Chaos and bifurcation in the vibration of a metal cantilever excited by a modulated pulsed laser

Laser-induced vibration is a promising principle of actuation for its energy conversion from optical to mechanical. The nonlinearity of the optical-thermal-mechanical coupling leads to a narrow drive bandwidth in the high vibration mode and limits its applications to conventional micrometer level. In this study, a mathematical model coupling the photothermal effect and the thermoelastic effect has been derived. The numerical calculation shows that the vibration of the cantilever exhibits chaos, bifurcation and modal interaction as the modulated frequency changes, indicating the potential excitation strategy that we can take advantage of these nonlinear states to enhance the energy efficiency beyond micrometer-scale actuation. We propose a new excitation method to enhance the energy efficiency enabling the generation of millimeter-scale vibrations with a single-point pulsed laser. The nonlinearity of cantilever vibration can be further enhanced by controlling the pulse laser frequency, driving the system from stable state to chaos and bifurcation, which leads to increased amplitude and energy efficiency. Compared to stable state, chaos and bifurcation can amplify the amplitude of the cantilever by 5 to 10 times, respectively, with a maximum amplitude of 0.69 mm and 2.31 mm in experimental validations. This allows the laser induced excitation to offer the potential for widely using in non-destructive testing, precision operations, and driving micro-resonators.