Sustained mechanical self-oscillation of carbon nanotube cantilever by phase locked loop with optomechanical heterodyne

Abstract

We have proposed an optomechanical heterodyne method for measurements of carbon nanotube (CNT) cantilever vibrations and demonstrated the sustained mechanical self-oscillation of the CNT cantilever by the combination of the phase locked loop and the proposed method. Mass sensitivities less than 100 zg were easily achieved in vacuum for long term (∼100 s) deviation and even in air for short term (∼1 s) deviation. Furthermore, the CNT cantilever with the phase locked loop detection is achieved with the very high force sensitivity of a force gradient of ∼10−10 N/m, which is fifth orders magnitude higher than that for the conventional noncontact atomic force microscopy.