Laser-Induced, Polarization Dependent Shape Transformation of Au/Ag Nanoparticles in Glass

Bimetallic, initially spherical Ag/Au nanoparticles in glass prepared by ion implantation have been irradiated with intense femtosecond laser pulses at intensities still below the damage threshold of the material surface. This high-intensity laser processing produces dichroism in the irradiated region, which can be assigned to the observed anisotropic nanoparticle shapes with preferential orientation of the longer particle axis along the direction of laser polarization. In addition, the particle sizes have considerably been increased upon processing

Multicore fibers with 10 and 16 single-mode cores for the visible spectrum

We report multicore fibers (MCFs) with 10 and 16 linearly distributed cores with single-mode operation in the visible spectrum. The average propagation loss of the cores is 0.06 dB/m at λ = 445 nm and < 0.03 dB/m at wavelengths longer than 488 nm. The low inter-core crosstalk and nearly identical performance of the cores make these MCFs suitable for spatial division multiplexing in the visible spectrum. As a proof-of-concept application, one of the MCFs was coupled to an implantable neural probe to spatially address light-emitting gratings on the probe

Low-loss broadband bi-layer edge couplers for visible light

Low-loss broadband fiber-to-chip coupling is currently challenging for visible-light photonic-integrated circuits (PICs) that need both high confinement waveguides for high-density integration and a minimum feature size above foundry lithographical limit. Here, we demonstrate bi-layer silicon nitride (SiN) edge couplers that have ≤ 4 dB/facet coupling loss with the Nufern S405-XP fiber over a broad optical wavelength range from 445 to 640 nm. The design uses a thin layer of SiN to expand the mode at the facet and adiabatically transfers the input light into a high-confinement single-mode waveguide (150-nm thick) for routing, while keeping the minimum nominal lithographic feature size at 150 nm. The achieved fiber-to-chip coupling loss is about 3 to 5 dB lower than that of single-layer designs with the same waveguide confinement and minimum feature size limitation

Power-efficient silicon nitride thermo-optic phase shifters for visible light

We demonstrate power-efficient, thermo-optic, silicon nitride waveguide phase shifters for blue, green, and yellow wavelengths. The phase shifters operated with low power consumption due to a suspended structure and multi-pass waveguide design. The devices were fabricated on 200-mm silicon wafers using deep ultraviolet lithography as part of an active visible-light integrated photonics platform. The measured power consumption to achieve a π phase shift (averaged over multiple devices) was 0.78, 0.93, 1.09, and 1.20 mW at wavelengths of 445, 488, 532, and 561 nm, respectively. The phase shifters were integrated into Mach-Zehnder interferometer switches, and 10 − 90% rise(fall) times of about 570(590) μs were measured

Controlled modification of optical and structural properties of glass with embedded silver nanoparticles by nanosecond pulsed laser irradiation

Glass with embedded spherical silver nanoparticles of ~15 nm in radius contained in a layer with thickness of ~20 µm was irradiated using a nanosecond (36 ns) pulsed laser at 532 nm. Laser irradiation led to the formation of a thin surface film containing uniformly distributed nanoparticles - with an increase in the overall average nanoparticle size. Increasing the applied number of pulses to the sample resulted in the increase of the average size of the nanoparticles from 15 nm to 35 – 70 nm in radius, and narrowing of the surface plasmon band compared to the absorption spectra of the original glass sample. The influence of the applied number of laser pulses on the optical and structural properties of such a recipient nanocomposite was investigated

Implantable Photonic Neural Probes with 3D-Printed Microfluidics and Applications to Uncaging

Advances in chip-scale photonic-electronic integration are enabling a new generation of foundry-manufacturable implantable silicon neural probes incorporating nanophotonic waveguides and microelectrodes for optogenetic stimulation and electrophysiological recording in neuroscience research. Further extending neural probe functionalities with integrated microfluidics is a direct approach to achieve neurochemical injection and sampling capabilities. In this work, we use two-photon polymerization 3D printing to integrate microfluidic channels onto photonic neural probes, which include silicon nitride nanophotonic waveguides and grating emitters. The customizability of 3D printing enables a unique geometry of microfluidics that conforms to the shape of each neural probe, enabling integration of microfluidics with a variety of existing neural probes while avoiding the complexities of monolithic microfluidics integration. We demonstrate the photonic and fluidic functionalities of the neural probes via fluorescein injection in agarose gel and photoloysis of caged fluorescein in solution and in flxed brain tissue

Microcantilever-integrated photonic circuits for broadband laser beam scanning

Laser beam scanning is central to many applications, including displays, microscopy, three-dimensional mapping, and quantum information. Reducing the scanners to microchip form factors has spurred the development of very-large-scale photonic integrated circuits of optical phased arrays and focal plane switched arrays. An outstanding challenge remains to simultaneously achieve a compact footprint, broad wavelength operation, and low power consumption. Here, we introduce a laser beam scanner that meets these requirements. Using microcantilevers embedded with silicon nitride nanophotonic circuitry, we demonstrate broadband, one- and two-dimensional steering of light with wavelengths from 410 nm to 700 nm. The microcantilevers have ultracompact ~0.1 mm$^2$ areas, consume ~31 to 46 mW of power, are simple to control, and emit a single light beam. The microcantilevers are monolithically integrated in an active photonic platform on 200-mm silicon wafers. The microcantilever-integrated photonic circuits miniaturize and simplify light projectors to enable versatile, power-efficient, and broadband laser scanner microchips

Modification of coating-substrate systems under the action of compression plasma flow

The results of studying changes in physical and mechanical properties of coating-substrate systems subjected to the compression plasma flow are presented. The possibility for doping the substrate both with pre-deposited coating components and with plasma-forming substance during liquid-phase mixing and resolidification of near-surface layers melted by the compression plasma flow is shown.Представлено результати досліджень зміни фізико-механічних властивостей систем покриття-підкладка при впливі на них компресійним плазмовим потоком. Продемонстровано можливість легування матеріалу підкладки як компонентом попередньо нанесеного покриття, так і робочою речовиною плазми, у процесі рідкофазного перемішування і перезатвердіння розплавлених під дією компресійного плазмового потоку приповерхніх шарів.Представлены результаты исследований изменения физико-механических свойств систем покрытие- подложка при воздействии на них компрессионным плазменным потоком. Продемонстрирована возможность легирования материала подложки как компонентом предварительно нанесенного покрытия, так и рабочим веществом плазмы, в процессе жидкофазного перемешивания и перезатвердевания расплавленных под действием компрессионного плазменного потока приповерхностных слоев