Design Of Tunable Terahertz Filter Based On Electrostatically Actuated Reconfigurable Metamaterials

The terahertz(THz)filter can be used to remove unwanted frequencies and noise.Metamaterials are artificial composite materials and structures which with special electromagnetic response characteristics.However,most commercialized filters can only select special frequencies,and the amplitude and central frequencies of the passbands or stopbands cannot be dynamically modulated,which greatly limited their applications.Therefore,the THz filters with tunable amplitude or central frequency are urgently needed at the present.In this dissertation,we mainly study the tunable filters based on electrostatically actuated reconfigurable metamaterial,and the specific contents are as follow.(1)Studied the electrostatic comb actuator based on microelectromechanical systems(MEMS).In this section,we mainly studied the influence of the structural parameters on the maximum displacement of the actuator.The electrostatic actuators connected with a movable frame through springs.When a DC voltage is applied to the electrostatic comb actuators,the electrostatic comb actuators and the movable frame can simultenousely move in the same direction.When a 30 V DC voltage is applied,the maximum displacement of the electrostatic comb actuatorcan reaches to 3 microns.(2)Studied the tunable bandstop filter based on MEMS electrostatically actuated reconfigurable metamaterials.In this section,we designed a tunable THz filter which consists of a trapezoidal ring structure and a cross bar.When the space between two structures is 3 microns,the center frequency of the stopband located at 1.25 THz.When two structures contacted each other,the center frequency of the stopband located at 0.98 THz,and thus the modulation depth of the stopband center frequency reached 21.6%.The mechanism of filter and the influence of structure parameters on the filter characteristics are studied using a finite integral time domain(FIDT)method.(3)Studied the tunable bandpass filter based on MEMS electrostatically actuated reconfigurable metamaterials.The filter consists of a movable crossbar and two split ring resonators.When the movable bar located at the center of the two split ring resonators,the filter has two passbands locating at frequencies of 0.65 THz and 0.95 THz,respectively.When the movable bar approaches the lower open ring,the high frequency passband will gradually decrease until it reaches to zero.The mechanism of the filter and the influence ofthe structure parameters on the characteristics of the filter are studied using the FIDT method.The sample was fabricated by a Silicon-On-Isolator(SOI)bulk micromachining process,and characterized using a THz time domain spectrum system.The result shows that the amplitude of high frequency passband achived to about zero at U=120V.The simulation shows good agreement with the experiment.