Design and Control of an Analog Optical Switch Based on the Coupling of an Electrothermal Actuator and a Mass-Spring System

Extending the analog output function has become an important trend in current MEMS optical switches. The electrothermal actuator is a potential candidate for realizing the analog optical switch since the output displacement can be continuously controlled throughout its driving range. However, since most existing micromirrors employ the out-of-plane motion, which is directly driven by the actuator, the design flexibility is limited and the temperature effect cannot be ignored. In this article, an analog optical switch is designed based on the coupling of an electrothermal actuator, a mass-spring system, and a sidewall reflective optical path. The in-plane reciprocating motion of the sidewall reflection micromirror is realized through the coupling, with the load analysis of the optical switch being significantly simplified. A temperature decrease as high as 305.5 K can be achieved by the integration at an applied voltage of 15 V. The dynamic coupling mechanism is well explained by a multibody electro-thermal-mechanical model. Furthermore, a position sensorless control scheme is proposed to realize the analog output function and anti-interference of the coupling optical switch. The linear analog output is presented throughout the micromirror's displacement of 0-90.57 μm. We believe that this work is significant for providing a novel functional device in intelligent optical window, laser ignition system, optical neural computing, etc.