Two-Decade-Wide Dense Phononic Frequency Combs in a Linear MEMS Resonator Using Analog Feedback

Phononic frequency combs (PFCs), featuring a series of equally spaced spectral lines, has emerged as a potential technique for precision timing, sensing and metrology. The generation of PFCs based on MEMS resonators typically rely on nonlinear mode coupling, which complicates both design and fabrication. Here, we report a novel PFCs generation method with a linear piezoelectric MEMS resonator using an analog nonlinear feedback circuit, which transforms the linear device to a nonlinear Van der Pol-Duffing (VDPDF) system. The result exhibits that nonlinear frequency mixing occurs in this linear resonator, leading to the emergence of dense PFCs, and is also consistent with simulation predication. The evolution of PFCs and corresponding comb spaces are studied, showing that the feedback-based approach provides access to generate highly tunable PFCs with a range spanning two decades, offering an effective and versatile solution for customizing PFCs.