Design of tunable terahertz bandstop filter based on electrostatically actuated reconfigurable metamaterials

A tunable terahertz (THz) bandstop filter based on electrostatically actuated microelectromechanical systems (MEMS) reconfigurable metamaterials is presented. The central part of the filter is a periodic array structure, and each unit cell consists of a movable bar and a fixed inverted trapezoidal ring. When direct current (DC) voltage is applied to actuate the electrostatic comb actuators symmetrically positioned on both sides, the movable frame and all movable bars can move in-plane. This will reconfigure the unit cell of the filter, and thus change its resonance frequency. Finite integration time domain (FITD) method is used to study the working mechanism and the influence of structure parameters. The results show that the performance of the filter strongly depends on the distance between the trapezoidal ring and the cross bar, the width of inverted trapezoidal ring and the basic angle of trapezoidal ring. A finite element analysis (FEA) method is introduced to study the electromechanical performance of the actuator, and a displacement of 3 µm is achieved at DC 30 V. The corresponding modulation of central frequency is about 24%. The potential applications of this tunable THz bandstop filter are THz communication, THz beam control and frequency selective detection.