All-optical logic gates using E-shaped silicon waveguides at 1.55 μm

Owing to the advanced fabrication technology of silicon, silicon waveguides are particularly attractive for implementing all-optical signal processing devices and switches. Therefore, in this paper, a silicon-on-silica waveguide that consists of four slots arranged in the shape of letter E is proposed to be employed as the building block for simulating fundamental all-optical logic gates (AOLGs), including XOR, AND, OR, NOT, NOR, NAND, and XNOR, at 1.55 μm telecommunications wavelength. The operation concept of these logic gates relies on the constructive and destructive interference that results from the phase difference induced by optical beams that are incident on the E-shaped waveguide. The performance of the target logic gates is assessed against the contrast ratio (CR) metric. Moreover, the dependence of the spectral transmission on the device's key operating parameters is investigated and assessed. Compared to other reported designs, the results obtained by conducting simulations using the finite-difference-time-domain in lumerical commercial software show that the proposed waveguide can operate at a higher speed of 80 Gb/s and attain higher CRs of 36, 39, 35.5, 28.8, 30, 38, and 36.7 dB for logic XOR, AND, OR, NOT, NOR, NAND, and XNOR, respectively. This suggests that by using the proposed scheme, AOLGs could be realized more feasibly with greater performance and faster operation toward satisfying the present and future needs of light wave circuits and systems.