Research On Unidirectional Reflectionless And Switching Applications In Multilayer Metallic Metamaterials

As an emerging medium for information transfer,photons are rapidly developing and widely used due to their advantages of fast transmission speed,high communication capacity,high security,long signal transmission distance and low data loss.Metamaterials are good carriers for the study of photonic information transfer because of their specially designed microstructures that can efficiently regulate and manipulate light transmission.In the field of optics,unidirectional reflectionless transmission,a special optical phenomenon based on quantum PT symmetry theory and metamaterials,is expected to be the basis for optical communications,biosensors,surface plasma lithography,nanometer photonic devices and integrated circuits.The article proposes a non PT symmetric metal metamaterial scheme that achieves unidirectional reflectionless in both single and dual frequency bands,and provides numerical calculation results.The physical mechanism of its generation is studied using scattering matrix and transfer matrix theory;We also studied the design scheme of photon switches based on metal metamaterials and refractive index voltage adjustable materials,and evaluated the parameter indicators of photon switches.The main work includes:1.We design a non PT symmetric bilayer heterogeneous metallic metamaterials constructed from silver and gold discs and a photopolymer PC.By adjusting and optimizing the distance between the bilayer metal resonators,a bidirectional unidirectional reflectionless at wavelengths 766.8 nm and 785.7 nm is obtained when incident light is incident from the +Z and-Z directions,and a unidirectional perfect absorption is also obtained at the reflectionless point.In addition,using scattering and transmission matrix theory,it is concluded that unidirectional reflection-free transmission occurs at the point where the eigenvalues of the scattering matrix of the system merge;when unidirectional reflectionless transmission occurs in the system,the induced currents of both resonators are in phase;and when compared with the resonator parameters at the reflectionless point,the larger the change in resonator radius,the smaller the peak of the reflection contrast ratio and the further away from the unidirectional reflectionless point.The design of the bilayer heterogeneous metallic metamaterial is not only unaffected by the polarization of the incident light,but also allows for manufacturing process errors while maintaining unidirectional transmission performance.2.We design a non PT symmetric multilayer heterogeneous metallic metamaterial constructed from silver discs,gold discs and gold discs and photopolymer PC.By adjusting and optimizing the distance between two adjacent metallic resonators,a unidirectional double-band unidirectional reflectionless transmission is achieved at wavelengths 737.1 nm and 756.8 nm when the light wave is incident from the +Z direction,and a double-band unidirectional perfect absorption is also obtained at the two reflectionless points.Similarly,the scattering and transmission matrix theories were used to derive that the double-band unidirectional reflectionless transmission occurs at the point where the two eigenvalues of the system’s scattering matrix merge;when the system experiences double-band unidirectional reflectionless transmission,the induced currents of the two adjacent resonators are in phase with each other.The difference in wavelength between the two unidirectional reflection-free points of the designed multilayer heterogeneous metallic metamaterial is less than 20 nm,which has potential applications in realizing unidirectional devices at nanoscale close to multiple points or even a certain bandwidth..3.Based on the designed bilayer and multilayer metallic metamaterials,we have designed two nanoscale photonic switches by introducing a refractive index voltage-tunable organic DAST crystal material.The double-layer metal photonic switch is made by incorporating an organic DAST crystal in the central between the double-layer metallic metamaterials.Two sets of two switching points were obtained at wavelengths of 776.8 nm and 783.6 nm and at wavelengths of 773.6 nm and 787.4 nm,respectively,when adjusting the DAST applied bias voltage equal to ±5 V and ±10 V.The maximum modulation depth of the four switching points was 100% and the minimum insertion loss was 0.71 d B,the performance index of the double-layer metal photonic switch is excellent and has strong practical value.The three-layer metal photonic switch is a three-layer metallic metamaterial with an organic DAST crystal in the central between two adjacent resonators.In the adjustment of the upper and lower DAST plus bias voltage value of only +10 V,and are equal to +24V can be achieved at wavelengths of 757.9 nm,779.5 nm,805.1 nm and 836.9 nm multi-band photonic switching characteristics,the maximum modulation depth of the four photonic switching points is 98.55%,the minimum insertion loss is 0.70 d B,multi-layer metal photonic switch not only excellent performance,but also more than the double-layer metal photonic switch.The multilayer metal photonic switch not only has excellent performance,but also has two more switching points than the double-layer metal photonic switch,which is more advantageous in practical applications.