Mohammad Reza Rakhshani

We present a one-dimensional dimer grating structure based on a diamond-like carbon (DLC) trapezoidal bar array on a SiO ₂ –Au substrate. Numerical analysis reveals that the structure exhibits a narrow guided-mode resonance (GMR), enabling strong field confinement and suppression of radiative losses. The resonance exhibits a full width at half-maximum (FWHM) of 0.48 nm at a wavelength of 1037 nm, corresponding to a quality factor of Q =2143. The device demonstrates high sensing performance, characterized by a bulk refractive index sensitivity of 334 nm/RIU, a figure of merit (FOM) of 2570RIU ⁻¹ , and a surface sensitivity of 0.76 nm/nm. The practical applicability of the proposed sensor is validated through modeling of nanometer-thick protein layer detection in a physiologically relevant environment, where the resonance exhibits a clear spectral shift. These simulation results indicate the strong potential of the designed device for label-free biochemical sensing, environmental monitoring, and medical diagnostics.

In this research, a narrowband metamaterial absorber (MA) is designed using a cascaded ring resonator (RR) with a Metal–Insulator–Metal (MIM) structure. Conventional design methodologies such as finite-difference time-domain (FDTD) method often rely on trial-and-error simulations, which are both computationally intensive and time-consuming. To address this challenge, we present a design framework based on the Adaptive Neuro–Fuzzy Inference System (ANFIS). This hybrid approach, which combines neural networks and fuzzy logic, offers a cost-effective and time-efficient alternative to FDTD optical simulations. This type of hybrid network is recognized for its capability to represent highly nonlinear and complex samples. To predict the absorption through the ANFIS, four geometrical parameters of the structure have been utilized as input variables. The performance of this model is assessed by employing a root mean square error (RMSE) and mean absolute error (MAE) as a criteria for the evaluation, with two membership functions (MF) and a 5-fold cross-validation. The RMSE (0.0811) and MAE (0.062) indicate that absorption can be predicted with high precision. Based on our results, ANFIS achieves approximately 90% time savings compared to the conventional FDTD method, while maintaining acceptable prediction accuracy. Furthermore, the comparison of our method with Random Forest and k-Nearest Neighbor (KNN) shows that ANFIS yields lower prediction error. The results indicate that the proposed MA can achieve nearly perfect absorption at specific values of the geometrical parameters. As a key application, the proposed structure has been utilized as a sensor. The optimal results for two key factors are a sensitivity of 600 nm per refractive index unit (RIU) and a full-width at half-maximum (FWHM) of 4 nm. Due to its compact size, perfect absorption, and tunability, the proposed MA offers diverse applications in solar cells, sensors, and stealth technology.

Miniaturization of terahertz (THz) absorbers is crucial for advancing compact and efficient electromagnetic (EM) devices. This study investigates the impact of various spoof plasmon topologies T-slot, grating, and L-slot on the miniaturization and performance of THz metamaterial absorbers (MAs). The proposed designs utilize dual-ring and single-ring gold structures on a quartz spacer. Our structures demonstrate up to 15% size reduction while maintaining high absorption rates (96%–98%). The L-slot topology exhibits optimal performance with absorption peaks at 0.758 and 0.984 THz (dual ring) and 1.00 THz (single ring), compared to the conventional design’s 0.77-/1.15- and 1.14-THz resonances, respectively. Comprehensive analyses reveal that spoof structures significantly alter phase response, modify group delay characteristics, and enhance electric field distribution uniformity across the resonator surface. The coupled mode theory (CMT) model accurately predicts these behaviors with parameters extracted from simulation results.

All-optical logic gates (AO-LGs) are key elements that play a pivotal role in the development of future all-optical computing and all-optical computers. In this paper, benefiting from particle swarm optimization (PSO), an optimized metasurface unit cell in the far-infrared (FIR) frequency band is presented as the basis of four port controlling light with the light system. This system, known as coherent perfect absorption (CPA), could be applied as AO-LGs in certain conditions. NOT, AND, OR, NAND, NOR, XOR, and XNOR logic gates can be implemented with the proposed method. The remarkable innovation of this article is the use of a fuzzy inference system (FIS) instead of a crisp threshold. Different calculated parameters like extinction ratio (ER = 96.2 dB), contrast ratio (CR = 99.54 dB), amplitude modulation (AM = 0.7 dB), and eye-opening (EO = 99%), besides the possibility of utilizing the proposed system for various kind of CPA films, prove the impressive effects of FIS applying as a novelty in this work. Small dimensions and low power consumption are other characteristics of the proposed method that are obtained as a result of using optimized metasurface-based CPA.