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RESEARCH PRODUCT

Ultrafast optics in coherently spinning molecules

subject

description

This thesis reports on the study of unidirectional rotation of molecules and focuses on the rotational Doppler effect occuring in the course of third-harmonic generation in coherently spinning molecules.The rotational Doppler effect appears when a circularly polarized wave interacts with an anisotropic rotating object. During the interaction, an exchange of angular momentum and energy between the field and the object occurs, leading to a frequency shift of the wave. In this work, the frequency shift of the third-harmonic generated in unidirectionaly rotating molecules has been observed. An anlytical model developped in the mansucript forsees four kinds of frequency shifts depending on the mutual handedness of the circular polarization of the fundamental and harmonic fields and the handedness of the rotating molecules. The four shifts have been measured in third-harmonic generation in unidirectionaly rotating molecules of O2, N2, and CO2. A thorough study of the rotational Doppler effect and the underlying physics has been conducted. A polarization analysis of the third-harmonic produced in coherently spinning molecules has also been done, showing the high degree of ellipticty of the harmonic. From this polarization analysis, the orientation of the molecular axis can be retrieved, providing a new way to measure the angular frequency of rotating molecules.