Reconfigurable scan lens based on an actively controlled optical phased array.

Integrated photonics provides a path for miniaturization of an optical system to a compact chip scale and offers reconfigurability by the integration of active components. Here we report a chip-scale reconfigurable scan lens based on an optical phased array, consisting of 30 actively controlled elements on the InP integrated photonic platform. By configuring the phase shifters, we show scanning of a nearly diffraction-limited focused spot with a full width at half maximum spot size down to 2.

Increasing responsivity-bandwidth margin of germanium waveguide photodetector with simple corner reflector.

The external bandwidth of germanium waveguide photodetectors (PDs) decreases with the device length due to the load and parasitic effects even if the internal one is less affected. Shortening PDs raises the external bandwidth but lowers the responsivity, introducing a trade-off between the two figures of merits. Here, we present a scheme of waveguide PDs based on total internal reflections of corner reflectors.

A NaI(Tl)-based radioactive noble-gas monitoring system used for radiation monitoring.

Radioactive noble-gas monitoring is necessary in nuclear facilities. A NaI(Tl)-based radioactive noble-gas monitoring system was developed. In order to increase the amount of air to be measured, the sample vessel of this system was larger than that of other systems, and was pressurized to about 5 × 10 Pa.

High-speed integrated micro-LED array for visible light communication.

In this Letter, we report high-speed integrated 14 µm in diameter micro-light-emitting diode (μLED) arrays with the parallel configuration, including ${2} \times {2}$2×2, ${2} \times {3}$2×3, ${2} \times {4}$2×4, and ${2} \times {5}$2×5 arrays. The small junction area of μLED (${\sim}{191}\;\unicode{x00B5}{\rm m}^2$∼191µm) in each element facilitates the operation of higher injection current density up to ${13}\;{{\rm kA/cm}^2}$13kA/cm, leading to the highest modulation bandwidth of 615 MHz. The optical power of ${2} \times {5}$2×5 array monotonically increases (${\sim}{10}$∼10 times higher) as the number of arrays increases (1 to 10), while retaining the fast modulation bandwidth.

Radon removal trap design and coefficient testing for the development of an effective radioxenon sampling, separation and measurement system.

To monitor low-level radioxenon isotopes activity concentrations in the bulk gases, a radioxenon sampling, separation and measurement system has been developed. The xenon enrichment factor of this system is more than 10 after the separation of impurities, including N, O, COand HO, as well as radon and its progenies, such as Pb and Bi. Since radon and its progenies interfere with radioxenon measurement, they have to be removed before radioxenon counting.

Red/green/blue LD mixed white-light communication at 6500K with divergent diffuser optimization.

Enabling laser white-lighting at a correlated color temperature (CCT) of 6500K with the use of only red/green/blue (RGB) tri-color laser diodes (LDs) is demonstrated, which can further perform wavelength division multiplexing (WDM) communication with a high-spectral-usage 16 QAM-OFDM data stream at 11.2 Gbps over 0.5 m.

Escherichia coli Fiber Sensors Using Concentrated Dielectrophoretic Force with Optical Defocusing Method.

A sensitive tapered optical fiber tip combined with dielectrophoretic (DEP) trapping was used for rapid and label-free detection of bacteria in water. The angular spectrum of the optical field at the fiber tip was changed with the surrounding refractive index (RI). By measuring far-field intensity change at the defocus plane, the intensity sensitivity was up to 95 200%/RIU (RI unit), and the detection limit was 5.

Blue Laser Diode Based Free-space Optical Data Transmission elevated to 18 Gbps over 16 m.

Up to 18-Gbps direct encoding of blue laser diode (BLD) is demonstrated for free-space data transmission. By reshaping the orthogonal frequency multiplexed (16-QAM OFDM) stream with sidelobe filtering, the raw data rate expedites from 17.2 to 18.

Broadband optical waveguide couplers with arbitrary coupling ratios designed using a genetic algorithm.

In this work, we present a generalized design of broadband optical waveguide couplers with arbitrary coupling ratios on the silicon-on-insulator platform. The device is segmented into 34 short sections, where the propagation constant and the coupling coefficient of each section are viewed as variables during the optimization process. The optimal variable combination is determined by a genetic algorithm.

Development of a mobile radioxenon processing system for on-site inspections and the deployment in IFE14.

