• photothermal forces
• optical cavity
• cooling
• bistability
• non-linear effect
• optomechanics
• polymer
• nanomembrane
• membrane

The emerging fields of cavity optomechanics explores the interaction between electromagnetic radiation and nano or micromechanical motion. The variety of experimental systems and possible applications range from gravitational-wave interferometry to the experimental demonstration of the quantum ground state of a mechanical resonator, from ultrasensitive measurement to fundamental questions in quantum physics.
Optomechanical interaction are mediated by radiation pressure or photothermal forces. In our experiment we focused on the latter in the case of a Fabry-Pérot hemiconfocal cavity, where the plain mirror of the cavity was a polymer coated nanomembrane. Starting from the build up and configuration of the whole apparatus, we have been studying the bolometric effect for two different laser wavelengths, that is for two different absorption rates of the polymer, as well as the transmission and reflection properties of the membrane. Working in the high vacuum regime we moved on to the study of the actual optomechanical phenomena: we have been able to observe cooling effects on the first normal mode of the membrane and we have studied the dynamics of nonlinear effects typical of a slow-fast systems.