Thermally-Electrically Tunable Coherent Terahertz Perfect Absorber

Herein, we present an electrically and thermally bi-tunable narrow-band terahertz wave (THz) perfect absorber scheme. Dual narrow-band spectrum with the maximal absorption of 99.9% and 98.2% at 0.415 THz (
$f_{1}$
) and 1.231 THz (
$f_{2}$
) is achieved respectively. Moreover, it is interesting to note that the resonant absorption frequencies can be feasibly shifted in a wide range (
$f_{1}$
: 0.373~0.487 THz,
$f_{2}$
: 1.108~1.443 THz) when the surrounding temperature varies in a limited region. On this basis, the temperature sensitivity of the two absorption peaks is 0.76 and 2.23 GHz/K, respectively. Otherwise, the peak absorptivities can be further adjusted in a large range (64.7% to 99.9%) for
$f_{1}$
and (57.6% to 99.8%) for
$f_{2}$
by adjusting the Fermi energy. Impedance matching theory and multiple interference theory are used to further explain the absorption mechanism. Finally, we study the nanosecond photothermal effects, calculate the maximum and average transient temperatures of thermally sensitive materials, and analyze the causes of the temperature rise. These findings on the achievement of simultaneously adjusting the frequency and intensity for the absorbers via the electrical and thermal operations hold potential prospects in artificially tunable optoelectronic devices.