MEMS mirrors submerged in liquid for wide-angle scanning

This paper reports an electrothermal MEMS scanning mirror working in liquid for the first time. By submerging the MEMS mirror into a mineral oil whose refractive index is 1.47, a wide-angle optical scan (>120°) was achieved at small driving voltage (<10V), and the scan frequency reached up to 30 Hz. The wide angle was achieved because of the angular increase of the “Snell's Window” effect and the large mechanical tilt angle (±18°) of the MEMS mirror as well. The power consumption is 9.9 mW/° when working in air and 11.7 mW/° in the mineral oil. This submerged optical scanner may enable many new applications of wide-angle optics.