Within the frame of electrodynamic and nonlinearly Thomson scattering, we study the initial phase-sensitivity with respect to spatial characteristics of a static electron irradiated by Guassian linearly polarized few-cycle laser pulse for different beam waists. With the combination and comparison of the electron's real-time motion and radiation conditions, the initial phase-sensitivity turns out with inverse proportional relation to the beam waist where the radiation’s transverse shift of varied initial phases is irregular in the non-tightly focused case. Furthermore, by changing the initial phases, the petal-like full spatial radiation pattern changes from 4 unstable pieces to 2 constant pieces and the radiated energy shift slows down with the beam waist evolving from b0 = 1 to b0 = 10. Finally, with initial phase 𝜙0 increasing from 0 to π we discover an interesting phenomenon for the first time, where the normalized maximal radiated power and corresponding azimuth angle fluctuate in the form of ripples and ladders in tightly-focused case b0 = 1, in contrast to the perfectly symmetry with respect to φ0 = 0.5π for the maximal radiated power in non-tightly focused case b0 = 10.
Hybrid plasmonic waveguides (HPWs) have become a hot topic in nanophotonic due to their excellent optical field constraints and low propagation loss. Based on the polarization dependence of surface plasmon polariton (SPP) excitation the symmetry of cylindrical vector beams, a cylindrical hybrid plasmonic waveguide (CHPW) realizing limited propagation and two tapered hybrid plasmonic waveguides (THPWs) achieving nanofocusing are presented. CHPW supports radial polarization mode and well compensate mode propagation loss by adjusting the structural parameters of the waveguide. Splendid mode limitation and long transmission distance with low loss can be achieved simultaneously. On the basis of CHPW, the structure is tapered to realize nanofocusing. And periodic grooves are constructed on the metallic surface of the tapered hybrid plasmonic waveguide (THPW) to meet the phase matching condition and maximize the coupling of light energy from inside to outside. Meanwhile, the low index layer of THPW is replaced with two different index layers, which is broadened to gather more energy efficiently and the energy is converged on the apex of the waveguide to form the ultrahigh field enhancement, which is another optional way to improve the performance of THPW. The results offer vital reference value for designing and manufacture related photonic devices.
This work reports a graphene cylindrical hybrid plasmonic waveguide (GCHPW) consisting of a high-index dielectric core, a sandwiched low-index dielectric layer and a single layer graphene. Unlike traditional metallic cylindrical hybrid plasmonic waveguide (CHPW), GCHPW’s advance is that the nano-thickness light field can be significantly enhanced in the sandwiched low-index dielectric layer and the graphene interface, and a superior performance is achieved. Furthermore, the electromagnetic parameters of graphene is tunable, and the mode properties of the waveguide depend on the structural parameters, so the mode area and transmission distance can be flexibly optimized by adjusting these parameters. TM01 mode with radially polarized transverse component is supported in the novel GCHPW, and a more compact confinement of light field is achieved. Additionally, the GCHPW has a smaller size compared with the CHPW. This study provides a valuable reference for design of graphene plasmonic waveguides and offers a new way for the limited transmission of radially polarized light.
A conical hybrid plasmonic probe (CHPP) for ultrahigh field enhanced nanofocusing with lower loss is demonstrated. The CHPP consists of two different low-index dielectric layers sandwiched between a high-index conical core and a silver cladding. Properties of nanofocusing are analyzed by finite element method, under illumination of a radially polarized beam at a wavelength of 632.8 nm. The numerical results prove that, by introducing the additional lower-index layer, the whole low-index dielectric region is broadened to collect more energy efficiently, and the energy is converged on the apex of the CHPP to form the ultrahigh field enhancement. Compared with the traditional hybrid plasmonic probe, the optimized CHPP exhibits lower loss and higher field enhancement of 1771 times. The thickness and refractive index of the lower-index layer are discussed for optimizing the structure. The results indicate that the CHPP has a simple structure with excellent performance, which has important potential applications in relevant fields, particularly in nanotechnology of field enhancement. This work also provides a convenient way for designing and optimizing hybrid plasmonic structure.
The spatial, temporal and spectral emission characteristics of radiation generated from electron oscillations driven by an intense circularly polarized laser pulse have been investigated theoretically and numerically using a single electron model. The motion of an electron is highly relativistic and head-on (180° ) collision of a single counter streaming electron and an intense circularly polarized laser pulse can produce a single ultrashort zeptosecond pulse along θ = 90° by merely using a few-cycle laser pulse with fixed carrier-envelope phase offset Φ0 = 0 without controlling phase φin [5] which is defined as the phase of the laser pulse when the electron enters it. An interesting modulated structure of the spatial characteristic is observed and analyzed.
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