Hao Chen

Simultaneous realization of large-angle beam steering and dynamic focusing within a single micro-electromechanical system (MEMS) remains a significant challenge. Inspired by the human eyes, we propose an aluminum nitride (AlN) piezoelectric micromirror that integrates tip, tilt, piston, and varifocal capabilities into a single device. The micromirror consists of a 1.0 × 1.0 mm varifocal plate driven by four decoupled actuating beams. Experimentally, the device exhibits an optical scanning angle of 12°/7.5° at the resonant frequency of 2.6 kHz, effectively covering the primary human visual field with rapid spatial tracking. The resonant piston displacement of 48 µm at 1.68 kHz facilitates high-speed phase modulation and active optical stabilization. Meanwhile, it demonstrates a focal tuning range from 39 mm to 45 mm under static (DC) operation. Remarkably, the micromirror achieves a dynamic varifocal response time of 1.7 ms, providing instantaneous focal transitions that are approximately 100 times faster than the biological accommodation of the human eye. Combining a human-like field of view with ultra-fast actuation speeds, this low-cost, compact AlN micromirror holds great potential as a core component for biomimetic machine vision and wearable optics.

MEMS mirror-based Fourier transform spectrometers (FTS) are powerful in various portable or embedded applications. However, the small scanning range of MEMS mirrors seriously limits MEMS-FTS’ spectral resolution. In this work, a dual-MEMS-mirror FTS (DMM-FTS) is proposed that immediately doubles the scanning range and thus improves the spectral resolution by a factor of two. The employed MEMS mirrors are uniquely designed electrothermal MEMS mirrors that can generate a maximum vertical displacement as large as 260 µm. Experimental results demonstrate that this DMM-FTS achieves a stable optical path difference up to 783 µm at a record level. Meanwhile, the maximum dynamic tilt of both MEMS micromirrors is controlled within ±0.004°. Consequently, the developed DMM-FTS achieves a remarkable spectral resolution of 0.5 nm at a wavelength of 532 nm, or 18 cm ⁻¹ . The mechanical architecture and control strategy of this DMM-FTS are compatible with both near-infrared and mid-infrared systems. This design delivers prominent improvements in spectral analysis performance and holds great potential for various on-site or in-line real-time monitoring applications.

Piezoelectric MEMS micromirrors for light modulation and optical beam steering have been drawing extensive attention recently, but their applications are still limited due to low fill factor and low resonant frequency, especially when the well-established piezoelectric material–AlN is employed. This study proposes a bow-shaped unimorph piezoelectric actuator that can generate multidegree-of-freedom motion with high fill factor. Particularly, a tip-tilt-piston (TTP) piezoelectric micromirror made of such actuators is designed, fabricated, and characterized. The fill factor is as large as 73% with a mirror plate size of $1.0\times 1.0$ mm. The measured resonant frequencies for the piston, tip, and tilt modes are 0.890, 1.747, and 1.781 kHz, respectively. The measured maximum piston stroke and tip or tilt angle reach $3.3~\mu $ m and 14.4 mrad with high linearity under 24 V_pp. This bow-shaped actuator design provides a new direction for enhancing piezoelectric actuation efficiency and capability.