Phononic frequency comb in carbon nanotube mechanical resonators at very high frequency band

As a typical optical measurement technique, the optical frequency comb plays an irreplaceable role in spectroscopy and precision measurement. Recently, the concept of frequency combs has been adapted to the phononic domain, leading to the development of phononic frequency combs (PFCs), which have been utilized in various micro-mechanical systems. However, the realization of PFCs in flexural vibration resonators within the very high frequency (VHF) band – crucial for applications in communications and information processing – remains unachieved. In this study, we report the realization of PFC in carbon nanotube (CNT) mechanical resonators operating within the VHF band for the first time. Additionally, we observe that the system exhibits novel frequency combs and nonlinear enhancement in a two-mode mechanical resonator. Due to the broadband operation, tunable modulation depth, as well as easy fabrication and integration of one-dimensional carbon nanotubes, our investigation into PFCs within the VHF band holds promise for advancing classical and quantum precision measurement techniques, while also deepening our comprehension of nonlinear physics.