Abstract: Disclosed are a mixed-reality optical waveguide-based combiner apparatus that includes stacked plates of reflective optical elements (ROEs) and associated methods of fabrication. ROEs in the plates of the waveguide combiner share a commonly shaped and sized footprint and are aligned in the stack. A top plate in the stack of plates includes an input-coupler, such as a prism, for in-coupling light for virtual images from a display engine into the waveguide combiner. The top plate also includes a top ROE comprising a cascaded array of mirror elements in a waveguide that horizontally expands an exit pupil of the virtual images and couples the light to a corresponding bottom ROE, disposed in a bottom plate in the stack, comprising a cascaded array of mirror elements in a waveguide. The bottom ROE couples the virtual image light to an output coupler in the bottom plate which out-couples light from the waveguide combiner.

Abstract: An apparatus for estimating electrical properties of an electrolyzer includes a data processing system for estimating electrical values, for example a membrane resistance, of the electrolyzer based on a difference voltage, a current, and an initial value and an attenuation time constant of a double-layer capacitance voltage of the electrolyzer during a shutdown of the electrolyzer. The difference voltage is a difference between a voltage of the electrolyzer and a total reversible voltage of the electrolyzer. The initial value and the attenuation time constant of the double-layer capacitance voltage are estimated based on values of the difference voltage when the current is zero and thus the difference voltage equals the double-layer capacitance voltage. The electrical values can be estimated even if a stepwise interruption of the current of the electrolyzer is not possible.

Abstract: A system for alkaline water electrolysis includes electrolysis cells, a hydrogen separator tank, a first piping from the electrolysis cells to the hydrogen separator tank, an oxygen separator tank, a second piping from the electrolysis cells to the oxygen separator tank, and a third piping for conducting liquid electrolyte from the hydrogen separator tank and from the oxygen separator tank back to the electrolysis cells. The system includes an ultrasound source for applying ultrasound on the liquid electrolyte contained by the first piping. The ultrasound enhances the separation of dissolved hydrogen gas from the liquid electrolyte contained by the first piping, and thus energy efficiency of the alkaline water electrolysis is improved. Furthermore, a safe control range of the alkaline water electrolysis is broadened because crossover of hydrogen gas to an oxygen side of the system is reduced.

Abstract: A system for an electrochemical process includes an electrochemical reactor, a converter bridge for supplying direct current to electrodes of the electrochemical reactor, and serial inductors connected to alternating voltage terminals of the converter bridge. The converter bridge includes bi-directional controllable switches between the alternating voltage terminals and direct voltage terminals of the converter bridge. Forced commutation of the bi-directional controllable switches enables reduction of current ripple in the direct current supplied to the electrochemical reactor. The forced commutation enables also to control a power factor of an alternating voltage supply of the system.

Abstract: Optical waveguide cores having refractive index profiles that vary angularly about a propagation axis of the core can provide single-mode operation with larger core diameters than conventional waveguides. In one representative embodiment, an optical waveguide comprises a core that extends along a propagation axis and has a refractive index profile that varies angularly about the propagation axis. The optical waveguide can also comprise a cladding disposed about the core and extending along the propagation axis. The refractive index profile of the core can vary angularly along a length of the propagation axis.

Abstract: An optical beam delivery device is formed of optical fibers configured for beam divergence or mode coupling control. An incident optical beam propagates through a first length of fiber, which is coupled to a second length of fiber and has a first refractive index profile (RIP). The first RIP enables, in response to an applied perturbation, modification of the beam characteristics of the incident optical beam to form an adjusted optical beam having modified beam characteristics relative to beam characteristics of the incident optical beam. The second length of fiber is formed with one or more confinement regions defining a second RIP and arranged to confine at least a portion of the adjusted optical beam. The second and first lengths of fiber are tapered in the direction of light beam propagation to control output beam divergence or susceptibility to beam mode coupling in the first length of fiber, respectively.

Abstract: Additive manufacturing systems and methods for fabricating an article are provided. The additive manufacturing system may include a substrate and a layering device configured to fabricate a first layer of the article on the substrate. The layering device may include an optical beam source configured to generate an optical beam and a variable beam characteristics (VBC) fiber operably coupled with the optical beam source and configured to modify one or more beam characteristics, such as a wavelength, of the optical beam.

Abstract: Optical waveguide cores having refractive index profiles that vary angularly about a propagation axis of the core can provide single-mode operation with larger core diameters than conventional waveguides. In one representative embodiment, an optical waveguide comprises a core that extends along a propagation axis and has a refractive index profile that varies angularly about the propagation axis. The optical waveguide can also comprise a cladding disposed about the core and extending along the propagation axis. The refractive index profile of the core can vary angularly along a length of the propagation axis.

Abstract: Optical waveguide cores having refractive index profiles that vary angularly about a propagation axis of the core can provide single-mode operation with larger core diameters than conventional waveguides. In one representative embodiment, an optical waveguide comprises a core that extends along a propagation axis and has a refractive index profile that varies angularly about the propagation axis. The optical waveguide can also comprise a cladding disposed about the core and extending along the propagation axis. The refractive index profile of the core can vary angularly along a length of the propagation axis.

