Highly flexible wide angle of incidence terahertz metamaterial absorber: Design, fabrication, and characterization

We present the design, fabrication, and characterization of a metamaterial absorber which is resonant at terahertz frequencies. We experimentally demonstrate an absorptivity of 0.97 at 1.6 THz. Importantly, our absorber is only $16\mu \text{m}$ thick, resulting in a highly flexible material that, further, operates over a wide range of angles of incidence for both transverse electric and transverse magnetic radiation.

Figure 1

(Color online) Terahertz metamaterial absorber consisting of two metallic layers and two dielectric layers. (a) Electric SRR: unit-cell $a$: $36\mu \text{m}$, SRR side length $b$: $25.9\mu \text{m}$, capacitor length $c$: $10.8\mu \text{m}$, capacitor gap $g$: $1.4\mu \text{m}$, and linewidth $w$: $3\mu \text{m}$. (b) Perspective view of the absorber. Each dielectric layer, $t_1$ and $t_2$, is $8\mu \text{m}$ thick. (c) Photograph of a portion of the experimentally realized absorber.

Figure 2

(Color online) Simulations of the metamaterial absorber showing the absorptivity as a function of frequency at various angles of incidence for (a) TE and (b) TM incident radiation. The insets depict the orientation of the fields with respect to the SRR. The labels for the curves show the angle of incidence and the corresponding peak absorptivity.

Figure 3

(Color online) The simulated absorption (for normal incidence) out to 3.5 THz revealing an additional absorption. The middle panel shows the calculated surface current density for the low-frequency absorption, while the lower panel shows the calculated surface current density for the higher-frequency resonance. The red dashed curve shows the absorption with the capacitor shorted highlighting the importance of the in-plane electric response in determining the low-frequency absorption.

Figure 4

(Color online) Experimentally measured absorption as a function of frequency for (a) TE and (b) TM radiation at $30°$, $45°$, and $60°$ angles of incidence.