Low-voltage, large-scan angle MEMS analog micromirror arrays with hidden vertical comb-drive actuators

This paper reports on novel polysilicon surface-micromachined one-dimensional (1-D) analog micromirror arrays fabricated using Sandia´s ultraplanar multilevel MEMS technology-V (SUMMiT-V) process. Large continuous DC scan angle (23.6° optical) and low-operating voltage (6 V) have been achieved using vertical comb-drive actuators. The actuators and torsion springs are placed underneath the mirror (137×120 μm²) to achieve high fill-factor (91%). The measured resonant frequency of the mirror ranges from 3.4 to 8.1 kHz. The measured DC scanning characteristics and resonant frequencies agree well with theoretical values. The rise time is 120 μs and the fall time is 380 μs. The static scanning characteristics show good uniformity (<±3.2%) for a 1 × 10 array with a mirror pitch of 150 μm. The mechanical crosstalk between adjacent mirrors is less than 37 dB. These micromirror arrays have applications in 1×N wavelength-selective switches and N×N wavelength-selective crossconnects in wavelength-division multiplexing (WDM) networks.