein. The top stressor layer can increase the tensile strain of the Ge absorption layer, thus extending the absorption of APDs to longer wavelengths beyond 1550 nm. In one embodiment, the top stressor layer has a four-layer structure, including an amorphous silicon (Si) layer disposed on the Ge absorption layer; a first silicon dioxide (SiO2) layer disposed on the amorphous Si layer, a silicon nitride (SiN) layer disposed on the first SiO2 layer, and a second SiO2 layer disposed on the SiN layer. The Ge absorption layer can be further doped by p-type dopants. The doping concentration of p-type dopants is controlled such that a graded doping profile is formed within the Ge absorption layer to decrease the dark currents in APDs.

Abstract: Various embodiments of a compensated photonic device structure and fabrication method thereof are described herein. In one aspect, a photonic device may include a substrate and a functional layer disposed on the substrate. The substrate may be made of a first material and the functional layer may be made of a second material that is different from the first material. The photonic device may also include a compensation region formed at an interface region between the substrate and the functional layer. The compensation region may be doped with compensation dopants such that a first carrier concentration around the interface region of function layer is reduced and a second carrier concentration in a bulk region of functional layer is reduced.

Abstract: Various embodiments of a novel structure of a Ge/Si avalanche photodiode with an integrated heater, as well as a fabrication method thereof, are provided. In one aspect, a doped region is formed either on the top silicon layer or the silicon substrate layer to function as a resistor. When the environmental temperature decreases to a certain point, a temperature control loop will be automatically triggered and a proper bias is applied along the heater, thus the temperature of the junction region of a Ge/Si avalanche photodiode is kept within an optimized range to maintain high sensitivity of the avalanche photodiode and low bit-error rate level.

Abstract: A high-speed germanium on silicon (Ge/Si) avalanche photodiode may include a substrate layer, a bottom contact layer disposed on the substrate layer, a buffer layer disposed on the bottom contact layer, an electric field control layer disposed on the buffer layer, an avalanche layer disposed on the electric field control layer, a charge layer disposed on the avalanche layer, an absorption layer disposed on the charge layer, and a top contact layer disposed on the absorption layer. The electric field contact layer may be configured to control an electric field in the avalanche layer.

Abstract: An integrated optical coupling device may include a substrate, a coating layer disposed on the substrate, and a prism disposed on the coating layer. The prism may include a first surface and a second surface. The integrated optical coupling device may also include a first lens disposed on the first surface of the prism, a second lens disposed on the second surface of the prism, and an anti-reflection coating layer disposed on the first lens and the second lens.

Abstract: Various structures of an electro-optic device and fabrication methods thereof are described. A fabrication method is provided to fabricate an electro-optic device which may include a silicon-based rib-waveguide modulator which includes a first top silicon layer, having a first doped region that is at least partially doped with dopants of a first conducting type, a second top silicon layer, having a second doped region that is at least partially doped with dopants of a second conducting type, and a thin dielectric gate layer disposed between the first top silicon layer and the second top silicon layer. The second doped region may be at least in part directly over the first doped region. The modulator may also include a rib waveguide formed on the second top silicon layer, a first electric contact formed on the first top silicon layer, and a second electric contact formed on the second top silicon layer.

Abstract: Various embodiments of a germanium-on-silicon (Ge—Si) avalanche photodiode are provided. In one aspect, the Ge—Si avalanche photodiode utilizes a silicon carrier-energy-relaxation layer to reduce the energy of holes drifting into absorption layer where the absorption material has lower ionization threshold, thereby suppressing multiplication noise and increasing the gain-bandwidth product of the avalanche photodiode.

Abstract: Various embodiments of a photonic device and fabrication method thereof are described herein. A device may include a substrate, a bottom contact layer, a current confinement layer, an intrinsic layer, an absorption layer, and a top contact layer. The bottom contact layer may be of a first polarity and may be disposed on the substrate. The current confinement layer may be disposed on the bottom contact layer. The intrinsic layer may be disposed on the current confinement layer. The absorption layer may be disposed on the intrinsic layer. The top contact layer may be of a second polarity and may be disposed on the absorption layer. The second polarity is opposite to the first polarity.

Abstract: Various embodiments of a novel method and design for coupling optical signals from a lens array to a fiber array subassembly with locking capability in a pluggable form factor are provided. Optical signals vertically emitted from a vertical-cavity surface-emitting laser (VCSEL) array on a printed circuit board (PCB) are coupled into an optical coupling lens array, which are then coupled into a fiber array subassembly parallel to the PCB. A locking device in a pluggable form factor provides means for mating and locking between the lens array and the fiber array subassembly, thereby achieving good coupling and locking between the fiber array subassembly and lens array.

Abstract: Embodiments of the present disclosure provide a high-speed silicon modulator without the microwave mode conversion and provide 50-ohm impedance matching to drivers simultaneously. In one aspect, a device may include an input waveguide region, an optic splitter, two optic phase shifters, an optic splitter, and an output waveguide. The device may include two curved waveguides. Either or both of the curved waveguides may have specially doped regions including PN junctions or MOS capacitors. The PN junctions or MOS capacitors may be alternatively connected to both slots of a coplanar waveguide forming the electrodes.

Abstract: Avalanche photodiodes (APDs) having at least one top stressor layer disposed on a germanium (Ge) absorption layer are described herein. The top stressor layer can increase the tensile strain of the Ge absorption layer, thus extending the absorption of APDs to longer wavelengths beyond 1550 nm. In one embodiment, the top stressor layer has a four-layer structure, including an amorphous silicon (Si) layer disposed on the Ge absorption layer; a first silicon dioxide (SiO2) layer disposed on the amorphous Si layer, a silicon nitride (SiN) layer disposed on the first SiO2 layer, and a second SiO2 layer disposed on the SiN layer. The Ge absorption layer can be further doped by p-type dopants. The doping concentration of p-type dopants is controlled such that a graded doping profile is formed within the Ge absorption layer to decrease the dark currents in APDs.

Abstract: Avalanche photodiodes (APDs) having at least one top stressor layer disposed on a germanium (Ge)-containing absorption layer are described herein. The top stressor layer can increase the tensile strain of the Ge-containing absorption layer, thus extending the absorption of APDs to longer wavelengths beyond 1550 nm. In one embodiment, the top stressor layer has a four-layer structure, including an amorphous silicon (Si) layer disposed on the Ge-containing absorption layer; a first silicon dioxide (SiO2) layer disposed on the amorphous Si layer, a silicon nitride (SiN) layer disposed on the first SiO2 layer, and a second SiO2 layer disposed on the SiN layer. The Ge-containing absorption layer can be further doped by p-type dopants. The doping concentration of p-type dopants is controlled such that a graded doping profile is formed within the Ge-containing absorption layer to decrease the dark currents in APDs.

Abstract: Avalanche photodiodes having special lateral doping concentration that reduces dark current without causing any loss of optical signals and method for the fabrication thereof are described. In one aspect, an avalanche photodiode comprises: a substrate, a first contact layer coupled to at least one metal contract of a first electrical polarity, an absorption layer, a doped electric control layer having a central region and a circumferential region surrounding the central region, a multiplication layer having a partially doped central region, and a second contract layer coupled to at least one metal contract of a second electrical polarity. Doping concentration in the central section is lower than that of the circumferential region. The absorption layer can be formed by selective epitaxial growth.