All-optical logic gates based on three-dimensional asymmetry modulation: from coherent absorption to dynamic key mapping encryption

Many studies have explored functionalized all-optical logic gates for multidimensional processing of optical signals. However, most of these studies focus on single-input-output (SIO) operations, which limit the dynamic switching capabilities of the devices. In this study, we propose a stack-based reconfigurable split ring resonator (SRR) metamaterial structure for constructing all-optical logic gates. This design breaks the three-dimensional symmetry of the structure to excite the Fano resonance absorption peak at a communication wavelength of 1.55 μm, and combines it with the principle of coherent perfect absorption (CPA) to demonstrate nearly 100% output modulation capability. The designed logic gates are insensitive to incident bias and stable under varying light intensities. High-contrast XOR, OR, and AND logic functions can be realized by setting specific thresholds. The multiple-input-output (MIO) feature presented in this paper is not limited to allowing multiple input-output signals to interact; it also enables the system to combine the near-field modulation capability of the asymmetry factor with the output modulation capability of the phase-difference factor, allowing for switching between different logic output modes. Furthermore, we connect optical signal processing to encrypted communication, proposing a dynamic key mapping (DKM) encryption scheme based on this MIO property in combination with the traditional Chinese <i>Ba-Gua</i> theory. This breaks through the limitations of traditional one-time password (OTP) encryption and opens up new possibilities in digitized metasurface optical computing, optical encryption, and information security.