High-Performance SOI-Based Filter with Multiple Microring Resonators for Telecom Applications: Design, Fabrication, and Characterization

In this paper, we present the design, simulation, fabrication, and characterization of a high-performance all-optical filter. It consists of three cascaded microring resonators and four integrated grating couplers, developed for precise wavelength selection within the telecom band (1500–1600 nm). The device was fabricated on a silicon-on-insulator platform using high-resolution electron beam lithography and encapsulated with a silica cladding layer to enhance mechanical robustness and increase the effective refractive index, resulting in superior optical performance. A fundamental aspect of the proposed design is systematic geometrical tailoring of critical parameters, including ring radius, waveguide width, coupling gap, coupling length, and the number of cascaded resonators, to allow precise control over the filter’s spectral characteristics. The fabricated filter achieves an ultra-narrow passband of 1.99 nm, a resonance power transfer efficiency exceeding 56%, and a Q-factor up to 804. The free spectral range (FSR) is shown to be design-dependent, varying between 27 nm and 37 nm as a function of ring radius, thus enabling flexible specification during the design phase. Experimental characterization using tunable lasers showed strong agreement with finite-difference time-domain simulations, validating the filter design. Extensive parametric studies were conducted to evaluate the influence of structural variations on key performance metrics, including resonance wavelength, Q-factor, transmission efficiency, and FSR. The proposed filter demonstrates outstanding spectral resolution, low insertion loss, and excellent efficiency, establishing it as a promising solution for advanced optical communications, high-precision photonic signal processing, and emerging nanophotonic systems.