Optical cavity back action on an AFM microlever
Résumé
Two back action processes generated by an optical cavity based detection device can deeply transform the dynamical behavior of an AFM microlever: the photothermal force or the radiation pressure. Whereas noise damping or amplifying depends only on the detuning inside the cavity for radiation pressure back action, we present experimental results carried out under vacuum and at room temperature on the photothermal back action process which appears to be much more complex. We show for the first time that it can simultaneously act on two vibration modes in opposite direction: noise on one mode is amplified whereas it is damped on another mode. Modelisation of this effect leads us to conclude that indeed it is specific to photothermal back action and cannot be observed in case of radiation pressure back action.
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