Spontaneous Parametric Down-Conversion Induced by Non-Degenerate Three-Wave Mixing in a Scanning MEMS Micro Mirror

Area of Science:

• Micro-electro-mechanical systems (MEMS)
• Nonlinear dynamics
• Optics

Background:

• Scanning micro-mirror actuators are silicon-based MEMS devices crucial for automotive LIDAR and consumer projection.
• Typically, MEMS designs aim for a single high-Q drive mode for resonant excitation.
• Unexpected nonlinear phenomena can compromise device performance and reliability.

Purpose of the Study:

• To investigate the observation of resonant three-mode excitation in MEMS micro-mirror actuators.
• To elucidate the underlying physical mechanisms, specifically spontaneous parametric down-conversion.
• To develop a comprehensive model explaining the observed nonlinear dynamical behaviors.

Main Methods:

• Experimental observation of resonant three-mode excitation.
• Theoretical analysis of three-wave coupling induced by geometric nonlinearities.
• Modeling of Duffing-type nonlinearities and associated dynamical behaviors.
• Numerical emulation of experimental findings using a fundamental model.

Main Results:

• Demonstration of spontaneous parametric down-conversion leading to resonant three-mode excitation.
• Identification of geometric nonlinearities as the origin of three-wave coupling.
• Observation of diverse nonlinear dynamics, including bifurcations and amplitude modulations.
• Validation of a single fundamental model capable of explaining all experimental results.

Conclusions:

• Spontaneous parametric down-conversion, a nonlinear optical phenomenon, occurs in MEMS micro-mirrors due to geometric nonlinearities.
• This three-wave coupling, combined with Duffing nonlinearities, leads to complex dynamical behaviors.
• Understanding the conditions for three-wave down-conversion is critical for MEMS design to prevent functional failure and fracture.