Abstract: Processes and devices for continuous compositional grading in photodetectors and electro-absorption modulators (EAM) are provided. An example photodetector includes a multi-layered structure comprising a collector region, an absorber region, a grading layer, and a peripheral layer, all aligned along a detection axis. The grading layer, positioned adjacent to the absorber region, includes multiple sub-layers that define a continuous compositional grading to facilitate smooth carrier transport and reduce recombination. Similarly, an example electro-absorption modulator (EAM) device includes a waveguide mesa formed on a semiconductor substrate, comprising a multi-quantum well (MQW) core layer, upper and lower near-core cladding layers, and upper and lower central cladding layers. The EAM device features both upper and lower grading layers, each positioned between the near-core cladding layers and the adjacent central cladding layers.

Abstract: Some embodiments of the present invention are directed to a tunnel junction for a vertical-cavity surface-emitting laser (VCSEL) that controls optical and current confinement within the VCSEL. The tunnel junction may define an electrical current injection area and an optical aperture for the VCSEL and may include a heavily p++ doped p-type material and a heavily n++ doped n-type material disposed on the p-type material. At least a portion of the outer edges of the n-type material are etched such that the n-type material has a cross-sectional area that is less than a cross-sectional area of the p-type material. By removing a portion of n-type material near the outer edge of the tunnel junction, a sloped effective refractive index is formed, and an effective area of the tunnel junction is changed, which increases the overlap of the current density and the optical field of the VCSEL.

Abstract: Some embodiments of the present invention are directed to a multi-layer oxide aperture for a VCSEL. The oxide aperture may include multiple layers having different aluminum fractions that may reduce a spectral width of the VCSEL while maintaining longitudinal confinement. The oxide aperture may be formed from a mirror layer of the VCSEL proximate an active region. The mirror layer may include first epitaxial layers closest to the active region having a first aluminum fraction selected to longitudinally confine the optical field of the VCSEL. The mirror layer may include second epitaxial layers that have a second aluminum fraction low enough to prevent substantial oxidation of the second epitaxial layers. Additionally, the mirror layer may include third epitaxial layers that have a third aluminum fraction greater than the first and second aluminum fractions. The third epitaxial layers may be oxidized to form the oxide aperture.

Abstract: Some embodiments of the present invention are directed to a mode-filtered VCSEL having a multi-layer oxide aperture for high-bandwidth and side-mode suppression. The oxide aperture may include multiple layers having different aluminum fractions configured to increase an SMSR of the VCSEL while maintaining longitudinal confinement. The oxide aperture may be formed from a mirror layer of the VCSEL proximate an active region. The mirror layer may include first epitaxial layers closest to the active region having a first aluminum fraction selected to longitudinally confine the optical field of the VCSEL. The mirror layer may include second epitaxial layers having a second aluminum fraction low enough to prevent substantial oxidation of the second epitaxial layers. Additionally, the mirror layer may include third epitaxial layers having a third aluminum fraction greater than the first and second aluminum fractions. The third epitaxial layers may be oxidized to form the oxide aperture.

Abstract: Processes for continuous compositional grading for realization of low charge carrier barriers in electro-optical heterostructure semiconductor devices are provided. An example process includes forming, onto one or more semiconductor layers of an electro-optical semiconductor device, a first semiconductor layer associated with a first bandgap value and forming, onto the first semiconductor layer, a grading layer associated with a continuous compositional grading. The example method further includes forming, onto the grading layer, a second semiconductor layer associated with a second bandgap value. The second bandgap value is different than the first bandgap value.

Abstract: Systems and methods are described herein for an electro-absorption modulator (EAM) device. An example EAM device comprises an optical waveguide comprising a waveguide core configured to facilitate a propagation of an optical signal therethrough; a segmented traveling wave electrode structure comprising electrode segments disposed on the optical waveguide; and an electrical transmission line operatively coupled to the electrode segments via conducting bridges, wherein the electrical transmission line is configured to facilitate a propagation of an electrical signal therethrough, wherein the electrode segments are configured to overcome bandwidth and extinction ratio constraints of a lumped EAM.

