Robust and Compact Electrostatic Comb Drive Arrays for High-Performance Monolithic Silicon Photonics.

Area of Science:

• Microelectromechanical Systems (MEMS)
• Photonics
• Nanotechnology

Background:

• Actuating stiff monolithic photonic components like slab waveguides demands significant force.
• Existing actuation methods face constraints from actuator footprint size and fabrication process limitations.
• Increasing actuator complexity to meet force requirements is often infeasible due to space and design restrictions.

Purpose of the Study:

• To develop an electrostatic comb drive actuator capable of high force output without increasing footprint.
• To optimize actuator design for maximum force intensity while maintaining necessary travel range.
• To address fabrication challenges and ensure design robustness for silicon photonics applications.

Main Methods:

• Utilized arrays of electrostatic comb drives with optimized repeating cell geometry.
• Focused optimization on finger geometry, finger arrangement, and arm design (number of fingers, arm length).
• Validated the co-optimized unit cell against an asymmetric slab waveguide load using analytical modeling, numerical simulation, and experimental measurement.

Main Results:

• Achieved a maximum pre-pull-in force intensity of approximately 342 N/m² at 70 V.
• Maintained a travel range of about 6 µm.
• SEM analyses and correction functions confirmed close matching between theoretical models and experimental data, demonstrating design robustness.

Conclusions:

• The optimized electrostatic comb drive actuators effectively increase force output without compromising travel range or stability.
• The design overcomes key space and fabrication constraints for actuating monolithic photonic components.
• These actuators are highly suitable for optical beam steering in in-plane silicon photonics and optical microsystems.