Optical excitation of micro-mechanical resonators

The authors present theoretical and experimental studies on optothermal excitation of bending-mode micromechanical resonators. The theory results in a prediction of induced bending moment (modulus and phase) as a function of the excitation frequency, the geometry of the structure, and material properties. It is shown that decisive roles are played by the absorption length of the material μ, the penetration depth of a thermal wave δ, and the thickness of the resonator. δ is a function of the excitation frequency while the resonance frequency depends on h. The theory results in design rules for optothermal resonators. It is shown that absorbing layers improve the efficiency of the optothermal transduction only in the case of transparent materials. Experiments agree well with theory