Tunable MOEMS Microring Resonator Based on in-Plane Bending Through Rotary Comb Drives

Photonic integrated circuits (PICs) are experiencing a period of rapid transformation, driven by an increased demand for optical devices that are more efficient and compact. Programmable photonic technologies are at the center of this transformation, offering unparalleled versatility for applications in optical communication, sensing, and computational systems wherein components such as ring resonators assume a pivotal role. These devices enable precise wavelength filtering and spectral manipulation, making them indispensable for applications such as wavelength-division multiplexing (WDM), optical switching, and reconfigurable photonic circuits [1]. However, traditional tuning mechanisms for such devices, such as thermo-optic or carrier-injection methods, often encounter challenges like high power consumption, thermal crosstalk, and limited scalability [2]. These inherent limitations restrict their applicability within densely integrated photonic systems. In addressing these challenges, Micro-Opto-Electro-Mechanical Systems (MOEMS) have emerged as a potential solution. Leveraging mechanical actuation, MOEMS technology offers a low-power, compact, and highly precise alternative for dynamic reconfiguration of photonic devices [3]. The proposed device is a compact and energy efficient MOEMS compatible with Silicon-on-Insulator (SOI) technology, consisting of a voltage-controlled, mechanically tunable add-drop ring resonator for optical telecommunications. The optical properties of the ring can be tuned applying a voltage to two electrostatic actuators, designed as rotary comb-drives sketched as in fig. 1a. Electrostatic and mechanical analyses have been performed using COMSOL Multyphysics to understand the bending properties of the system; photonic analyses have been carried out using Ansys Lumerical to observe the shifts of the resonant frequencies of the micro-ring. Silicon waveguides having widths of 200 μm and thicknesses of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$400 \mu \mathrm{m}$</tex>, with 100 nm of spacing in the input-ring and ring-output coupling areas, and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{T}\mathrm{M}_{11}$</tex> as the guided mode were considered. The outcome of the investigation, plotted in Fig. 1b, shows the ability of the system to shift the ring resonant frequency of 6.81 nm and 11.66 nm with 1 V and 2 V of in-plane bending voltage, respectively. As a result, the MOEMS ring opto-electro-mechanical sensitivity is equal to 5.83 nm/V, which is two orders of magnitude greater than other voltage-controlled microring layouts recently proposed in literature [3]–[5]. The reported results confirm the effectiveness of the proposed device as a highly sensitive and highly efficient voltage-controlled tunable photonic element. The ability to achieve significant wavelength shifts with such low voltage inputs makes this device suitable for applications requiring wide dynamic range, high versatility and simple design, being compatible with single-mask SOI technology, such as reconfigurable optical communication networks and programmable photonic circuits.