Abstract: Additive manufacturing systems and methods for fabricating an article are provided. The additive manufacturing system may include a substrate and a layering device configured to fabricate a first layer of the article on the substrate. The layering device may include an optical beam source configured to generate an optical beam and a variable beam characteristics (VBC) fiber operably coupled with the optical beam source and configured to modify one or more beam characteristics, such as a wavelength, of the optical beam.

Abstract: An optical beam delivery device, such as an optical fiber, includes: a first length of fiber having a first refractive index profile (RIP) to enable modification of one or more beam characteristics of an optical beam having a first wavelength; and a second length of fiber having at least one wavelength-modifying confinement region and situated to receive the optical beam from the first length of fiber.

Abstract: An optical beam delivery device is formed of optical fibers configured for beam divergence or mode coupling control. An incident optical beam propagates through a first length of fiber, which is coupled to a second length of fiber and has a first refractive index profile (RIP). The first RIP enables, in response to an applied perturbation, modification of the beam characteristics of the incident optical beam to form an adjusted optical beam having modified beam characteristics relative to beam characteristics of the incident optical beam. The second length of fiber is formed with one or more confinement regions defining a second RIP and arranged to confine at least a portion of the adjusted optical beam. The second and first lengths of fiber are tapered in the direction of light beam propagation to control output beam divergence or susceptibility to beam mode coupling in the first length of fiber, respectively.

Abstract: Optical waveguide cores having refractive index profiles that vary angularly about a propagation axis of the core can provide single-mode operation with larger core diameters than conventional waveguides. In one representative embodiment, an optical waveguide comprises a core that extends along a propagation axis and has a refractive index profile that varies angularly about the propagation axis. The optical waveguide can also comprise a cladding disposed about the core and extending along the propagation axis. The refractive index profile of the core can vary angularly along a length of the propagation axis.

Abstract: Tapered core fibers are produced using tapered core rods that can be etched or ground so that a fiber cladding has a constant diameter. The tapered core can be an actively doped core, or a passive core. One or more sleeving tubes can be collapsed onto a tapered core rod and exterior portions of the collapsed sleeving tubes can be ground to provide a constant cladding diameter in a fiber drawn from the preform.

Abstract: Optical waveguide cores having refractive index profiles that vary angularly about a propagation axis of the core can provide single-mode operation with larger core diameters than conventional waveguides. An optical waveguide includes a core that extends along a propagation axis and has a refractive index profile that varies angularly about the propagation axis. The optical waveguide also includes a cladding disposed about the core and extending along the propagation axis. The refractive index profile of the core varies angularly along a length of the propagation axis.

Abstract: Optical waveguide cores having refractive index profiles that vary angularly about a propagation axis of the core can provide single-mode operation with larger core diameters than conventional waveguides. An optical waveguide includes a core that extends along a propagation axis and has a refractive index profile that varies angularly about the propagation axis. The optical waveguide also includes a cladding disposed about the core and extending along the propagation axis. The refractive index profile of the core varies angularly along a length of the propagation axis.

Abstract: Tapered core fibers are produced using tapered core rods that can be etched or ground so that a fiber cladding has a constant diameter. The tapered core can be an actively doped core, or a passive core. One or more sleeving tubes can be collapsed onto a tapered core rod and exterior portions of the collapsed sleeving tubes can be ground to provide a constant cladding diameter in a fiber drawn from the preform.

Abstract: Optical fibers are provided for modal discrimination which include a central core and a cladding disposed about the central core. The central core has a non-circular and non-elliptical cross-section, and it is rotated about a central axis of the optical fiber along the length of the optical fiber at a selected pitch resulting in the capability of a fundamental mode beam output for large core sizes. An optical system includes a seed optical source configured to provide a seed beam and an optical amplifier configured to receive and amplify the seed beam. The optical amplifier also includes an active optical fiber having a large mode area non-circular and non-elliptical core rotated about a central axis of said active optical fiber to provide modal discrimination and fundamental mode output.

Abstract: Fiber amplifiers and oscillators include tapered waveguides such as optical fibers that permit multimode propagation but produce amplification and oscillation in a fundamental mode. The tapered waveguides generally are provided with an active dopant such as a rare earth element that is pumped with an optical pump source such as one or more semiconductor lasers. The active waveguide taper is selected to taper from a single or few mode section to a multimode section, and seed beam in a fundamental mode is provided to a section of the waveguide taper associated with a smaller optical mode, and an amplified beam exits the waveguide taper at a section associated with a larger optical mode.

Abstract: Optical fibers are provided for modal discrimination which include a central core and a cladding disposed about the central core. The central core has a non-circular and non-elliptical cross-section, and it is rotated about a central axis of the optical fiber along the length of the optical fiber at a selected pitch resulting in the capability of a fundamental mode beam output for large core sizes. An optical system includes a seed optical source configured to provide a seed beam and an optical amplifier configured to receive and amplify the seed beam. The optical amplifier also includes an active optical fiber having a large mode area non-circular and non-elliptical core rotated about a central axis of said active optical fiber to provide modal discrimination and fundamental mode output.