Fig. 1

a Schematic of the metamaterial coupled detector. b Three-dimensional diagram for one metamaterial building block. Inset: self-consistently calculated conduction band structure of one period of the QCD. Starting with quantum well A from left to right, the layer thicknesses in angstroms are 105/52/39/47/50/48/68/44, where In_0.53Ga_0.47As wells are in bold, In_0.52Al_0.48As barriers are in roman, and the underlined active well A is Si-doped (\( n \) = 4.5 × 10¹⁷ cm⁻³)