Theoretical framework to design and optimize feasible all optical modulator based on multi passband slit array filters in frequency domain

• Proposing a multi-passband all-optical modulator based on slit array structures, exhibiting very high energy efficiency, perfect modulation depth, and high transmittance ratio. • Proposing a customized method for increasing its modulation efficiency using an anti-reflecting coating technique. • Proposing a realizable fabrication method utilizing silicon deep reactive ion etching and copper electroplating. • Proposing an improved circuit model to account for the effect of incident angle and accelerate the optimization process. • Investigation of the all-optical modulation performance of the device under illumination by an 800 nm laser pump. • Investigation of the plasmonic nature of the resonance by analyzing the resonance field distribution. Driven by the urgent need for high-performance optical filters and modulators in THz communication and imaging systems, this paper proposes an energy-efficient, high-modulation-depth all-optical modulator based on a plasmonic silicon-core slit array structure, along with methods for its design, fabrication, and optimization. The design process for tuning the number, resonance frequencies, amplitudes, and quality factors of the transmission passbands was based on a hybrid genetic particle swarm algorithm, employing both finite element method (FEM) and circuit modeling. The proposed closed-form circuit model accurately captured the effects of the oblique incident angle and the coating layers. The modulation performance of the structure was enhanced using a matrix formulation method for layered media, incorporating an anti-reflective coating. Subsequently, the modulation performance was analyzed using FEM simulations in the frequency domain. The proposed modulators show promise for applications in next-generation communication systems and terahertz imaging.