Chao Wang

By Chao Wang, Yifan Kang and Yonglin Bai

An attosecond research upsurge has been overwhelmingly rising since the establishment of novel light source—single isolated attosecond laser in extreme ultraviolet/X-ray resulted by strong field high-order harmonics generation (HHG). In this chapter, based on the electrostatic tunneling ionization from Coulomb potential modulation of atoms by strong light field, we scrutinized the intrinsic phase of high-order harmonics and analyzed qualitatively the salient dependence of two mainstream single isolated attosecond pulse generation techniques as polarization gating(PG) and amplitude gating(AG) on carrier-envelope phase (CEP) of femtosecond driving laser. The conclusion is that the optimized CEP corresponding to the highest intensity contrast between the main and sideband attosecond pulses is π/2 and 0 for polarization gating and amplitude gating, respectively. Further, an experimental implementation was given in detail to exemplify the tricks for optimum phase-matching process of HHG from the interaction of high-intensity femtosecond laser field with noble gas target. The effects of the relative location between Gaussian-shaped driving femtosecond laser field focus and the gas target source used on the HHG phase matching were studied, and the conclusion found that the expected position of gas target for optimum phase matching is always lying behind the focal point of the driving field used.

Part of the book: Modern Applications of Electrostatics and Dielectrics

By Yifan Kang, Hongtao Yang, Chao Wang and Wei Zhao

The photoelectron energy spectrometer is known as “fingerprint technology” in atomic and molecular physics, surface science, and other research fields, the core of which is the precise spatiotemporal control of electron packets. Because the scientific issues involved, such as the space charge effect of pulsed electron packets, have not been clearly elucidated, the spectrometer technology with high energy resolution, wide detection range, and high collection efficiency is still unavailable. A novel physical model for analyzing the space charge effect of electron packets, the reduced thin electron disk model (RETED), is proposed. It is found that the initial parameters of the electron packet have complicated coupling effects on its broadening magnitude and that the self-broadening process can be decomposed into an avalanche explosion process and a subsequent quasi-linear spreading. The avalanche explosion occurs within an extremely localized time and space range and is identified as the dominating factor for the electron packet broadening process. To further aim at constructing a set of adiabatic magnetic field architectures suitable for a magnetic-bottle time-of-flight electron energy spectrometer, a practical scheme for a side pole-piece magnetic lens is proposed, and the high peak-valley ratio adiabatic magnetic field is constructed by combining a side pole-piece magnetic lens, a pole-piece permanent magnet, and a solenoid. Finally, a high-performance magnetic-bottle electron energy spectrometer is demonstrated. The maximum detectable electron energy can reach 1000 eV, the full-range relative energy resolution is better than 1%, and the collection solid angle reaches 2π. These results will enrich the theory of high-precision electron energy spectra detection techniques, meeting the urgent demand in such fields as electron momentum spectroscopy (EMS) and photoelectron spectroscopy.

Part of the book: Electromagnetic Field