Reconfigurable Transmission Regulation Based On Spoof Surface Plasmon Polaritons

The next-generation inter-chip communication requires ultra-fast and ultra-compact interconnections to achieve reliable and high signal integrity data transmission.The concept of spoof surface plasmon polaritons(SSPPs)makes it possible to achieve this goal.Surface plasmon polaritons(SPPs)can confine electromagnetic fields in a deep subwavelength volume,resulting in numerous applications at optical frequencies.The concept of SPPs is transferred from optical frequency to microwave and terahertz frequency via the metal periodic drilling.However,due to its blocky structure,it is difficult to be compatible with integrated circuits and communication systems.To solve this problem,an ultra-thin conformal SSPP waveguide is proposed by Cui and coworkers.SSPPs not only inherit the advantages of optical SPPs with strong filed confinement but also have their own characteristics such as low ohmic loss and flexible regulation of dispersion behaviors.Compared with traditional microstrip lines,SSPP waveguides can be packaged in a highly dense way in the circuit and effectively suppress the crosstalk between parallel waveguides.In recent years,due to the merits of SSPPs,a variety of SSPP-based devices have been verified by theoretical analysis and experimental measurements.This thesis systematically studies the transmission regulation mechanism of SSPPs.Thanks to the strong field confinement and controllable dispersion behaviors,the reconfigurable multifunctional devices and the enhancement of the nonlinear conversion process are proposed and experimentally demonstrated.The main contents and innovations of the thesis are summarized as follows.1)An efficient method to suppress crosstalk based on the mode mismatch between SSPP transmission line and traditional microstrip line.Since SSPP transmission line and traditional microstrip line support the transverse magnetic wave and quasi-transverse electromagnetic wave,respectively,the corresponding electromagnetic wave is hardly coupled between two kinds of waveguides.SSPP waveguides with different structural parameters are introduced into the microstrip circuit to suppress the crosstalk coupling under strong and weak coupling cases.High transmission performance and low crosstalk promote plasmonic metamaterials to provide great application potential in miniaturized large-scale integrated circuits and communication systems.2)Reconfigurable multifunctional devices based on SSPP are proposed.By changing the capacitance of the varactor loaded on two mirrors’ symmetrical SSPP unit structure,the flexible dispersion behaviors can be realized.Then,the signal energy distribution of SSPP between waveguides can be manipulated freely via switching the bias voltage applied to the varactors so as to realize the reconfigurable multifunctional couper.In addition,when the active chips are integrated into a mixing circuit composed of SSPP waveguide and substrate integrated waveguide,by adjusting the bias voltages of the chips on SSPP waveguides of the upper and lower branches the reconfigurable power device is realized.3)Reprogrammable SSPP neural network in an ultra-thin and compact plasmonic metamaterial platform is proposed and realized.In such a multi-port architecture,the real-time control and feedback methods of field programmable logic gate array,detector,and amplifier chips are established.Then,we use multiple neurons with 16 independently adjustable weight coefficients to design and construct a partially-connected neural network,which achieves a higher prediction accuracy than the same scale fully connected network.The concept of SSPP neural network paves a way for all-optical artificial intelligence devices,which may stimulate the application potential in fields such as large-scale optical computing and communication systems.4)Dynamic controls of second-harmonic generation in both forward and backward modes using reconfigurable plasmonic waveguide are verified.To obtain the nonlinearity and tunability,we introduce the varactors into the specially designed SSPP waveguide.By switching the bias voltage of the varactor,the forward and backward phase-matching conditions between the fundamental and second-harmonic waves are realized.Furthermore,the reconfigurable second-harmonic generation in a certain frequency band can be achieved on an ultra-thin plasmonic metamaterial platform,5)A reconfigurable parametric amplifier based on SSPP is proposed.The theoretical analysis of parametric amplification with three-wave mixing is derived by Maxwell equations to predict the amplified signal gain of SSPP waveguide.By manipulating the dispersion behaviors of SSPP,different phase-matching conditions are satisfied,allowing the multi-frequency parametric amplified signal via switching the bias voltage applied to the varactor.Moreover,compared with the MOS-based amplifier,the proposed parametric amplifier will not cause phase distortion.6)A non-magnetic non-reciprocal isolator with parametric amplification is proposed.The forward signal generated from the SSPP parametric amplifier is amplified.The amplified forward signal is coupled to the passive SSPP waveguide via the spoof localized SPP resonator,whereas the transmission from the backward direction is suppressed.Therefore,the magnetic-free isolator can be achieved on an ultra-thin plasmonic metamaterial platform.Additionally,due to the arbitrary controllability of SSPP dispersion behaviors,multi-frequency isolation is verified by switching the bias voltage applied to the varactor.