In vitro cultured neonatal mouse calvariae release calcium and buffer the medium proton concentration in response to a decrease in the medium pH caused by a reduction in bicarbonate concentration ([HCO3-]), a model of metabolic acidosis, but not to an equivalent decrease in pH caused by an increase in the partial pressure of carbon dioxide (PCO2), a model of respiratory acidosis. We have postulated that the medium is in equilibrium with the carbonated apatite in bone. To determine whether bone carbonate is depleted during models of acidosis, we cultured calvariae in control medium (pH approximately 7.4, PCO2 approximately 43, [HCO3-] approximately 26) or in medium in which the pH was equivalently reduced by either a decrease in [HCO3-] (metabolic acidosis, pH approximately 7.1, [HCO3-] approximately 13) or an increase in PCO2 (respiratory acidosis, pH approximately 7.1, PCO2 approximately 86) and determined net calcium flux (JCa) and bone carbonate content. We found that compared with control, after 3, 24, and 48 h there was a decrease in bone carbonate content during metabolic but not during respiratory acidosis. Compared with control, at 3 h JCa increased with both respiratory and metabolic acidosis; however, at 24 and 48 h JCa increased only with metabolic acidosis. JCa was correlated inversely with percent bone carbonate content in control and metabolic acidosis at all time periods studied (r = -0.809, n = 23, P < 0.001). Thus a model of metabolic acidosis appears to increase JCa from bone, perhaps due to the low [HCO3-] inducing bone carbonate dissolution.(ABSTRACT TRUNCATED AT 250 WORDS)

Metasurfaces are two-dimensional nanoantenna arrays that can control the propagation of light at will. In particular, plasmonic metasurfaces feature ultrathin thicknesses, ease of fabrication, field confinement beyond the diffraction limit, superior nonlinear properties, and ultrafast performances. However, the technological relevance of plasmonic metasurfaces operating in the transmission mode at optical frequencies is questionable due to their limited efficiency. The state-of-the-art efficiency of geometric plasmonic metasurfaces at visible and near-infrared frequencies, for example, is ≤10%. Here, we report a multipole-interference-based transmission-type geometric plasmonic metasurface with a polarization conversion efficiency that reaches 42.3% at 744 nm, over 400% increase over the state of the art. The efficiency is augmented by breaking the scattering symmetry due to simultaneously approaching the generalized Kerker condition for two orthogonal polarizations. In addition, the design of the metasurface proposed in this study introduces an air gap between the antennas and the surrounding media that confines the field within the gap, which mitigates the crosstalk between meta-atoms and minimizes metallic absorption. The proposed metasurface is broadband, versatile, easy to fabricate, and highly tolerant to fabrication errors. We highlight the technological relevance of our plasmonic metasurface by demonstrating a transmission-type beam deflector and hologram with record efficiencies.

Controllable nanofabrication is at the very foundation of nano-science and nano-technology. Today, ultrafast laser writing has been broadly adopted for micro-fabrication because of its ability to make precise and rapid processing of almost all types of materials in an ambient environment. However, direct laser writing is typically unsuitable for high-quality 2D nano-patterning. In this work, we introduce a maskless laser nano-lithographic technique that allows us to create regular 2D periodic nanopatterns on glass. Glass is a particularly challenging material since it does not absorb light readily. Our strategy starts with a glass sample being coated with a thin layer of metal, and then irradiated with a series of pulse bursts at progressively increasing fluence levels. This process allows us to sequentially activate a series of tailored physical processes that lead to the formation of regular 2D periodic nanopatterns on glass. The formation mechanism of this nano-patterning is also simulated numerically and further corroborated by a series of control experiments. We also show controllability in forming various shapes and sizes of nanopatterns through tailored fluence doses. Our technique provides a high-speed and low-cost method for glass nanofabrication.

The ability of an interferometer to characterize the spatial information of a light beam is often limited by the temporal profile of the beam, with femtosecond pulse characterization being particularly challenging. In this study, we developed a simple, stable, controllable shearing and vectorial phase-shifting wedged reversal shearing interferometer that is able to characterize all types of coherent and partially coherent light beams. The proposed interferometer consists of only a single beam splitter cube with one wedged entrance face and is insensitive to environmental vibration due to its common path configuration. A near zero-path length difference of the proposed interferometer ensures its operation for ultrashort pulses, providing, for the first time, a simple and stable interferometric tool to fully characterize sub-100  fs laser pulses. All common beam characterization can be carried out with the interferometer, such as the amplitude, phase, polarization, wavelength, and pulse duration. Furthermore, this technique is sensitive to the wavefront tilt and can be used for precise beam alignment. Therefore, this interferometer can be an essential tool for beam characterization, optical imaging, and the testing required for a wide range of applications, including astronomy, biomedicine, ophthalmology, optical testing and imaging systems, and adaptive optics.

Femtosecond laser-induced herringbone patterns are formed on copper (Cu). These novel periodic structures are created following s-polarized, large incident angle, femtosecond laser pulses. Forming as slanted and axially symmetric laser-induced periodic surface structures along the side walls of ablated channels, the result is a series of v-shaped structures that resemble a herringbone pattern. Fluence mapping, incident angle studies, as well as polarization studies have been conducted and provide a clear understanding of this new structure.

Femtosecond-laser surface structuring on metals is investigated in real time by both fundamental and second harmonic generation (SHG) signals. The onset of surface modification and its progress can be monitored by both the fundamental and SHG probes. However, the dynamics of femtosecond-laser-induced periodic surface structures (FLIPSSs) formation can only be revealed by SHG but not fundamental because of the higher sensitivity of SHG to structural geometry on metal. Our technique provides a simple and effective way to monitor the surface modification and FLIPSS formation thresholds and allows us to obtain the optimal FLIPSS for SHG enhancement.

In this study, we develop a simple but highly effective technique that generates a continuously varying polarization within a laser beam. This is achieved by having orthogonal linear polarizations on each side of the beam. By simply focusing such a laser beam, we can attain a gradually and continuously changing polarization within the entire Rayleigh range due to diffraction. To demonstrate this polarization distribution, we apply this laser beam onto a metal surface and create a continuously rotating laser induced periodic surface structure pattern. This technique provides a very effective way to produce complex surface structures that may potentially find applications, such as polarization modulators and metasurfaces.

In this study, we demonstrate a compact vectorial optical field generator for any coherent light, including femtosecond laser beams. The apparatus utilizes a single Köster prism for both beam splitting and recombining. A phase-only spatial light modulator is used as a diffractive optical element to encode the two complex fields that recombine after being converted to orthogonal polarizations, generating an arbitrary vectorial optical field. We apply this setup to shape focused femtosecond pulses in producing patterned structures.