Microelectromechanical systems (MEMS)-based tuning methods offer promising solutions for dynamically controlling optical properties in photonic integrated circuits (PICs) to address the limitations associated with traditional approaches that rely on direct modulation of the material’s refractive index. Conventional methods such as thermo-optic, plasma dispersion, and electro-optic modulation, face significant challenges including high energy consumption, limited refractive index change, and issues with heat dissipation and optical losses. By contrast, MEMS-based actuators directly reposition optical components, enabling reduced device footprints, negligible static power consumption, rapid response times, and improved reliability. This paper systematically explores the operating principles and design characteristics of five representative MEMS actuator technologies widely used in tunable waveguide devices: In-plane comb-drive actuators, cantilever actuators, gap-reducing actuators, vertical digital actuators, and vertical comb-drive actuators. Each actuator type is analyzed for its distinct advantages and challenges, with considerations such as device compactness, switching speed, voltage requirements, and robustness against reliability issues such as pull-in phenomena and stiction. The insights presented emphasize the substantial potential of MEMS-based tuning methods to advance the scalability, energy efficiency, and performance of next-generation PICs. Continued research into improving actuator performance, including increased operation speed, lower operating voltages, and further miniaturization, will be critical to achieving widespread integration and adoption.
