Open AccessDynamical behavior of ultra-short laser pulse in a cascade three-level molecular system
Author(s) -
Ji-Cai Liu,
Zhao Ke,
Yuzhi Song,
ChuanKui Wang
Publication year - 2006
Publication title -
wuli xuebao
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.199
H-Index - 47
ISSN - 1000-3290
DOI - 10.7498/aps.55.1803
Subject(s) - pulse (music) , physics , laser , dipole , bloch equations , rotating wave approximation , envelope (radar) , excitation , discrete dipole approximation , atomic physics , amplitude , materials science , molecular physics , optics , condensed matter physics , quantum mechanics , quantum , telecommunications , radar , detector , computer science
We study the interaction between the ultra-short laser pulses and the one-dimensional symmetrical π conjugated molecular material (4,4′-bis (dimethylamino) stilbene) by solving Maxwell-Bloch equations. This kind of molecular material has strong nonlinear optical properties, and its electronic structures and dipole moments are calculated by use of density functional theory on ab initio level. The numerical results show that the slowly varying envelope approximation and the rotating wave approximation cannot accurately describe the propagation properties of the ultra-short pulse in the molecular medium. In the case of single photon resonance, the two-level model can well describe the interaction between the small area pulse and the molecular system. For large area pulse, due to the existence of strongly secondary excitation to the higher-lying levels, the three-level model should be used. When the amplitude of the incident electric field is kept constant, the third level's population increases with the increase of the pulse area.