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Narrowband and high-transmission optical filters are extensively used in color display technology, optical information processing, and high-sensitive sensing. Because of large ohmic losses in metallic nanostructures, metallic filters usually exhibit low transmittances and broad bandwidths. By employing both strong field enhancements in metallic nano-slits and the Wood's anomaly in a periodic metallic grating, an extra-narrowband and high-transmission metallic filter is numerically predicted in an ultrathin single-layer metallic grating. Simulation results show that the Wood's anomaly in the ultrathin (thickness H = 60 nm) single-layer metallic grating results in large field enhancements in the substrate and low losses in the metallic grating. As a result, the transmission bandwidth (transmittance T > 60%) at λ = 1200 nm is as small as ΔλFWHM = 1.6 nm, which is smaller than 4% of that in the previous thin dielectric and metallic filters. The corresponding quality factor is as high as Q = λ/ΔλFWHM = 750, which is 40 times greater than that in the previous reports. Moreover, the thickness of our metallic filter (H = 60 nm) is smaller than 40% of that in the previous reports, and its maximum transmittance can reach up to 80%. In experiments, a narrowband metallic filter with a bandwidth of about ΔλFWHM = 10 nm, which is smaller than 25% of that in the previous metallic filters, is demonstrated. [ABSTRACT FROM AUTHOR]

Dynamic topological photonics is a novel research field, combining the time-domain optics and topological physics. In this review, the recent progress and realization platforms of dynamic topological photonics have been well introduced. The definition, measurement methods and the evolution process of the dynamic topological photonics are demonstrated to better understand the physical diagram. This review is meant to bring the readers a different perspective on topological photonics, grasp the advanced progress of dynamic topology, and inspire ideas about future prospects. [ABSTRACT FROM AUTHOR]

Topological materials have great potential in lossless electronic transportation. Bi2Te3 as three‐dimensional (3D) topological insulator is predicted to exhibit many amazing electromagnetic characteristics, which are widely studied all over the world. However, current research available on Bi2Te3 materials is not adequate, and a comprehensive understanding of its properties is necessary. In this work, near‐field plasmon imaging based on Bi2Te3 nanostructures and the kinetic energy spectra of emitted electrons from Bi2Te3 film by using photoemission electron microscope instruments is studied. Under UV laser excitation of 273 nm, the electrons can be excited from the trap states in bandgap, which provides a feasible idea for observing the trap energy levels of Bi2Te3 materials. Moreover, the imaging applications of nanostructures in Bi2Te3 film based on their polarization‐dependence and wavelength‐dependence properties are also demonstrated, providing a more degrees of freedom for imaging, and can realize multidimensional and multi‐multiplexing imaging technology of topological materials. This work provides a novel method to enrich the Bi2Te3 film properties from the view of near‐field plasmon imaging and kinetic energy distribution, paving the way for realizing practical applications of topological materials. [ABSTRACT FROM AUTHOR]

Through theoretical analysis, we show how aligning pulse durations affect the degree and the time-rate slope of nitrogen field-free alignment at a fixed pulse intensity. It is found that both the degree and the slope first increase, then saturate, and finally decrease with the increasing pump duration. The optimal durations for the maximum degree and the maximum slope of the alignment are found to be different. Additionally, they are found to mainly depend on the molecular rotational period, and are affected by the temperature and the aligning pump intensities. The mechanism of molecular alignment is also discussed. [ABSTRACT FROM AUTHOR]

Nanorods are building blocks of three-dimensional photonic crystals and other nanostructures fabricated by multi-photon polymerization with femtosecond laser pulses. The aspect ratios of their cross sections are critical to the in-plane and the interlayer rod distances, which greatly affect the performance. Here we demonstrate the control of aspect ratios from ∼3 to 0.85. At a high scanning speed, aspect ratios can be smaller than unity with a lateral size of ∼150 nm. The results indicate that cylindrical nanorods can be polymerized by the commonly used transverse scanning method to improve the qualities of three-dimensional nanostructures. [ABSTRACT FROM AUTHOR]

We propose and implement a wide-field vibrational phase contrast detection to obtain imaging of imaginary components of third-order nonlinear susceptibility in a coherent anti-Stokes Raman scattering (CARS) microscope with full suppression of the non-resonant background. This technique is based on the unique ability of recovering the phase of the generated CARS signal based on holographic recording. By capturing the phase distributions of the generated CARS field from the sample and from the environment under resonant illumination, we demonstrate the retrieval of imaginary components in the CARS microscope and achieve background free coherent Raman imaging. [ABSTRACT FROM AUTHOR]

We perform a kinetically complete measurement on the fragmentation of Coulomb explosion of H2O molecules in intense few-cycle linearly and circularly polarized laser fields. Both the fragmentations of H2O3+ and H2O4+ reveal the concerted pathway of dissociation. The length of the O—H bond prior to the Coulomb explosion of both molecular ions is sensitive to the laser pulse duration and laser intensity. However, the bending angle of H—O—H is less sensitive to the pulse duration and laser intensity. We introduce the mechanism of charge resonance enhanced double ionization to elucidate the triple (or quadruple) dissociative ionization dynamics of H2O, in which two electrons are non-adiabatically localized at the protons of the precursor ion H2O+ (or H2O2+) and are released simultaneously due to the over barrier ionization in the combined laser field and molecular ionic potential. Such charge resonance enhanced multiple ionization is not suppressed in few-cycle laser fields and elliptically polarized laser fields. [ABSTRACT FROM AUTHOR]

Tryptophan (Trp) is an intrinsic fluorescent probe for detecting the site-specified dynamics inside/outside protein. It is found that the Trp can easily be inserted in desired sites of protein, which affects the integrity of the overall structure. To evaluate this effect, we design thirteen double point mutants of staphylococcal nuclease, each of which has a single Trp residue planted at an internal site. The studies on Trp fluorescence, ANS-binding fluorescence, far- and near-UV CD spectra, and enzymatic activity are carried out. It is found that the mutation at the hydrophobic core of protein generates molten globular state conformation, which is a loose structure compared to their original compactness in wild type (WT). Its enzyme activity and surface hydrophobicity are also affected. The studies show that by proper site designing and external binding, Trp mutagenesis is a suitable method for carrying out the study on site specified dynamics of proteins. [ABSTRACT FROM AUTHOR]

Internal solvation of protein was studied by site-directed mutagenesis, with which an intrinsically fluorescent probe, tryptophan, is inserted into the desired position inside a protein molecule for ultrafast spectroscopic study. Here we review this unique method for protein dynamics research. We first introduce the frontiers of protein solvation, site-directed mutagenesis, protein stability and characteristics, and the spectroscopic methods. Then we present time-resolved spectroscopic dynamics of solvation dynamics inside cavities of active sites. The studies are carried out on a globular protein, staphylococcal nuclease. The solvation at sites inside the protein molecule’s cavities clearly reveals characteristics of the local environment. These solvation behaviors are directly correlated to enzyme activity. [ABSTRACT FROM AUTHOR]