Programme

P.2 -- Poster, VCTP-47

Date: Tuesday, 2 August 2022

Time: 08:30 - 10:00

Multiple returns in continuum harmonics of asymmetric molecules in multicycle lasers

Le Thi Cam Tu (1,2), Ngoc-Loan Phan (3,4), DinhDuy Vu (3), Cong Ngo (3,5), Van-Hoang Le (3,4)

(1) Atomic Molecular and Optical Physics Research Group, Advanced Institute of Materials Science, Ton Duc Thang University, Ho Chi Minh City, Vietnam; (2) Faculty of Applied Sciences, Ton Duc Thang University, Ho Chi Minh City, Vietnam; (3) Computational Physics Lab K002, Ho Chi Minh City University of Education, Ho Chi Minh City, Vietnam; (4) Department of Physics, Ho Chi Minh University of Education, Ho Chi Minh City, Vietnam; (5) Department of Physics, University of Paderborn, Warburger Str. 100, D-33098 Paderborn, Germany.

A wide range of continuum harmonics is essential for generating attosecond pulse trains. It is commonly used longer-wavelength lasers to push the cutoff to a higher order. However, this also enhances the contribution of higher-order returns (HOR) in a harmonic spectrum, consequently, potentially affecting the lower bound of the continuum range. It is desired to understand how multiple returns affect the harmonic-spectrum structure and their response to different laser parameters. This report presents the manifestation of multiple returns in the high-order harmonic spectra from CO molecules by numerically solving the time-dependent Schroedinger equation within the single-active electron approximation. Based on the time-frequency analysis [1] and the classical simulation [2], we justify the multiple returns effect and the periodicity of the harmonic spectrum of CO. Furthermore, the time-frequency spectra show that the high-order returns not only are asymmetric regarding the molecular rotation of 180 degrees but also correlate with the first-order returns. Finally, we figure out that one can control the contribution of HOR by breaking the laser symmetry in an appropriate way. References [1] Y.-l. Sheu, L.-Y. Hsu, H.-t. Wu, P.-C. Li, and S.-I. Chu, AIP Advances 4, 117138 (2014). [2] P. B. Corkum, Phys. Rev. Lett. 71, 1994 (1993).

Presenter: Le Thi Cam Tu