Frequency Comb With High Tunability via Coexistence State Excitation and Cavity Modulation in Microelectromechanical Resonators

The modulation of phononic frequency comb (PFC), as a ruler of frequency, is complex and flexible via different pump methods and microelectromechanical systems (MEMS) devices. This article reports a new approach for achieving high tunability in PFC generator through the excitation of the coexistence state and cavity modulation. A novel visualized multiple-dam model elucidates the behavior of comb generation. By analyzing the effects of pump frequency and pump intensity, it is revealed that the coexistence state is fundamentally governed by degenerate four-wave mixing (FWM), a principle shared with the normal state. Operating the resonator in the coexistence state enables the generation of a greater number of frequency combs using the same pump intensity. This leads to an enhanced repetition rate of the comprehensive combs, facilitating the encoding of multiple information and fostering more pronounced wave interactions. In addition, a cavity-modulation approach is introduced through the manipulation of dc bias voltage, allowing for improving the tunability of frequency comb. The utilization of MEMS electrostatic resonators in achieving this phenomenon holds promise for various applications in frequency spectroscopy, tunable calibrated measurement, and encryption engineering. The coexistence state and cavity modulation pathways represent an important advancement in understanding the mechanisms and characteristics of PFC generation and interaction.