Phonon-cavity electromechanics

Photonic cavities have emerged as an indispensable tool to control and manipulate harmonic motion in opto/electromechanical systems(1). Invariably, in these systems a high-quality-factor photonic mode is parametrically coupled to a high-quality-factor mechanical oscillation mode(2-12). This entails the demanding challenges of either combining two physically distinct systems, or else optimizing the same nanostructure for both mechanical and optical properties(4-11). In contrast to these approaches, here we show that the cavity can be realized by the second oscillation mode of the same mechanical oscillator(13,14). A piezoelectric pump(15,16) generates strain-induced parametric coupling between the first and the second mode at a rate that can exceed their intrinsic relaxation rate. This leads to a mechanically induced transparency in the second mode which plays the role of the phonon cavity(17,18), the emergence of parametric normal-mode splitting(19,20) and the ability to cool the first mode(2-11). Thus, the mechanical oscillator can now be completely manipulated by a phonon cavity(21).