Liquid Crystal-modulated Tunable Filter Based On Surface Plasmon

Since the 21st century,the emerging discipline of surface plasmon has set off a research boom in the field of plasmonic nanostructured materials.The development of traditional electronic devices has encountered bottlenecks,and its calculation speed is difficult to improve qualitatively.Surface plasma?SPs?is an electromagnetic mode that propagates at the interface between metal and dielectric.Various sub-wavelength nano-lights based on SPs Waveguide devices can break through the limitations of the diffraction limit and bind the electromagnetic field to an order of magnitude well below the wavelength of the incident light.Moreover,the plasmonic nanostructured materials have the advantages of small size,suitable for integration,breakthrough of optical diffraction limit,etc.,and have great application prospects in the fields of solar energy,sensors,filters and optical couplers.One major drawback of most plasmonic devices is that the fabricated nanostructures serve as passive devices providing consistent output given an input,which greatly limits their application,making dynamic tuning difficult,which greatly limits their application.In this paper,a tunable filter based on plasmon-induced transparency and cavity mode coupling is proposed.The main research contents are as follows:1?A nanorod-ITO Glass-Au film?NIGAF?structure consisting of Au nanorod dimer PIT array instead of the Au film on the top layer of the FP cavity.It is well established that this system can achieve double absorptive peaks resulting from the strong plasmonic coupling between the plasmon induced transparency effect of the nanorod array and the cavity mode of the Au micro-cavity structure in the near-infrared band.And the reflection spectrum,the electric field and magnetic field distribution maps of the NIGAF structure are analyzed.2?The electro-optic effect of the liquid crystal is studied,and a tunable filter model is established.The filter is able to filter two peaks with a reflection coefficient of less than 5%.By using the characteristics of the liquid crystal refractive index to be easily controlled,the effective refractive index of the liquid crystal is controlled by applied voltage,thereby realizing dynamic tunability of the filter.As the voltage increases,the effective refractive index of the liquid crystal increases,and the two modes have a significant red shift.When the voltage is from 0V to 8V,the tunable range is 160nm,and the polynomial fitting curve of the voltage and the tuning wavelength range is obtained.3?Various factors of the tunable characteristics of the filter are analyzed.We have further investigated that the resonance wavelength and the linewidth of double absorptive peaks can be flexibly tailored by controlling the cavity length,the thickness of SiO₂,size of period,the angle of incidence and size of the nanorod dimer.Finally,since the liquid crystal may change the polarization direction of the incident light,a symmetric NIGAF structure filter is proposed to reduce the influence of polarization on the simulation results.