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We have proposed a metallic dipole-ellipsoid-bagel nanostructure, which could effectively control the enhanced plasmonic fields within two-color laser for producing isolated attosecond pulses. This nanostructure enables the multiple resonances leading to broad overall bandwidth, which benefits high harmonic generation (HHG) and the production of isolated attosecond pulses via enhanced plasmonic field. The nanostructure could enhance the field intensity exceed 103 in the volume of 10 × 5 × 5 nm3. The isolated attosecond pulse with a duration of 155 as is obtained in the two-color 15-fs incidence. This nanostructure would benefit for the application of the ultra-sensitive multi-color sensor and isolated attosecond pulses generation.

Silicon dioxide films; radio-frequency magnetron sputtering; annealing temperature Abstract. Silicon dioxide (SiO2) films are fabricated on single crystal silicon substrate by radio-frequency magnetron sputtering (RFMS) technique and annealed in electric furnaces at 800°C and 1180°C to form uniform, transparent and compact silica. The surface morphology and roughness of the films are characterized by an atomic force microscopy (AFM). X-ray diffraction (XRD) is employed to analyze the crystalline of the thin films. The chemical composition after annealing is analyzed using X-ray photoelectron spectroscopy (XPS).

The nucleation and crystallization of Li2O-Al2O3-SiO2(LAS) glass ceramic with one(P2O5, TiO2, ZnF2) and two nucleating agents(P2O5+TiO2, P2O5+ZnF2) are investigated by the differential thermal analysis(DTA)，X-ray diffraction(XRD) and the scanning electron microscopy(SEM). Research results show that the LAS glass ceramic with nucleating agent of P2O5can obtain ideal micro spherical crystal grains and the crystallization behavior can be better controlled.

We have proposed a metallic dipole-ellipsoid-bagel nanostructure for the generation of high harmonics via two-color laser field. Comparing with the case of the one-color field, this nanostructure enables a broader bandwidth and smoother harmonic spectra under the condition of the two-color incidence field, which is in favor of the generation of extreme-ultraviolet (XUV) radiation and isolated attosecond pulses. Numerical techniques are employed to optimize nanoantennas and attain enhanced plasmonic field. The electromagnetic properties of this nanostructure is fully analyzed and discussed. The nanostructure support the highest enhancement fact of 2500 for both of 800-nm and 1500-nm incidence, and effectively enhance the field intensity exceed 10 3 in the volumn of 50×50×50 nm 3 .This nanostructure would benefit for the generation of high-harmonic, extreme-ultraviolet (XUV) radiation via plasmonic enhanced filed in a two-color multi-cycle laser field. This work would have potential application in the ultra-sensitive color sensor and the source of isolated attosecond pulses via multicycle laser.

We theoretically investigate utilizing the enhanced plasmonic fields in metallic nanostructures. Numerical techniques are employed to optimize nanoantennas to attain the enhanced plasmonic fields up to 270. In the volume of 15 × 15 × 30 nm 3 in nanoantenna, the intensity could be enhanced to 1014 W/cm 2 for high harmonic generation (HHG). Optimal conditions for the production of MHz isolated attosecond pulse of 140 attosecond via HHG have been identified. These findings open up the possibility for the development of a compact source of ultrashort XUV pulses with MHz repetition rates. our simulations indicate a potential route towards the temporal shaping of the plasmonic near-field and in turn the generation of single attosecond pulses. Such XUV sources, which may operate at MHz repetition rate, could find applications in high-precision spectroscopy and for spatio-time-resolved measurements of collective electron dynamics on nanostructured surfaces. Moreover, the asymmetric cross nanoantennas is proposed to control the polarizations and select the wavelengths via varying the ratio of nanoantennas and generate the XUV pulse in both polarized direction.

Coherent XUV sources, which may operate at MHz repetition rate, could find applications in high-precision spectroscopy and for spatio-time-resolved measurements of collective electron dynamics on nanostructured surfaces. We theoretically investigate utilizing the enhanced plasmonic fields in an ordered array of gold nanoparticles for the generation of high-harmonic, extreme-ultraviolet (XUV) radiation. By optimization of the chirp of ultrashort laser pulses incident on the array, our simulations indicate a potential route towards the temporal shaping of the plasmonic near-field and, in turn, the generation of single attosecond pulses. The inherent effects of inhomogeneity of the local fields on the high-harmonic generation are analyzed and discussed. While taking the inhomogeneity into account does not affect the optimal chirp for the generation of a single attosecond pulse, the cut-off energy of the high-harmonic spectrum is enhanced by about a factor of two.