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Optical properties of spherical gold particles with diameters of 150-650 nm (mesoparticles) are studied by reflectance spectroscopy. Particles are fabricated by laser-induced transfer of metallic droplets onto metal and dielectric substrates. Contributions of higher multipoles (beyond the quadrupole) in the scattering spectra of individual spherical particles are experimentally observed. These observations are performed for particles in a homogeneous environment and for particles located in air on a metal surface. Good agreement between calculations on the basis of Mie theory and experimental results obtained in homogeneous environment is demonstrated. Multipole resonance features in the experimental reflection spectra of particles located on a gold substrate, in the wavelength range of 500-1000 nm, are discussed and theoretically analyzed on the basis of finite-difference time-domain simulations. High-resolution Raman images of mesoparticle pairs at different polarizations of light are also presented. [ABSTRACT FROM AUTHOR]

In this work, we have synthesized and characterized a novel, titanium-containing hybrid material that can be structured three-dimensionally using two-photon polymerization. We investigate the effect on the structurability of the increase of titanium isopropoxide and methacrylic acid in this photosensitive composite. We show that while it is possible to make transparent thin films with a titanium isopropoxide molar content as high as 90%, three-dimensional structures can be made only when the titanium isopropoxide molar content is less than 50%. We measure the refractive index of films with different titanium isopropoxide: methacrylic acid concentrations and we show that while the refractive index increases linearly with the titanium isopropoxide, the increase of the methacrylic acid content does not affect the refractive index of the material. [ABSTRACT FROM AUTHOR]

Isotopically enriched 10boron for use in pillar-structured neutron detectors was successfully etched in an electron cyclotron resonance (ECR) plasma using SF6-based plasmas. The effects of radio frequency (RF) power, ECR power, gas flow rate, H2 and O2 incorporation into the plasma, and gas mixture ratios were examined. Etch rates up to approximately 1.35 μm/min were realized. In addition, etch morphology was examined, and the final shape of 10boron-coated pillars could be controlled through the etch gas mixture utilized. Selectivity to the underlying Si structure was apparent from scanning electron microscopy (SEM) micrographs of completed etches. [ABSTRACT FROM AUTHOR]

Renewed and growing interest in the field of surface plasmon polaritons (SPPs) comes from a rapid advance of nanostructuring technologies. In this paper, we will report on the application of two-photon polymerization (2PP) technique for the fabrication of dielectric SPP-structures, which can be used for localization, guiding, and manipulation of SPPs on a subwavelength scale. This technology is based on nonlinear absorption of near-infrared femtosecond laser pulses. Resolutions down to 100 nm (and even better) are already achievable. Characterization of these structures is performed by leakage radiation microscopy. 2PP allows the fabrication of dielectric waveguides, splitters, and couplers directly on metal surfaces. The dielectric structures on metal films are demonstrated to be very efficient for the excitation of SPPs. Using these structures, one can achieve excitation and focusing of the resulting plasmon field. [ABSTRACT FROM AUTHOR]

This work demonstrates the fast generation and rapid replication of laser-fabricated three-dimensional conical microstructures on single-crystalline silicon. Large areas containing Si structures are fabricated by fast scanning of the focussed laser beam of a high-power, high repetition rate infrared picosecond laser system over the Si surface, in the presence of SF6. Furthermore, the possibility of replicating the initial spiked morphology on other materials is demonstrated by polydimethylsiloxane molding in vacuum. Results showing the successful transfer of the initial conical morphology on the photocurable resist material ORMOCER (an organically modified ceramic) are presented. The combination of laser-based methods and standard replication technology may open up interesting prospects for the fast and efficient transfer of three-dimensional patterns over a wide range of materials. [ABSTRACT FROM AUTHOR]

To overcome limitations in the high harmonic conversion efficiency, the possibility of parametric amplification in the VUV and XUV is considered. Potential approaches, including parametric gain transfer from low- to high-order processes, are discussed. Experimentally, a near two photon resonant parametric gain scheme in xenon, excited by femtosecond KrF laser radiation at ωp = 248 nm, was investigated, leading to signal (ωs) and idler (ωi) emissions at 149 nm and 760 nm according to 2ωp = ωs + ωi. For the signal field at 149 nm an exponential increase with density and length is obtained. By tuning the excimer laser radiation slightly towards the two-photon resonance, a macroscopic amplification of about 50 at 149 nm was measured. In addition, a sum-mixing signal at 106 nm according to ωsum = 2ωp + ωi, showing a similar exponential increase as the 149-nm signal, is observed, which indicates a coupling of both processes with a gain transfer by the common idler field. [ABSTRACT FROM AUTHOR]

