All-optical reconstruction of three-band transition dipole moments by the crystal harmonic spectrum from a two-color laser pulse

Abstract

When a bulk solid is irradiated by an intense laser pulse, transition dipole moments (TDMs) between different energy bands have an important influence on the ultra-fast dynamic process. In this paper, we propose a new all-optical method to reconstruct the k-dependent TDMs between multi-bands using a crystal high-order harmonic generation (HHG). Taking advantage of an obvious separation of bandgaps between three energy bands of an MgO crystal along the <001 > direction, a continuous harmonic spectrum with two plateaus can be generated by a two-color laser pulse. Furthermore, the first harmonic platform is mainly dominated by the polarization between the first conduction band and the valence band, and the second one is largely attributed to the interband HHG from the second conduction band and the valence band. Therefore, the harmonic spectrum from a single quantum trajectory can be adopted to map TDMs between the first, second conduction bands, and the valence one. Our work is of great significance for understanding the instantaneous properties of solid materials in the strong laser field, and will strongly promote the development of the HHG detection technology.

On the (un)importance of the transition-dipole phase in the high-harmonic generation from solid state media

“…These observation may have important impact on some applications of solid-state HHG, such as Berry curvature measurement [9]. For example, all-optical bandreconstruction [4,5] and dipole-reconstruction [7] methods tend to utilize a one-dimensional picture of the reciprocal space by selecting a presumably dominant contribution to the process [6] in order to extract information concerning the material band-structure. In contrast, here we have seen how the HHG-source can "light up" the Brillouin zone in rather non-intuitive patterns.…”

“…High-harmonic generation in solid-state media has been studied with keen interest ever since the first observations a decade ago [1] followed by experiments with many different materials and structures [2,3]. Mediated by the light-matter interactions at high density, the phenomenon opens a new window into the dynamics of the solid-state medium at attosecond time-scales, including all-optical reconstruction of the band structure [4][5][6], mapping of the transition-dipole moments [7], characterization of higher-order nonlinearity [8], and measurements of Berry curvatures [9].…”

Investigation of the Spatio-Temporal Characteristics of High-Order Harmonic Generation Using a Bohmian Trajectory Scheme

“…High-order harmonic generation (HHG) can be created by ultrafast intense laser fields interacting with gas atoms [1][2][3][4][5], molecules [6][7][8][9][10][11], and solids [12][13][14][15]. As harmonic energy rises, the intensity of harmonic emission develops a distinct "platform" structure.…”

Amplitude and rotation of the ellipticity of harmonics from a linearly polarized laser field

“…The interaction of high-intensity laser pulses with atoms or molecules leads to a series of nonlinear phenomena, [1][2][3] such as multiphoton ionization (MPI), [4,5] nonsequential double ionization, [6,7] above-threshold ionization, [8][9][10][11] Coulomb explosions, [12,13] and high-order harmonic generation (HHG). [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] HHG is an effective means to obtain desktop shortwave coherent radiation source, and its spectral range has expanded from infrared to extreme ultraviolet band and across the soft x-ray (1 nm-30 nm) band.…”