Study On Unidirectional Reflectionless Property Based On Phase Coupling Between Two Resonators In Metamaterials

Metamaterial is artificial composite on the micrometer or nanometer scale,and the scale of unit cell is smaller than the wavelength of incident wave.Since the prop-erties of metamaterial is mainly determined by the orderly design of material itself at critical physical scales,it has some extraordinary characteristics.For instance,negative refraction,invisibility,electromagnetically-induced transparency,unidirec-tional reflectionlessness,and the like.Wherein the unidirectional reflectionlessness having potential applications in the optical switch,sensor,optical diode and so on.Numerous researches have shown that the quality factor of metal metamaterial is lower due to the larger loss.Therefore,the low-loss silicon is used for resonator and the quality factor is relatively higher.The unit cell of our metamaterial consists of two silicon resonators which embedded in a photopolymer and deposited on a glass substrate.Based on the phase coupling between two silicon resonators,the unidirectional reflectionless phenomena can achieve at the exceptional points.We can achieve controllable unidirectional reflectionless phenomena by adjusting the polarization ? of the incident wave and the distance d between the two resonators.Researches have shown that when d is equal to 1184 nm and 1318 nm,the exceptional points appear at 205.31 THz and 202.25 THz,respectively.The high reflectance reaches 0.8,the low reflectance is close to 0 and the reflectance con-trast ratio is close to 1.When the polarization 9 is equal to 0°,unidirectional reflectionlessness occurs,and the polarization ? is equal to 90°,unidirectional reflec-tionlessness disappears at the exceptional points.Using the transfer matrix method,the results of analytical calculation and numerical simulation are exactly the same.Moreover,the distance between two resonators varies within a approximately range of 150 nm,and unidirectional reflectionless phenomena can be persistent.In addi-tion,unidirectional prefect absorptions are obtained near exceptional point with the high absorbance of?0.99 and high quality factor of?83.