Thermally tunable broadband metamaterial absorbers based on ionic liquids.

In this paper, we propose an interesting thermally tunable broadband metamaterial absorber based on ionic liquids at the microwave band, which has distinct modulation characteristics in different frequency bands. Numerical simulation results show that the absorption decreases with the increase of temperature in the low-frequency band from 2-10GHz, which decreases to 60% at 100 °C. Meanwhile, the absorption increases with the increase in temperature in the high-frequency band from 25GHz to 48GHz. In addition, the absorber still has good broadband absorption without the metal substrate, and the absorption reaches more than 80% in the frequency band of 13.96-34.10GHz. As an all-dielectric metamaterial absorber, its absorption increases with the increase in temperature, which reaches more than 90% in the range of 20.44-50GHz at 100 °C. At last, the designed metamaterial absorbers have been fabricated based on ionic liquids, and experimental results are presented to demonstrate the validity of the proposed structure. Furthermore, the simple design and wide frequency tuning range of the absorbers can promise a great potential application in sensors, detection, and frequency-selective thermal emitters.