Figure 1.

(a) Configuration of the theoretical model. The metamaterial absorber (MA) slab in deep sub-wavelength thickness $d\ll \lambda$ is located between the background medium and rigid wall. The reflected waves exhibit π phase jump at the front surface and zero reflection phase at the rear surface, respectively. (b) Map of theoretical reflectance R in dependence on the real and imaginary parts of E_1/E₀ at slab thickness d = λ/30, where E₁ and E₀ are the effective bulk modulus of MA slab and background medium, respectively. (c) Reflectance R for E_eff/E₀ = 0.041i, 0.209i and 0.785i at different λ/d with λ fixed. (d) Reflectance R in dependence on the imaginary part of E₁/E₀ and λ/d with λ fixed. The simulations confirm the analytical predictions.