A High-Speed Chip-Scale Rotary Polygon Optical Scanner Based on a Micromotor Integrated With a Micro-Polyhedron Mirror

Micro-opto-electro-mechanical systems (MOEMS) based mirrors with a suitable actuation range are often used for optical beam scanning applications. While several MOEMS scanners have been reported, they often have limitations with respect to their range of motion, field of view, mass, size and fabrication cost. In this work, we present a rotary micro-polygon scanner based on an electrostatic variable capacitance micromotor for laser beam steering applications. The miniaturized scanner consists of a hollow micro-polyhedron mirror with a base radius of
$200 {\mu }\text{m}$
and a height of
$400 {\mu }\text{m}$
. It is mounted on the rotor of a variable capacitance micromotor using an epoxy-based adhesive. The rotor has a diameter of
$600 {\mu }\text{m}$
and is
$2.5 {\mu }\text{m}$
thick. The micromotor was fabricated using a commercial three-layer polysilicon surface micro-machining process (PolyMUMPs) and the micro-polyhedrons were fabricated using a commercial bulk micro-machining process (PiezeoMUMPs). After fabrication of the components, the micro-scanner was assembled and operated under atmospheric conditions using a three-phase square wave excitation ranging from 0 V to 200 V and achieved rotational speeds of up to 2100 rpm. An optical laser beam with a wavelength of 632 nm was reflected off the sidewall of the rotating micro-polyhedron, achieving an experimentally measured scanning angular range of 57.88°, an angular scan rate of 220 radians per second and a scan speed of 25,200 lines per minute or 420 lines per second with a 12 sided micro-mirror. The ratio of the output power over the input optical power is measured over a scanning range of 22°, which is limited by the size of the photo-detector, yielding a ratio spanning from 0.18 to 0.22. This rotary micro-scanner can provide high scanning speeds and a wide scanning field of view with a footprint of 1.25 mm
²
and a thickness of 0.83 mm, which is suitable to implement chip-level high-performance micro-beam steering systems for various applications. [2022-0020]