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 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 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 fully integrated avalanche photodiode receiver and manufacturing method thereof are described herein. A photonic device includes a silicon-on-insulator (SOI) substrate with a buried oxide (BOX) layer therein, an avalanche photodiode integrated with the SOI substrate, a capacitor integrated with the SOI substrate, a resistor integrated with the SOI substrate, and silicon passive waveguides as well as bonding pads integrated with the SOI substrate.

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 compensated photonic device structure and fabrication method thereof are described herein. A photonic device may include a silicon-on-insulator (SOI) substrate with a buried oxide (BOX) layer therein, a Si waveguide and an n-type contact layer formed on the BOX layer, a Si multiplication layer disposed on the n-type contact layer, a p-type Si charge layer disposed on the Si multiplication layer, a germanium (Ge) absorption layer disposed on the p-type Si charge layer, a p-type contact layer disposed on the Ge absorption layer, and a metal layer disposed on the p-type contact layer. A compensated region may be formed between the p-type Si charge layer and the Ge absorption layer with a portion of the compensated region in the p-type Si charge layer and another portion of the compensated region in the Ge absorption layer.

Abstract: An imprinting method for forming an integrated optical coupling device on wafer level may include: providing a substrate, with a reflection coating disposed thereon; providing an imprinting mold, with void regions shaped according to a designed lens profile; forming a molding material on the substrate; pressing the imprinting mold on the molding material on the substrate; curing the molding material into a cured molding material; removing the imprinting mold; depositing an anti-reflection film on the cured molding material; and dicing to form an integrated optical coupling device.

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: An optical coupler structure may include a substrate, a waveguide section and an anchored cantilever section. The substrate may include a main body and a sub-pillar structure formed on the main body. The waveguide section may be disposed on the substrate, and may include a core waveguide of a first material surrounded by a cladding layer of a second material. The anchored cantilever section may be disposed on the sub-pillar structure on the substrate, which may be configured to support the cantilever section and separate the cantilever section from the main body of the substrate. The anchored cantilever section may include a multi-stage inverse taper core waveguide and a cladding layer, of the second material, which surrounds the multi-stage inverse taper core waveguide.

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: 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: An optical package for providing efficient coupling between a distributed feedback laser diode (DFB-LD) and a silicon photonic integrated-circuit chip (Si PIC) edge couplers with low return loss, as well as variations thereof, is described. The optical package may include a DFB-LD, a Si PIC, a single mode fiber or fiber array assembly, a lens and a spacer. The Si PIC may include an input edge coupler and an output edge coupler. The single mode fiber or fiber array assembly may be aligned to the output edge coupler. The lens may be disposed between the DFB-LD and the input edge coupler, and may be configured to minimize a mismatch between an output spot size of the DFB-LD and a spot size of the input edge coupler of the Si PIC. The spacer may be bonded to a facet of the input edge coupler with an index matching fluid.

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.