Enhancing amplitudes of higher-order eigenmodes of atomic force microscope cantilevers by laser for better mass sensing

Abstract

We theoretically study the dynamics of an atomic force microscope cantilever under various irradiation configurations of a laser. By conveying a stream of photons and its momenta, the laser beam whose geometrical intensity profile has a Gaussian form will exert a nonuniform radiation pressure on the cantilever surface and modify its vibration. The dependences of cantilever modeshapes on the laser spot position and waist reveal a possibility of diminishing or exciting a specific eigenmode. For cantilevers of ∼200 µm length, the vibration amplitude of higher-order eigenmodes can be increased 4–5 times. This implies the change in cantilever effective mass once the interaction with the ambient is taken into account. The study gives a deeper understanding of soft cantilever dynamics in liquids and can be applied in the modern measurement configuration where high frequencies are required.