Design, simulation and characterization of a MEMS optical scanner

This paper reports on the design, simulation and opto-electro-mechanical characterization of a microelectromechanical system (MEMS) scanner actuated by an out-of-plane (vertical) electrothermal actuator that was fabricated using a single layer silicon-on-insulator (SOI) foundry process. The overall size of the scanner, including the micromirror and the actuator, is 2 mm × 1 mm. A maximum static mechanical tilting angle of 5° is achieved at a dc driving voltage of 18 V and current of 23 mA, corresponding to a 10° optical scan angle. The scanner can be operated from dc to low frequencies (the 3 dB bandwidth is from 0 Hz to 80 Hz), which meets the requirement for certain practical opto-electronic systems such as optical coherence tomography (OCT) systems. The scanner has a maximum mechanical tilting angle of 8° at its resonant frequency of 2.19 kHz, corresponding to a total of 16° maximum optical scan angle. Simulations of static and dynamic performances of the scanner have been conducted using finite element method (FEM) software, resulting in outcomes similar to the experimental findings. A thermal response time of 60 ms is calculated numerically using heat flow theory, while a thermal response time of 55.6 ms was experimentally obtained by analysing the intensity distribution of the scanned patterns generated when using a square driving waveform to drive the scanner.