Low-loss and high-resolution mechanical mode tuning in microspheres

Lack of tunability impedes the wide application of optomechanical systems; however, little research exists on mechanical frequency tuning. Herein, ultra-fine low-loss dynamical mechanical frequency tuning is achieved by compressing a microsphere along the axial direction. The tuning resolution reaches approximately 4% of the mechanical linewidth, and the variation range of the mechanical quality factor (Q_m) is within 2.9% of the untouched Q_m. The roles of geometric deformation, spring effect, and stiffness were also evaluated through simulation and experimental analysis. Furthermore, sine function modulation was displayed, with a Pearson coefficient exceeding 99.3%, to achieve arbitrary-function mechanical resonance tuning. This method paves the way for scalable optomechanical applications, such as mechanical vibration synchronization or optomechanics-based optical wavelength conversion.