Torsion Mirror Research Articles

Mechanical and optical properties of surface micromachined torsional mirrors in silicon, polysilicon and aluminum

This paper presents a comparative study of surface micromachined structures fabricated in three different materials, using torsional micromirrors as test vehicle. The devices are realized in single-crystal silicon, polycrystalline silicon and aluminum. Mechanical properties such as internal strains, sticking phenomena, yield strains and endurance test resistance as well as optical properties such as surface reflectivities and scattering characteristics are investigated on the devices. the characterization points out that the silicon and polysilicon structures present higher yield strains and are less prone to surface sticking while the aluminum mirrors have higher surface refiectivities.

Electrostatic micromechanic actuators

Actuators based on the electrostatic principle are one of the most important in microsystem technology. In the future, actuators of 1D or 2D type will be necessary in many fields, especially in optical deflection and scanning systems. They will solve many different problems: device fabrication processes, surface-deformation, reflection factors, optimization of movement, electrical drive and reliability. Micromechanic electrostatic torsional mirrors are described showing swivel angles up to 30 degrees .

Surface micromachined scanning mirrors

Both aluminum cantilever and torsional scanning mirrors have been fabricated and their static and dynamic properties are studied experimentally and theoretically. The experiments showed resonance frequencies in the range of 163 kHz – 632kHz for cantilever beams with Q values between 5 and 11. Torsional mirrors showed resonance frequencies in the range of 410 kHz – 667 kHz with Q values of 10 – 17. All measurements performed at atmospheric pressure. Both types of mechanical structures were deflected electrostatically at large angles (± 5°) more than 10 11 times without breaking and without any noticeable deterioration due to fatigue. A number of different light modulator arrays made up of adjacent devices was investigated and the measured performance parameters were in good agreement with calculations.