Abstract: Systems and methods are described herein for an electro-absorption modulator (EAM) device. An example EAM device comprises an optical waveguide comprising a waveguide core configured to facilitate propagation of an optical signal therethrough; a segmented structure comprising diode segments disposed on the waveguide; and a differential electrical transmission line operatively coupled to the diode segments. The electrical transmission line includes a first transmission rail and a second transmission rail, and the electrical transmission line is configured to facilitate propagation of an electrical signal therethrough. The EAM device is configured for operation by a differential radio frequency (RF) source that is configured to supply the electrical signal to the EAM device, and the EAM device is formed on a semi-insulating substrate.

Abstract: Multiple methods are provided for fiber optic welding on a photonic integrated circuit (PIC). An example method includes providing a PIC, forming an attachment surface on the PIC configured to receive an optical fiber. The method further includes disposing at least a portion of the optical fiber on the attachment surface. The method may then include welding the optical fiber to secure the optical fiber with respect to the attachment surface. The attachment surface may be comprised of substantially the same material as an outer portion of the optical fiber and may result in a homogenous weld securing and connecting the optical fiber to the PIC.

Abstract: Photodetectors configured to detect light in a particular wavelength range and including a quaternary material are described herein. In some embodiments, the present invention may be directed to a photodetector that includes a collector material that is substantially transparent to the particular wavelength range and a quaternary material adjacent to the collector material, where the quaternary material functions as an absorber material and is lattice-matched to the collector material. A conduction band difference between the collector material and the quaternary material may be approximately zero. Additionally, or alternatively, the photodetector may include a peripheral layer adjacent to the quaternary material, where the peripheral layer is doped with carbon. In some embodiments, the photodetector may include an optical window configured for use with a multi-mode optical fiber.

Abstract: Processes for continuous compositional grading for realization of low charge carrier barriers in electro-optical heterostructure semiconductor devices are provided. An example process includes forming, onto one or more semiconductor layers of an electro-optical semiconductor device, a first semiconductor layer associated with a first bandgap value and forming, onto the first semiconductor layer, a grading layer associated with a continuous compositional grading. The example method further includes forming, onto the grading layer, a second semiconductor layer associated with a second bandgap value. The second bandgap value is different than the first bandgap value.

Abstract: Bi-directional quantum interconnects are provided that include a first communication module and a second communication module. The first communication module includes a first quantum transmitter and a first quantum receiver, and the second communication module includes a second quantum transmitter and a second quantum receiver. The example interconnect further includes a first communication medium communicably coupling the first communication module and the second communication module such that communication is provided between the first quantum transmitter and the second quantum receiver and between the second quantum transmitter and the first quantum receiver via the first communication medium. The first quantum transmitter and the second quantum transmitter generate qubits having first and second quantum characteristics, respectively, to allow for bi-directional quantum communication over a common channel.

Abstract: VCSELs designed to emit light at a characteristic wavelength in a wavelength range of 910-2000 nm and formed on a silicon substrate are provided. Integrated VCSEL systems are also provided that include one or more VCSELs formed on a silicon substrate and one or more electrical, optical, and/or electro-optical components formed and/or mounted onto the silicon substrate. In an integrated VCSEL system, at least one of the one or more electrical, optical, and/or electro-optical components formed and/or mounted onto the silicon substrate is electrically or optically coupled to at least one of the one or more VSCELs on the silicon substrate. Methods for fabricating VCSELs on a silicon substrate and/or fabricating an integrated VCSEL system are also provided.

Abstract: A tunable vertical-cavity surface-emitting laser (VCSEL) is provided. The VCSEL includes a VCSEL emission structure, piezoelectric material, and a piezoelectric electrode. The VCSEL emission structure includes a first reflector; a second reflector; and an active cavity material structure disposed between the first and second reflectors. The active cavity material structure includes an active region. The piezoelectric material is mechanically coupled to the VCSEL emission structure such that when the piezoelectric material experiences a mechanical stress, the mechanical stress is transferred to the active cavity material structure of the VCSEL emission structure. The piezoelectric electrode is designed to cause an electric field within the piezoelectric material.