For the efficient frequency tripling of KrF laser radiation, argon is very well suited as a nonlinear medium since a near-three-photon resonance can be used, which enhances the nonlinear susceptibility. According to theoretical predictions a zero crossing of the dispersive phase mismatch for the frequency-tripling process allows nearly perfect phase matching at high densities for the central KrF laser wavelength at 248.5 nm. Experiments that demonstrate the associated spectral sensitivity of the phase matching were performed in a pulsed argon gas jet for controlled input spectra and by varying the particle density up to 6 × 10[SUP18] cm[SUP-3]. The experiments show good agreement with corresponding theoretical model calculations and explain the recently achieved high conversion efficiencies in frequency tripling of short-pulse KrF laser radiation. [ABSTRACT FROM AUTHOR]

Investigations of the efficient generation of powerful coherent radiation at 82.8 nm by frequency tripling of short-pulse KrF laser radiation are presented. Argon gas is selected as nonlinear medium due to the resonantly enhanced 3rd-order susceptibility Χ[sup (3)](-3ω, ω, ω, ω). Pulse energies of 100 µJ at 82.8 nm have been measured for a pump pulse energy of 14 mJ. An upscaling to more than 500 µJ is expected with available more powerful pump lasers. Features of this XUV source and possible applications are discussed. [ABSTRACT FROM AUTHOR]

Immature ovaries of Drosophila mercatorum were injected into young larvae and into adult males of D. mercatorum, D. melanogaster, D. hydei, D. virilis, and Zaprionius vittiger. These homo- and heteroplastic transplantations allow normal vitellogenesis to occur in the donor ovary. By SDS gel electrophoresis, we identified the major species-specific yolk proteins of mature eggs (stage 14) which were exclusively of donor-specific origin. Other experiments with D. hydei and Z. vittiger showed that, when females were used as hosts, the host-specific yolk proteins became incorporated into the donor eggs. When two immature ovaries, one of D. mercatorum and one of D. hydei, were co-cultured in males, again only the donor-specific yolk proteins were found in the mature eggs implying that these yolk proteins were not released into the host hemolymph. A parthenogenetic strain of D. mercatorum was used to demonstrate the ability of transplanted immature ovaries to produce viable eggs which can give rise to fertile adults. The role of the species-specific yolk proteins is discussed with respect to the dual origin of these proteins during normal vitellogenesis, i.e., an autonomous synthesis within the ovary itself in addition to the well-known production by the fat body. Further experiments with pupae as hosts indicate that even in the absence of juvenile hormone and in the presence of high doses of ecdysone, vitellogenesis can proceed within the donor ovary. Based on these experiments, a new hyopthesis on the hormonal control of vitellogenesis in Drosophila is presented. We propose that yolk proteins derived from the fat body are controlled by juvenile hormone, whereas the independent and autonomous vitellogenesis within the ovary itself is controlled by endogenously synthesized ecdysone. [ABSTRACT FROM AUTHOR]

The gut microbiota influences intestinal barrier integrity through mechanisms that are incompletely understood. Here we show that the commensal microbiota weakens the intestinal barrier by suppressing epithelial neuropilin-1 (NRP1) and Hedgehog (Hh) signaling. Microbial colonization of germ-free mice dampens signaling of the intestinal Hh pathway through epithelial Toll-like receptor (TLR)-2, resulting in decreased epithelial NRP1 protein levels. Following activation via TLR2/TLR6, epithelial NRP1, a positive-feedback regulator of Hh signaling, is lysosomally degraded. Conversely, elevated epithelial NRP1 levels in germ-free mice are associated with a strengthened gut barrier. Functionally, intestinal epithelial cell-specific Nrp1 deficiency (Nrp1 ΔIEC ) results in decreased Hh pathway activity and a weakened gut barrier. In addition, Nrp1 ΔIEC mice have a reduced density of capillary networks in their small intestinal villus structures. Collectively, our results reveal a role for the commensal microbiota and epithelial NRP1 signaling in the regulation of intestinal barrier function through postnatal control of Hh signaling., (© 2023. The Author(s).)