Programme

P.18 -- Poster, VCTP-46

Date: Tuesday, 5 October 2021

Time: 08:30 - 10:00

Stability of even-to-odd ratio to laser intensity and wavelength

Hien T. Nguyen (1,2,3), Ngoc-Loan Phan (4), Kim-Ngan H. Nguyen (4), Van-Hoang Le (4)

(1) University of Science, Ho Chi Minh City, Vietnam (2) Vietnam National University, Ho Chi Minh City, Vietnam (3) Tay Nguyen University, Buon Ma Thuot City, Vietnam (4) Ho Chi Minh City University of Education, Ho Chi Minh City, Vietnam

High-order harmonic generation (HHG) is a nonlinear effect occurring when atoms/molecules interact with an ultrashort intense laser pulse. It is well known that the HHG emitted from polar molecules contains both odd and even harmonics. On another side, the ratio between intensities of the adjacent even and odd harmonics, briefly called the even-to-odd ratio, is an essential quantity related to the molecular asymmetry that makes it a promising tool for tracking molecular asymmetricity and dynamics [1,2]. However, for efficient applications, the even-to-odd ratio must be stable to change laser parameters such as intensity and wavelength. This report presents the study on the stability of HHG emitted from CO molecules interacting with different laser pulses of various intensities and wavelengths. The method of HHG calculation is based on numerically solving the time-dependent Schrödinger equation of the laser-molecule system. To study the stability of the even-to-odd ratio, we pay attention to the classical long and short trajectories of the ionized electron, which both contribute to the harmonics. As a result, we discover that the even-to-odd ratio is quite stable when truncating the long electron trajectories in the HHG simulation. This result is essential for applications, and fortunately, the truncation can be performed theoretically by restricting the absorbing boundary [2,3]. Moreover, the removal of the long trajectories is well known experimentally by the good phase-matching in the HHG measurement [4]. [1] Kim-Ngan Nguyen-Huynh, Cam-Tu Le, Hien T. Nguyen, Lan-Phuong Tran, and Ngoc-Loan Phan, Comm. Phys. 30 (2020), 197. [2] Ngoc-Loan Phan, Kim-Ngan H. Nguyen, Cam-Tu Le, Dinh-Duy Vu, and Van-Hoang Le, Phys. Rev. A 102 (2020), 063104. [3] Shujuan Yu, Bing Zhang, Yanpeng Li, Shiping Yang, and Yanjun Chen, Phys. Rev. A 90 (2014), 053844. [4] P. Rudawski, C. M. Heyl, F. Brizuela, J. Schwenke, A. Persson, E. Mansten, R. Rakowski, L. Rading, F. Campi, B. Kim, P. Johnsson, and A. L’Huillier, Rev. Sci. Instrum. 84 (2013), 073103.

Presenter: Nguyen Thi Hien