The Design Of Terahertz Bilayer Metamaterial Filters Based On Guide Mode Resonance

Metamaterials(MM)are a class of artificial composite materials that are periodic arranged in subwavelength structures and are of great research value because they exhibit many unique properties that natural materials do not have.The development of metamaterials is closely related to the advancement of terahertz technology.With the development of terahertz launchers and detectors in recent years,terahertz technology has been developed unprecedentedly.The development of terahertz technology and its applications have also stimulates the need of the basic devices.Terahertz filters are no exception as one of the most practical functional devices.Filters can filter out unwanted noise or clutter that in the application environment,which is very important to improve the performance of the system.The THz filter based on guided-mode resonance studied in this paper takes advantage of the narrow bandwidth,symmetrical peak shape and high transmittance of guided mode resonance.This type of filter can be designed as tunable,multiband and other devices with different functions for different application requirements.The specific contents are as follows:(1)A guided-mode resonance band-pass filter based on metallic one-dimensional grating is studied.We analyze the filter from the principle,including the relationship between structural parameters and the tunability.In order to improve the amplitude of the resonance peak and sidelobe suppression ratio in the passband center,we further design a filter in bilayer one-dimensional grating structure.After analysis and comparison,the sidelobe suppression ratio of the filter with bilayer structure can be increased by 50% to 100% with keeping the amplitude of the single layer grating in same level.(2)A two-dimensional metallic metamaterial grating filter based on the slab waveguide was analyzed.This filter can excite the fundamental guided modes both in x and y directions of metamaterial grating simultaneously.Moreover,we design a novel multiband guided-mode resonance filter based on bilayer asymmetric metamaterial gratings.This filter is obtained by breaking the symmetry of the upper and lower structures,and leads to the splitting of the two fundamental guided modes.Then we achieve the filter with four band within the range 1.4 ~ 2.0THz.In addition,three-band and two-band filters can obtained by changing the relative position between the double layer gratings.(3)To perform experimental verification we design a cross-structure metamaterial guided mode resonant filter.We fabricated the metamaterial waveguide device using laser exposure and wet etching.Then we compared the simulation data with the results measured by spectrometer.These two results fit well.