Open AccessPolarization-based tachometer for measuring spinning rotors
Author(s) -
Émilien Prost,
E. Hertz,
F. Billard,
B. Lavorel,
O. Faucher
Publication year - 2018
Publication title -
optics express
Language(s) - Uncategorized
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.26.031839
Subject(s) - optics , physics , polarization (electrochemistry) , spinning , angular momentum , harmonics , circular polarization , tachometer , linear polarization , resolver , angular velocity , high harmonic generation , elliptical polarization , superposition principle , laser , materials science , classical mechanics , voltage , rotor (electric) , chemistry , quantum mechanics , detector , composite material , microstrip
We report on the polarization analysis of shortpulse ultraviolet radiation produced by third-harmonic generation in a gas of coherently spinning molecules. A pulse of twisted linear polarization imprints a unidirectional rotational motion to the molecules leading to an orientation of their rotational angular momenta. A second pulse, time-delayed with respect to the first one, circularly polarized in the plane of rotation of the molecules, acts as a driving field for third-harmonic generation. The angular momentum and energy conservation applied to this process foresees the generation of two Doppler-shifted circularly-polarized harmonics of opposite handedness. Our analysis reveals that spinning molecules enable the generation of a well polarized third-harmonic radiation exhibiting a high degree of ellipticity. Tracking the orientation of the latter allows a time-capture of the molecular axis direction from which the average angular velocity of the rotating molecules is inferred. This method provides a user-friendly polarization-based tachometer for measurement of the rotational speed of spinning nonlinear rotors.