Enhanced narrow-bandwidth emission during high-order harmonic generation from aligned molecules

Abstract

We theoretically investigate the selective enhancement of high-harmonic generation (HHG) in a small spectral range when an orthogonal-polarized two-color laser field interacts with aligned O(2) molecules. It is shown clearly that the enhanced narrow-bandwidth emission near the cutoff of the HHG spectrum can be effectively controlled by the molecular alignment angle, laser intensity and the relative phase of two-color laser fields. Furthermore, the strong dependence of narrow-bandwidth HHG on molecular alignment angle indicates that it encodes information about O(2) molecular orbitals, so it may be an alternative method for reconstruction of O(2) molecular orbitals.

High-Order Above-Threshold Ionization Using a Bi-Elliptic Orthogonal Two-Color Laser Field with Optimal Field Parameters

“…In addition to the interaction with the bicircular field, strong-field processes in the presence of the orthogonal two-color (OTC) field have been studied in recent years [21][22][23][24][25][26][27][28][29][30][31][32][33]. The OTC laser field is a superposition of two mutually orthogonal linearly polarized fields having the angular frequencies rω and sω, with r and s integers.…”

Alignment Thresholds of Molecules

“…Molecular alignment in moderately intense laser fields has been the focus of interest for over two decades, both for its fundamental value and for a large variety of applications, including enhancement of high harmonic generation [1,2], orbital imaging [3][4][5][6][7], investigation of orientation dependent ionization rates and patterns [8][9][10][11][12][13], control of laser filamentation [14][15][16], development of long range order in molecular assembly [17], control of electron and energy transfer [18], and more. The mathematical framework for describing molecular alignment by moderately intense laser fields in both adiabatic (long pulse) and nonadiabatic (short pulse duration compared to the rotational periods) was developed in the mid 1990's [19,20] and was since extended, generalized and applied in a vast number of experimental and numerical publications [21][22][23].…”