Nonlinear response of very high frequency contour mode resonators

Area of Science:

• Materials Science
• Electrical Engineering
• Physics

Background:

• Aluminum Nitride Contour Mode Resonators (CMRs) are crucial for Very High Frequency (VHF) applications.
• Understanding nonlinearities in CMRs is essential for optimizing their performance and exploring new functionalities.

Purpose of the Study:

• To identify the sources of nonlinearities in VHF Aluminum Nitride CMRs.
• To model these nonlinearities using both physical and electrical circuit approaches.
• To demonstrate the application of these nonlinearities for frequency comb generation.

Main Methods:

• Experimental characterization of 225 MHz CMRs under varying RF power.
• Development of a modified Butterworth-Van Dyke (MBVD) circuit model incorporating nonlinear elements.
• Finite-element method (FEM) based full-wave numerical simulations to isolate nonlinear mechanisms.
• Analysis of the relationship between variable damping, geometric nonlinearities, and resonator quality factor (Q).

Main Results:

• Identified self-heating-induced nonlinear stiffness and geometric nonlinearity-induced variable damping as primary sources of resonance red-shift.
• Established a linear correlation between the variable damping coefficient and the resonator's Q factor.
• Validated the MBVD model and FEM simulations against experimental data.
• Successfully generated frequency combs in high-Q CMRs.

Conclusions:

• Nonlinearities in VHF AlN CMRs are well-understood and modeled.
• The findings provide guidelines for analyzing and designing nonlinear CMRs.
• Exploiting these nonlinearities enables novel applications like MHz frequency comb generation for advanced telecommunications and sensing.