Scanning Micro-Mirror with an Electrostatic Spring for Compensation of Hard-Spring Nonlinearity

Area of Science:

• MEMS (Micro-Electro-Mechanical Systems)
• Optics and Photonics
• Nonlinear Dynamics

Background:

• Scanning micro-mirrors often exhibit nonlinear spring behavior due to torsion-bar effects, leading to issues like hysteresis and instability.
• The 'hard-spring effect' in torsion bars causes increased stiffness with larger rotation angles, degrading performance.
• Existing micro-mirror designs face challenges with nonlinearity, limiting their operational range and precision.

Purpose of the Study:

• To investigate the compensation of the hard-spring effect in scanning micro-mirrors.
• To introduce and validate the use of an electrostatic-comb spring for nonlinearity mitigation.
• To enhance the stability and symmetry of micro-mirror oscillation curves.

Main Methods:

• Theoretical analysis of nonlinear spring dynamics.
• Fabrication of a silicon-on-insulator scanning micro-mirror with actuator and compensation combs.
• Experimental testing in vacuum and atmospheric conditions to evaluate compensation effectiveness.

Main Results:

• The electrostatic-comb spring effectively compensates for the hard-spring effect of the torsion bar.
• The oscillation curve of the micro-mirror becomes more symmetric at resonant frequencies.
• Compensation was achieved by applying DC voltage to the electrostatic-comb spring, demonstrating its soft-spring effect.

Conclusions:

• Electrostatic-comb springs offer a viable method for compensating hard-spring nonlinearities in scanning micro-mirrors.
• This compensation technique improves the linearity and stability of micro-mirror operation.
• The developed micro-mirror design shows potential for enhanced performance in various optical applications.