| Surface plasmon polaritons(SPPs)is a kind of special electromagnetic wave,which is generated at the metal medium interface and propagates along the interface.It is found that SPPs can overcome the limitation of diffraction limit.Therefore,the study of SPPs can effectively promote the further development of optoelectronic devices.There are many types of Surface Plasmonic Waveguides(SPWs)based on SPPs.Among the different types of reported SPWs,Metal-Insulator-Metal(MIM)type SPWs are widely used because it has some significant characteristics such as lower transmission loss,easy to be fabricated and stronger electromagnetic field confinement.Plasmonic induced transparency(PIT)and plasmonic induced absorption(PIA)are two optical effects that can be generated in some types of composite MIM-type surface plasmon optical waveguide structures,which are originated from the destructive of constructive interference between the SPPs field mode propagtated along different paths.Based on the PIT and PIA effects,the studies and disgnes of nanoscale refractive index sensors,filters,optical switches,slow-light and fast-light effects have become a hotspot in recent years.There are three main research contents in this paper:(1)The SPW structure of the end coupled concentric nano-ring resonator is designed.The outer ring is a perfect ring resonator and the inner one is split ring with a narrow gap inserting in the ring.The transmission characteristics under different geometric parameters are analyzed by numerical and analytical methods.Simulation results show that when the width of the split is θ = 5 and the position of the split is φ = 45,a significant PIA phenomenon occurs at the wavelength of 674 nm.Based on this unique property,the application of the structure in the field of refractive index sensor was studied at first.The results show that the sensitivity exceeds 600/RIU and the maximum figure of merit(FOM)is about 700.Secondly,the characteristics of fast-and slow-light are studied.Calculation showed that the optical delay time at the PIA transmission dip is about-0.081 ps,which means the larger abnormal dispersion and the fast-light effect.The optical delay time at the transmission peaks on both sides of PIA transmission dip is about 0.045 ps and 0.043 ps respectively,which means the larger normal dispersion and the slow-light effect.(2)An MIM-type SPW composed of a U-shaped cavity and a rectangular cavity was designed.At the same time,the influences of changing geometric parameters on the transmission characteristics were also studied.Due to the destructive interference between the different transmission paths,the PIT effect can be achieved.The adjusting of PIT effects can be achieved by changing the position and size of the rectangular cavity.The double PIT effect can be achieved by increasing the number of rectangular cavities.In addition,the characteristics of refractive index sensing and the effects of slow-and fast-light supported by the proposed structure were also studied.(3)An MIM-type compound SPW is reported,which possesses the transmission property of PIT and exhibits the potential application of refractive index sensing.The waveguide structure consists of an MIM-type bus waveguide,a horizontally placed asymmetric H-type resonator(AHR),and a circular ring resonator(CRR).Due to the destructive interference between the two different transmission paths,PIT effect can be observed in the transmission spectrum.The simulation results show that the proposed waveguide structure has potential application prospects in the area of temperature and refractive index sensing with higher sensitivity and better figure of merit. |
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