Abstract: High bandwidth (e.g., > 100 GHz) modulators and methods of fabricating such are provided. An EAM comprises a waveguide mesa comprising a continuous multi-quantum well (MQW) layer; a plurality of electrode segments disposed on the waveguide mesa; and a microstrip transmission line disposed on an insulating material layer and in electrical communication with the plurality of electrode segments via conducting bridges. The waveguide mesa comprises alternating active sections and passive sections. An electrode segment of the plurality of electrodes is disposed on a respective one of the active sections. Portions of the continuous MQW layer disposed in each of the active sections having an energy gap defining an active energy gap value. Portions of the continuous MQW layer disposed in each of the passive sections having an energy gap defining an passive energy gap value. The active energy gap value is less than the passive energy gap value.

Abstract: Methods for forming an at least partially oxidized confinement layer of a semiconductor device and corresponding semiconductor devices are provided. The method comprises forming two or more layers of a semiconductor device on a substrate. The layers include an exposed layer and a to-be-oxidized layer. The to-be-oxidized layer is disposed between the substrate and the exposed layer. The method further comprises etching, using a masking process, a pattern of holes that extend through the exposed layer at least to a first surface of the to-be-oxidized layer. Each hole of the pattern of holes extends in a direction that is transverse to a level plane that is parallel to the first surface of the to-be-oxidized layer. The method further comprises oxidizing the to-be-oxidized layer through the pattern of holes by exposing the two or more layers of the semiconductor device to an oxidizing gas to form a confinement layer.

Abstract: VCSELs designed to emit light at a characteristic wavelength in a wavelength range of 910-2000 nm and formed on a silicon substrate are provided. Integrated VCSEL systems are also provided that include one or more VCSELs formed on a silicon substrate and one or more electrical, optical, and/or electro-optical components formed and/or mounted onto the silicon substrate. In an integrated VCSEL system, at least one of the one or more electrical, optical, and/or electro-optical components formed and/or mounted onto the silicon substrate is electrically or optically coupled to at least one of the one or more VSCELs on the silicon substrate. Methods for fabricating VCSELs on a silicon substrate and/or fabricating an integrated VCSEL system are also provided.

Abstract: A tunable vertical-cavity surface-emitting laser (VCSEL) is provided. The VCSEL includes a VCSEL emission structure, piezoelectric material, and a piezoelectric electrode. The VCSEL emission structure includes a first reflector; a second reflector; and an active cavity material structure disposed between the first and second reflectors. The active cavity material structure includes an active region. The piezoelectric material is mechanically coupled to the VCSEL emission structure such that when the piezoelectric material experiences a mechanical stress, the mechanical stress is transferred to the active cavity material structure of the VCSEL emission structure. The piezoelectric electrode is designed to cause an electric field within the piezoelectric material.

Abstract: A vertical-cavity surface-emitting laser (VCSEL) and method of fabrication thereof is provided. The VCSEL includes a mesa structure disposed on a substrate. The mesa structure has a first reflector stack, a second reflector stack, and an active region disposed between the first and second reflector stacks. The active region is configured to cause the VCSEL to emit light having a characteristic wavelength of 910 nanometers. The active region includes alternating layers of quantum wells and barriers, the quantum wells having high indium content (up to 18%). The VCSEL features a first contact layer disposed at least partially on a surface of the mesa structure and configured to serve as an electrical signal layer and a second contact layer disposed at least partially about the mesa structure and configured to serve as an electrical ground.

Abstract: An electro-optical link is provided. In an example embodiment, the electro-optical link includes a number of vertical cavity surface emitting lasers (VCSELs); one or more drivers that operate the VCSELs such that each of the VCSELs selectively emits an optical signal; one or more multiplexers that multiplex a number of optical signals into an optical fiber, each optical signal emitted by one of the VCSELs; and one or more optical fibers. At least two optical signals are multiplexed into each optical fiber of the one or more optical fibers. In some example configurations eight or sixteen optical signals are multiplexed into one optical fiber.