Wavelength dependence of high-order-harmonic yield in inhomogeneous fields

Abstract

We theoretically investigate the wavelength dependence of the HHG yield in spatially inhomogeneous fields with few-cycle laser pulses. The results show that the HHG yield first decreases with a slower scaling λ −4 as the increase of the laser wavelength compared with λ −5 in homogeneous fields. However, with the laser wavelength further increased, an inflection of wavelength appears and then the HHG yield presents an upward trend. Based on the electron trajectories analysis, we demonstrate that the decrease in the scaling law λ −4 mainly results from the cutoff extension in inhomogeneous fields. And the uptrend in HHG yield is attributed to the increasing wavelength-dependent ionization rate of the additional quantum path that dominates the harmonic generation. In addition, the carrier-envelope phase dependence of the wavelength-dependent HHG yield is also investigated.

Comparison of high harmonic generation and attosecond pulse from 3D hydrogen atom in three kinds of inhomogeneous fields

“…In our calculation, we set the radial grid points N = 1200 and partial wave L = 120, and spatial grid sizes r max = 170 a.u., which is equal to the experimental setup value of the nanostructure consisting of bowtie-type gold pads separated by an air gap g = 18 nm [29]. We choose a one-color laser field and a two-color laser field, which can be expressed as:…”

“…After that, some alternative approaches to realize plasmonic field enhancement were explored by employing different kinds of metallic nanostructures [16,17]. Subsequently, there is a lot of theoretical work [18][19][20][21][22][23][24][25][26] on the characteristic of HHG and attosecond pulse generation of atoms in inhomogeneous field, such as the coherent extreme ultraviolet photons generation beyond the carbon K edge [27], the extension of plateau [28,29], quantum path control [30], wavelength and carrier-envelope phase dependence [31], above-threshold ionization process [32,33], and so on. Most of theoretical study is based on linear-form inhomogeneous electric field, and the comparation between linear-form and polynomial-form fields still needs further investigation.…”

Theory of harmonic generation from the hydrogen molecular ion in an inhomogeneous laser field

“…From this it is possible to achieve fine control over the electronic and nuclear dynamics in molecular dissociative state [23]. Lu laser pulses [25,26]. Moreover, they theoretically investigate the HHG from Rydberg atoms in the inhomogeneous field [27].…”

High-order-harmonic generation from Rydberg atoms driven by plasmon-enhanced laser fields

“…Due to such field gradient and the electron confinement into a small volume, the conventional Keldysh picture of strong-field physics -in which the spatial dependence of the laser field and the influence Coulomb potential is ignored-is incapable to fully explain the underlying physics [18][19][20]. As a result, there has been an intense effort to comprehend both the underlying physics at the microscopic level and to numerically simulate the processes at a multi-scale level [16,[20][21][22][23][24][25][26][27][28][29][30]. Elucidating the mechanisms behind plasmon-enhanced HHG are thus essential due its potential technological applications, e.g.…”

“…However, in many theoretical studies, Eq. (9) has been shown to be sufficient to elucidate the underlying physics of the problem of interest [16,[20][21][22][23][24][25][26][27][28][29][30].…”