Dipolar effects on propagation of ultrashort laser pulse in one-dimensional para-nitroaniline (pNA) molecules
2005 (English)In: Journal of Physics B: Atomic, Molecular and Optical Physics, ISSN 0953-4075, E-ISSN 1361-6455, Vol. 38, no 23, 4235-4245 p.Article in journal (Refereed) Published
The dynamic behaviour of ultrashort (femtosecond) laser pulses in a molecular medium is studied by solving the full Maxwell-Bloch equations beyond the limits of the slowly varying envelope approximation and the rotating-wave approximation under the resonant and the non-resonant conditions. A one-dimensional asymmetric charge-transfer molecule, para-nitroaniline, is used as a model molecule whose electronic properties are calculated with the time-dependent hybrid density functional theory. Under the one-photon resonant condition, 4 pi pulse is separated into two sub-pulses. The weight of the second-harmonic component mainly contributed by the two-photon excitation becomes stronger with longer propagation time. Under the two-photon resonant condition, the separation of 4 pi pulse is not induced and many higher-order spectral components beyond the second-harmonic generation occur. Interestingly, when the pulse propagates for long enough, the carrier modification becomes so significant that a continuous spectrum is generated. The Fourier transform of the high-harmonic spectrum demonstrates that an even shorter laser pulse can be produced in both resonant and non-resonant propagations. The effects of permanent dipole moments on the pulse evolution are discussed.
Place, publisher, year, edition, pages
2005. Vol. 38, no 23, 4235-4245 p.
femtosecond optical pulses, high-harmonic-generation, 2-photon absorption, attosecond pulses, 2-level medium, light, media, hyperpolarizability, density, moments
IdentifiersURN: urn:nbn:se:kth:diva-15299DOI: 10.1088/0953-4075/38/23/006ISI: 000234355100010ScopusID: 2-s2.0-28344449188OAI: oai:DiVA.org:kth-15299DiVA: diva2:333340
QC 201005252010-08-052010-08-05Bibliographically approved