▎ 摘　　要

Here, a novel graphene-based square ring resonator is proposed to design 2-channel and 4-channel demultiplexer. Compared to typical ones, graphene demultiplexers are a better performer and recently considered as a highly promising candidate for low footprint and minimum crosstalk purposes. By introducing such a unique gradient, the plasmon resonances of the demultiplexer are directly excited and resonant wavelength tuning is achieved. To validate the performance of the proposed demultiplexer, coupled-mode theory is used to examine the structure theoretically. We demonstrate through simulations that the simulation results are in good agreement to the theoretical ones. The minimum crosstalk -48.12 dB and -34.13 dB with an average -38.44 dB and -27.12 dB are achieved and the mean spectral bandwidth, quality factor and power transmission efficiency 303.5 nm and 308.75 nm, 30.04 and 28.62, 60.5% and 47% are computed, respectively for 2-channel and 4-channel demultiplexers. These values are very suitable for photonic integrated systems in the mid-IR regime.