Research On The Key Technologies Of Sub-wavelength Optical Devices Based On Surface Plasmon Polaritons

Modern society is with information data as its resources,information industry as its pillar,and information technology as its foundation.With the rapid development,the requirements of high speed,miniaturization,and large capacity of components are very strict.The inherent delays,power consumption,and bandwidth of traditional electronic devices have limited their develop speed.In contrast,optical devices have faster transmission,larger communication bandwidths,and smaller sizes,which have become the important technical supports and guarantees for the development of new-generation information technology.However,optical devices also have problems and challenges.Due to the diffraction limits,the size of traditional optical devices can never break through the sub-wavelength order,and the integration cannot be further improved.In recent years,with the development of sub-wavelength electromagnetics,scholars have discovered that there is a special electromagnetic wave called surface plasmon polaritons(SPPs)at the interface between metal and insulator.It is formed by the interaction between free electrons and photons,and it is concentrated to the metal-insulator surface.SPPs waves propagate along the metal surface and attenuate exponentially in the direction perpendicular to the surface of metal.They have concentrated characteristics and can break the limit of diffraction limits to control photons in the sub-wavelength scale.Therefore,sub-wavelength optical devices based on SPPs to achieve different functions have emerged endlessly.In order to realize the control of optical devices based on SPPs,the traditional method is to directly change the geometric parameters of the device structure.However,this method is difficult to implement after the device is manufactured,the changes caused of structure are irreversible,and the precise control is difficult to achieve.Aiming at this problem,my research proposes novel optical devices at the sub-wavelength scale such as optical logic device,delay lines,and power splitter.Their performance can be adjusted without changing the structural geometric parameters.The specific research contents are as follows:1.A novel and compact logic device based on plasmon-induced transparency(PIT)is investigated.This device consists of a pair of hexagonal ring resonators coupled with two parallel metal-insulator-metal(MIM)waveguides and can implement the function of logical operations XOR and XNOR simultaneously.According to the temporal coupled-mode theory,the appropriate detuning between the resonance wavelengths of two resonators act as the key factor to achieve the PIT.The finite-difference time-domain(FDTD)simulation results reveal that the structural parameters have an important influence on the transmission characteristic,such as the refractive index of insulator in resonators.Using thermo-optic effect,electro-optic effect,and pump light to change the refractive index,logic states 1 and 0 which are represented by the high and low levels of the optical power can be achieved at the through and drop port.So the proposed structure can implement the logical operations XOR and XNOR simultaneously.2.A tunable optical delay ilne based on optical driven rotating is achieved in a novel and compact plasmonic system which consists of dual hexagonal resonators with rotatable rectangular bar embedded in resonators.By rotating the embedded bar to different angles,slow light effect can realize in different wavelengths.The numerical simulation results of FDTD method are used to verify the theoretical model.They reveal that tunability in transparency peak wavelength,transmission,and optical delay are obtained when the angle of embedded bars are changed.In addition,the influences of other structural parameters on transmission and optical delay are analyzed in detail,they can provide references for structural optimization.3.A novel plasmonic power splitter with variable transmissions and selectable channels is presented using hexagonal resonator with inserted silver ellipse.Rotating the silver ellipse to different angles will break the symmetry of structure and change the propagation path of SPPs.The FDTD simulation results reveal that the variable transmissions and selectable channels are achieved by rotating the inserted ellipse.Besides elliptical core,other components such as rectangular and triangular core are investigated in detail.Comparing the simulation results of three different structures,it is found that the power splitter with elliptical core has larger transmission and it is easier to adjust the transmission according to the requirements since its error range of rotation angle is larger than the others.The proposed device can realize the dynamic control of optical signals with the highly integrated chip.The above optical devices will play an important role in many application scenarios such as optical computing,optical storage,and optical networks on-chip.Compared with traditional methods,the proposed performance adjustment method is easier to implement.It can ensure the integrity of the device,and provides a novel idea for the realization of new sub-wavelength optical devices.