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Reconfigurable THz metamaterial based on microelectromechanical cantilever switches with a dimpled tip

Ying Huang, Taiyu Okatani, Naoki Inomata, and Yoshiaki Kanamori

Open Access Open Access

Abstract

We numerically and experimentally proposed a reconfigurable THz metamaterial (MM) by employing microelectromechanical cantilevers into a ladder-shaped MM (LS-MM). A fixed-free cantilever array with a dimpled tip behaved as Ohmic switches to reshape the LS-MM so as to actively regular the transmission response of THz waves. The cantilever tip was designed to be a concave dimple to improve the operational life without sacrificing the mechanical resonant frequency (fmr), and a fmr of 635 kHz was demonstrated. The device actively achieved a 115-GHz change in transmittance resonant frequency and a 1.82-rad difference in transmission phase shift, which can practically benefit advancing THz applications such as fast THz imaging and 6 G communications.

© 2023 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

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Supplementary Material (2)

NameDescription
Supplement 1       Measured optical constant of a bare SiO2 that used for the simulation model
Visualization 1       A video that shows the dynamic vibration of the fabricated cantilevers.

Data availability

Data underlying the results presented in this paper are not publicly available at this time but may be obtained from the authors upon reasonable request.

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Figures (10)
Fig. 1.
Fig. 1. Schematics of the proposed MEMS-LS-MM. (a) Geometric structure of the array and a one-unit cell of the device. (b) Charge distribution (left-hand side) and the cross-sectional view (right-hand side) of the one-unit cell at different states.

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Fig. 2.
Fig. 2. Calculated results of the device at the off- and on-states. (a) Transmittance. (b) Transmission phase shift. Real parts of the electric fields in y-component of the device at the (c) off- and (d) on-state both for an incidence of the on-state-resonance of 0.67 THz.

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Fig. 3.
Fig. 3. Calculated deformation of the cantilever during vibration. (a) The geometry of the cantilever at the initial state in the calculation model. (b) A snapshot of the displacement field of the cantilever, where the hollow black frame shows the initial position of the cantilever. (c) The normalized displacement of the edge of the dimpled tip, where d is the distance from the wall-free side tip as marked in (a).

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Fig. 4.
Fig. 4. Fabrication flow of the device.

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Fig. 5.
Fig. 5. SEM images of the fabricated device. Zoom-in view of (a) the array structure and (b) one-unit cantilever.

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Fig. 6.
Fig. 6. Measured velocity (above) and the computed displacement (below) of the cantilever with respect to the voltage ramp.

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Fig. 7.
Fig. 7. Measured mechanic response of the cantilever actuator. The pink dots show the measured FFT signal of the magnitude of the vibration velocity. △fm is a −3 dB bandwidth. Inset shows the laser spot position in the cantilever.

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Fig. 8.
Fig. 8. Schematic of the transmission measurement setup.

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Fig. 9.
Fig. 9. Measured active transmittance (above) and transmission phase shift (below) of the device at the rest (0 V) and actuated (165 V) states.

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Fig. 10.
Fig. 10. Calculated for as a function of δ.

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Tables (1)

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Table 1. Designed and fabricated dimensions of the device.

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