A mobile radioxenon gas processing system (XESPM-III) was developed for on-site inspections-targeting deployment in the Integrated Field Exercise in Jordan 2014 (IFE14)-in order to monitor radioxenon isotopes (Xe) from the subsoil and atmosphere. XESPM-III is composed of primarily three units, the sampling unit, the purification unit and finally the quantification unit. The function of the sampling unit is to pre-enrich xenon by removal of impurities in the gas sample, while the purification unit further purifies, separates impurities and prepares a small-volume sample with relatively high concentration of xenon gas-both stable and radioactive xenon (if present).

Sensitive Detection of Small Particles in Fluids Using Optical Fiber Tip with Dielectrophoresis.

This work presents using a tapered fiber tip coated with thin metallic film to detect small particles in water with high sensitivity. When an AC voltage applied to the Ti/Al coated fiber tip and indium tin oxide (ITO) substrate, a gradient electric field at the fiber tip induced attractive/repulsive force to suspended small particles due to the frequency-dependent dielectrophoresis (DEP) effect. Such DEP force greatly enhanced the concentration of the small particles near the tip.

Multi-level surface enhanced Raman scattering using AgOx thin film.

Ag nanostructures with surface-enhanced Raman scattering (SERS) activities have been fabricated by applying laser-direct writing (LDW) technique on silver oxide (AgOx) thin films. By controlling the laser powers, multi-level Raman imaging of organic molecules adsorbed on the nanostructures has been observed. This phenomenon is further investigated by atomic-force microscopy and electromagnetic calculation.

Plasmonic ZnO/Ag embedded structures as collecting layers for photogenerating electrons in solar hydrogen generation photoelectrodes.

A new fabrication strategy in which Ag plasmonics are embedded in the interface between ZnO nanorods and a conducting substrate is experimentally demonstrated using a femtosecond-laser (fs-laser)-induced plasmonic ZnO/Ag photoelectrodes. This fs-laser fabrication technique can be applied to generate patternable plasmonic nanostructures for improving their effectiveness in hydrogen generation. Plasmonic ZnO/Ag nanostructure photoelectrodes show an increase in the photocurrent of a ZnO nanorod photoelectrodes by higher than 85% at 0.

Fabrication of three-dimensional plasmonic cavity by femtosecond laser-induced forward transfer.

We fabricated a three-dimensional five-layered plasmonic resonant cavity by low-cost, efficient and high-throughput femtosecond laser-induced forward transfer (fs-LIFT) technique. The fabricated cavity was characterized by optical measurements, showing two different cavity modes within the measured wavelength region which is in good agreement with numerical simulations. The mode volume corresponding to each resonance is found to be squeezed over 10(4) smaller than the cube of incident wavelength.

Fabrication of plasmonic devices using femtosecond laser-induced forward transfer technique.

Using femtosecond laser-induced forward transfer techniques we have fabricated gold dots and nanoparticles on glass substrates, as well as nanobumps on gold thin film. The surface morphologies of these structures with different laser fluences and film thicknesses are investigated. We also study the focusing and defocusing properties of the nanofence-an arranged nanobump pattern-by the total-internal reflection microscope.

Fast fabrication of a Ag nanostructure substrate using the femtosecond laser for broad-band and tunable plasmonic enhancement.

Using a femtosecond laser, we have transformed the laser-direct-writing technique into a highly efficient method that can process AgO(x) thin films into Ag nanostructures at a fast scanning rate of 2000 μm(2)/min. The processed AgO(x) thin films exhibit broad-band enhancement of optical absorption and effectively function as active SERS substrates. Probing of the plasmonic hotspots with dyed polymer beads indicates that these hotspots are uniformly distributed over the treated area.

Improve efficiency of white organic light-emitting diodes by using nanosphere arrays in color conversion layers.

The authors demonstrated an efficient color conversion layer (CCL) by using nanosphere arrays in down-converted white organic light-emitting diodes (WOLEDs). The introduced periodical nanospheres not only helped extract the confined light in devices, but also increased the effective light path to achieve high-efficiency color conversion. By applying a CCL with red phosphor on a 400-nm-period nanosphere array, we achieved 137% color conversion ratio for blue OLEDs, which was 2.

Nanofluidic refractive-index sensors formed by nanocavity resonators in metals without plasmons.

Nanocavity resonators in metals acting as nanofluidic refractive-index sensors were analyzed theoretically. With the illumination of transverse electric polarized light, the proposed refractive index sensor structure acts as a pure electromagnetic resonator without the excitation of surface plasmons. The reflected signal from the nanocavity resonators can be very sensitive to the refractive index of the fluids inside the nanocavities due to the enhancement of the electric field of the resonant mode inside the cavities.