THz Response Of Split-Ring-Resonator In Asymmetric Layout

Metamaterial,an artificial electromagnetic material whose physical characteristics can be arbitrarily designed,has become one of the research hotspots in the field of optics and materials due to its design,controllability,and other peculiar physical properties.With the further research in the field of terahertz,the design of metamaterial structures plays a vital role in terahertz applications.Therefore,the design of terahertz coupling modes and efficient slow-light metamaterial structures is terahertz technology.Key research topics in application areas.Based on this research need,we conducted a study on the terahertz spectral response characteristics of split-ring-resonator(SRR)under an asymmetric layout.We use the technical route that combines simulation and experiment to investigate the electromagnetic response characteristics of symmetric local broken metamaterial in the terahertz band.In addition,we have analyzed the physical mechanism of the corresponding terahertz resonance of metamaterials and conducted the research of modulation of slow light based on plasma-induced transparency.This paper introduces the following research content,which can be divided into two parts:The first part is the investigation of terahertz dark mode excited by locally symmetric broken metamaterials.First,we investigated the terahertz electromagnetic response characteristics of a complementary double split-ring-resonator.We keep the structure of one SRR unchanged,introduce a local symmetry break,move the position of the metal junction of the other SRR,and then compare the transmission spectra of the two types of metamaterials,we discovered a novel phenomenon of collapse of the Fano effect.When the structure of the outer SRR is maintained and the metal junction of the inner SRR is moved,the resonance mode of the metamaterial w do not change.Interestingly,when the structure of inner SRR is kept unchanged,the originally symmetric complementary metamaterial with stucture of double SRR intrinsically excited Fano resonance mode will gradually collapse with the movement of the outer ring metal junction.In addition,in the intrinsic Between the Lorentz resonance mode and the Fano resonance mode,a dark mode is excited,and the coupling strength of the dark mode is gradually increased with the asymmetric movement of the metal junction.Secondly,we propose three types of fractal metamaterial based on the circular split resonant ring and perform sample processing and testing.This type of metamaterial is controlled by the two degrees of freedom of the metal junction position and the fractal level.We increase the fractal level of metamaterial,and then rotate the structure of SRR.According to the position of the metal ring of the resonance ring,they are named O-gap,U-gap,and C-gap.When the incident electric field is polarized in the direction of the terahertz wave,the O-gap and U-gap metamaterials excite two intrinsic resonance modes,and the C-gap metamaterial excites only one intrinsic resonance mode.The quality factor of the intrinsic resonance mode also increases with the increase of the level of fractal MMs.When the incident field is a terahertz wave polarized in the y direction and the level is 1,all three types of metamaterials are excited.An intrinsic resonance coupling mode.The transmission spectrum of O-gap type of metamaterials appears with multiple coupling modes as he level of fractal MMs increases.The second part is based on the plasma-induced transparency and the coupling of Fano resonator and Lorentz resonator to the modulation of terahertz slow light.First,we propose a two-layer metamaterial solution with a sandwich structure.Two resonators that resonate with terahertz waves at the same frequency but have very different quality factors are designed on the front and back layors of 2.5um soft substrate made of thick polyimide respectively.Based on the interference effect of bright-dark mode coupling,near this frequency,the transmittance of the incident terahertz wave will increase,thereby inducing the metamaterial transparent,and then leading to a slow light effect.By gradually moving the resonator in the front layer of the metamaterial from top to bottom in parallel,the resulting transparent window undergoes an on-off-on process,and the slow light effect also appears-disappears-appears in the second one.In the slow light area,the slow light value can be adjusted up to 40.4ps.Secondly,based on the coupling effect of the Fano resonator and the Lorentz resonator,we use a double-opened single-ring resonator and a metal strip resonator to couple on a polyimide substrate.The transmission spectrum generated by the split single-ring resonator appears as a Fano line,while the metal strip resonator and the terahertz wave appear as Lorentz lines.We use the same method,keeping the position of the metal strip resonator unchanged,and moving the double-opened single-ring resonator from the top to the bottom.In addition,we changed the positions of two resonators to do the same job.When the metal wire resonator is located on the right side of the double-gap single-ring resonator on the left side,and the double-gap single-ring resonator is moved from top to bottom,the terahertz spectral response characteristics of the metamaterial have not changed physically.On the contrary,after the positions of the resonators are changed,as the resonator moves further,the transparent window in the low-frequency region gradually disappears and gradually appears in the high-frequency region.New transparent window,and the maximum value of the measured data of slow light reaches 34 ps.Finally,we performed a simulation analysis of the coupled physical mechanism behind the transparent windows of all samples.