Abstract: Manganese dioxide (MnO2) is a widely used and well-studied 3-dimensional (3D) transition metal oxide,
which has advantages in ultrafast optics due to large specific surface area, narrow bandgap, multiple
pores, superior electron transfer capability, and a wide range of light absorption. However, few studies have
considered its excellent performance in ultrafast photonics. γ-MnO2 photonics devices were fabricated
based on a special dual-core, pair-hole fiber (DCPHF) carrier and applied in ultrafast optics fields for the
first time. The results show that the soliton molecule with tunable temporal separation (1.84 to 2.7 ps) and
600-MHz harmonic solitons are achieved in the experiment. The result proves that this kind of photonics
device has good applications in ultrafast lasers, high-performance sensors, fiber optical communications,
etc., which can help expand the prospect of combining 3D materials with novel fiber for ultrafast optics
Abstract: We report on an ultrafast nonequilibrium phase transition with a strikingly long-lived martensitic anomaly driven by above-threshold single-cycle terahertz pulses with a peak field of more than 1 MV/cm.A nonthermal, terahertz-induced depletion of low-frequency conductivity in Nb3Sn indicates increased gap splitting of high-energy Γ12 bands by removal of their degeneracies, which induces the martensitic phase above their equilibrium transition temperature. In contrast, optical pumping leads to a Γ12 gap thermal melting. Such light-induced nonequilibrium martensitic phase exhibits a substantially enhanced critical temperature up to ∼100 K, i.e., more than twice the equilibrium temperature, and can be stabilized beyond technologically relevant, nanosecond time scales. Together with first-principle simulations, we identify a compelling terahertz tuning mechanism of structural order via Γ12 phonons to achieve the ultrafast phase transition to a metastable electronic state out of equilibrium at high temperatures far exceeding those for equilibrium states.
Abstract: The gamma-ray vortex burst in the nonlinear Thomson scattering when the laser wakefield accelerated electron bunch collides with an ultra-intense Laguerre–Gaussian laser that was reflected from the refocusing spiral plasma mirror. The orbit angular momentum of the scattering laser would be transferred to the gamma radiation through the scattering process. The 3-dimensional particle-in-cell simulations gave the electron dynamics in the scattering, which determines the characteristics of the vortical radiation. The radiation calculation results illustrated the burst of gamma-ray vortex and surprisingly revealed the radiation pattern distortion phenomenon due to the nonlinear effect. This scheme can not only simplify the experimental setup for the generation of twisted radiation but also boost the yield of vortical gamma photons. The peak brightness of the gamma-ray vortex was estimated to be 1 × 1022 photons/s/mm2/mrad2/0.1% BW at 1 MeV, which might pave the way for the researches on angular momentum-related nuclear physics.
Abstract: The fabrication of high-resolution laser-scribed graphene devices is crucial to achieving large surface areas and thus performance breakthroughs. However, since the investigation mainly focuses on the laser-induced reduction of graphene oxide, the single-beam scribing provides a tremendous challenge to realizing subdiffraction features of graphene patterns. Here, we present an innovative 2-beam laser scribing pathway for the fabrication of subdiffraction graphene patterns. First, an oxidation reaction of highly reduced graphene oxide can be controllably driven by irradiation of a 532-nm femtosecond laser beam. Based on the oxidation mechanism, a 2-beam laser scribing was performed on graphene oxide thin films, in which a doughnut-shaped 375-nm beam reduces graphene oxide and a spherical 532-nm ultrafast beam induces the oxidation of laser-reduced graphene oxide. The spherical beam turns the highly reduced graphene oxide (reduced by the doughnut-shaped beam) to an oxidized state, splitting the laser-scribed graphene oxide line into 2 subdiffraction featured segments and thus forming a laserscribed graphene/oxidized laser-scribed graphene/laser-scribed graphene line. Through the adjustment of the oxidation beam power, the minimum linewidth of laser-scribed graphene was measured to be 90 nm. Next, we fabricated patterned supercapacitor electrodes containing parallel laser-scribed graphene lines with subdiffraction widths and spacings. An outstanding gravimetric capacitance of 308 F/g, which is substantially higher than those of reported graphene-based supercapacitors, has been delivered. The results offer a broadly accessible strategy for the fabrication of high-performance graphene-based devices including high-capacity energy storage, high-resolution holograms, high-sensitivity sensors, triboelectric nanogenerators with high power densities, and artificial intelligence devices with high neuron densities.