Single-beam optical trapping of micrometer-sized dielectric particles is experimentally demonstrated using radially and azimuthally polarized beams. The axial and transverse optical trapping ...efficiencies of glass and polystyrene beads suspended in water are measured. The radially polarized beam exhibited the highest trapping efficiency in the axial direction due to the p polarization of the radial polarization on the particle surface. On the other hand, the azimuthally polarized beam had a higher transverse trapping efficiency than the radially polarized beam. These results are consistent with numerical predictions.
Autologous split-thickness skin grafts are the preferred treatment for excised burn wounds, but donor sites for autografting are often limited in patients with extensive burns. A number of ...alternative treatments are already in use to treat large burns and ulcers. Despite intense efforts to develop tissue-engineered skin, delayed or absent vascularization is one of the major reasons for tissue-engineered skin engraftment failure. To overcome these problems, we developed a scaffold-free 3-dimensional (3D) skin substitute containing vascular networks that combine dermal fibroblasts, endothelial cells, and epidermal keratinocytes based on our layer-by-layer cell coating technique. We transplanted the pre-vascularized 3D skin substitutes onto full-thickness skin defects on severe combined immunodeficiency mice to assess their integration with the host tissue and effects on wound healing. We used non-vascularized 3D skin substitutes as a control. Vessels containing red blood cells were evident in the non-vascularized control by day 14. However, blood perfusion of the human-derived vasculature could be detected within 7 days of grafting. Moreover, the pre-vascularized 3D skin substitutes had high graft survival and their epidermal layers were progressively replaced by mouse epidermis. We propose that a novel dermo-epidermal 3D skin substitute containing blood vessels can promote efficient reconstruction of full-thickness skin defects.
The spatial resolution characteristics in confocal laser scanning microscopy (LSM) and two-photon LSM utilizing a higher-order radially polarized Laguerre-Gaussian (RP-LG) beam are numerically ...analyzed. The size of the point spread function (PSF) and its dependence on the confocal pinhole size are compared with practical LSM using a circularly polarized Gaussian beam on the basis of vector diffraction theory. The spatial frequency response in terms of the optical transfer function (OTF) is also evaluated for LSM using the RP-LG beam. The smaller focal spot characteristics of higher-order RP-LG beams contribute to a dramatic enhancement of the lateral spatial resolution in confocal LSM and two-photon LSM.
In this paper, all molecules (1,2-ethanediol, ethanol, methoxymethanol, dimethyl ether, and dimethyl peroxide) predicted to be produced as a result of C–C, C–O, or O–O bond formation between methanol ...molecules induced by laser-driven shock wave were detected and identified by gas chromatography-mass spectroscopy. In this process, the ultrahigh pressure resulting from the shock wave is considered to reduce the interatomic distance between molecules to mechanically create a new chemical bond. Methoxymethanol production was further verified by infrared absorption spectroscopy of the laser-irradiated methanol concentrated by vacuum distillation. In the concentrated sample, polyoxymethylene hemiformals, which are presumably produced by the polymerization of methoxymethanol, were also found.
Mechanically induced C−C bond formation was demonstrated by the laser driven shock wave generated in liquid normal alkanes at room temperature. Gas chromatography mass spectrometry analysis revealed ...the dehydrogenation condensation between two alkane molecules, for seven normal alkanes from pentane to undecane. Major products were identified to be linear and branched alkane molecules with double the number of carbons, and exactly coincided with the molecules predicted by supposing that a C−C bond was formed between two starting molecules. The production of the alkane molecules showed that the C−C bond formation occurred almost evenly at all the carbon positions. The dependence of the production on the laser pulse energy clearly indicated that the process was attributed to the shock wave. The C−C bond formation observed was not a conventional passive chemical reaction but an unprecedented active reaction.
Double up: A mechanically induced chemical reaction was demonstrated by laser‐driven shock wave pressure in a liquid. Reduction of the molecular distance between alkane molecules by the laser shock wave gave rise to the formation of a C−C bond, creating an alkane molecule with double the number of carbon atoms. All combinations between carbon atoms for each alkane molecule were verified.
We present a systematic study of the superposition of two vector Laguerre-Gaussian (LG) beams. Propagation depended field distribution obtained from the superposition of two vector LG beams has many ...interesting features of intensity and polarization. Characteristic inhomogeneous polarization distribution of the vector LG beam appears in the form of azimuthally modulated intensity and polarization distributions in the superposition of the beams. We found that the array of polarization singular points, whose number depends upon the azimuthal indices of the two beams, evolves during propagation of the field. The position and number of C-points generated in the field were analyzed using Stokes singularity relations. Novel intensity and polarization patterns obtained from the superposition of two vector LG beams may find applications in the field of molecular imaging, optical manipulation, atom optics, and optical lattices.
In this study, femtosecond laser-based multi-beam interference laser processing on nanofilms with nanometer thicknesses was demonstrated. The resulting multi-hole, two-dimensional lattice pattern ...reflected a laser interference fringe formed on the surface of the nanofilm, with no breaks or cracks. In anticipation of the actual nanostructure fabrication, additional laser processing was performed to drill additional holes in the spaces between the existing holes, resulting in high-density multi-point hole drilling beyond the interference fringe pitch. Notably, processing materials with thicknesses close to 100 nm or less is difficult even with a state-of-the-art focused-ion-beam system. The presented method, in contrast, allows instantaneous, submicrometer-scale multi-point hole drilling of nanofilms over a large area, opening up a new frontier of nanoengineering. Future applications will include the fabrication of electron phase plates, membrane-based optomechanical devices, microelectromechanical systems, and engineering of atomic layer materials.
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