Quantification of antagonistic optomechanical forces in an interferometric detection system for dynamic force microscopy

In fiber-optic interferometer systems detecting oscillatory cantilever motion, the intensity distribution of the light field in the interferometric cavity generates an optomechanical coupling determining the effective properties of the oscillating system. For a low finesse cavity established by an uncoated cantilever and the fiber end, the resonance frequency and spring constant are shifted mainly due to radiation pressure whereas the Q-factor is varied due to photothermal forces under typical conditions. We find, that radiation pressure and photothermal force act in opposite directions and discuss the retardation times governing the antagonistic effects differing by orders of magnitude. (C) 2010 American Institute of Physics. [doi:10.1063/1.3509412]