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Flexural Cavity Mechanics in Electrostatically Driven 1D Phononic Crystal

Vishnu Kumar, Bhargavi B. A., Saurabh A. Chandorkar

Abstract

Phononic Crystals provide a versatile platform for controlling phonons in applications such as waveguiding, filtering, and sensing. To minimize dissipation, cavity resonators are often embedded within the bandgap of phononic crystals and integrated with suitable transduction techniques. Here, we demonstrate one-dimensional (1D) phononic transmission using electrostatic transduction, enabling the realization of high-quality mechanical oscillators. Using a double-ended tuning fork resonator embedded in a 1D phononic crystal, we observe degenerate flexural modes (in-phase and out-phase) exhibiting enhanced and comparable quality factors within the same device due to mode degeneracy. The in-phase mode, whose frequency lies inside the phononic bandgap, shows an approximately two-fold increase in quality factor compared to an anchored resonator, while this enhancement diminishes for the out-phase mode (frequency outside the bandgap) at temperatures where thermoelastic dissipation is negligible. This approach offers a promising route toward low-loss, encapsulated phononic devices for sensing and signal processing applications.

Flexural Cavity Mechanics in Electrostatically Driven 1D Phononic Crystal

Abstract

Phononic Crystals provide a versatile platform for controlling phonons in applications such as waveguiding, filtering, and sensing. To minimize dissipation, cavity resonators are often embedded within the bandgap of phononic crystals and integrated with suitable transduction techniques. Here, we demonstrate one-dimensional (1D) phononic transmission using electrostatic transduction, enabling the realization of high-quality mechanical oscillators. Using a double-ended tuning fork resonator embedded in a 1D phononic crystal, we observe degenerate flexural modes (in-phase and out-phase) exhibiting enhanced and comparable quality factors within the same device due to mode degeneracy. The in-phase mode, whose frequency lies inside the phononic bandgap, shows an approximately two-fold increase in quality factor compared to an anchored resonator, while this enhancement diminishes for the out-phase mode (frequency outside the bandgap) at temperatures where thermoelastic dissipation is negligible. This approach offers a promising route toward low-loss, encapsulated phononic devices for sensing and signal processing applications.
Paper Structure (1 equation, 4 figures, 1 table)

This paper contains 1 equation, 4 figures, 1 table.

Figures (4)

  • Figure 1: Phononic crystal design: (a) unit cell construction, resonating beam 1 $\&$ 2 coupled with coupling beam, the periodic boundary condition (PBC) is applied in the direction of wave propagation and anchor acts as a fixed boundary condition; (b) spring-mass system configuration; (c) optical image of the PnC device; (d) analytically calculated dispersion curve shows the first two bandgaps; (e) COMSOL simulated dispersion curve and transmission
  • Figure 2: Transmission characterization of PnC: (a) the measurement setup, (b) the measured transmission along with the simulation. VNA: Vector Network Analyzer, TIA: Trans-Impedance Amplifier, and PS: Power Supply
  • Figure 3: Anchor Resonator: (a) the measurement schematic with the resonator design, (b) The frequency response of the resonator shows two degenerate modes: the low-frequency (in-phase) mode and the high-frequency (out-phase) mode, and COMSOL simulation of the resonator corresponding to the degenerate modes.
  • Figure 4: (a) anchored resonator near the silicon CTE temperature, the in-phase mode has a higher quality factor than the out-phase mode, (b) cavity resonator, the in-phase has a higher Q than the out-phase and two times the anchored resonator.