Fig. 4: Optical response of asymmetric structure NbFeTe₂-based photodetector at room temperature.

(asymmetric split-ring devices) a The designed sub-wavelength structure of reordered device, and the channel part is outlined by a white dashed line in along with (b) the simulated THz-field profile. The inset depicts the coupling strength distribution at the position of the yellow dashed line. c The non-uniform distribution of the localized THz field in the channel generates a potential difference, supplying carriers with the necessary energy to escape from their localized states. d The photocurrent across various frequency bands. e Optical response waveforms at different frequencies captured by an oscilloscope. f The zero-bias waveform demonstrates a response time of 7.7 μs and a recovery time of 13.7 μs. g The bias voltage dependent responsivity, showing linear growth at different frequencies. h The comparison of responsivity between symmetric bow-tie devices and asymmetric split-ring devices. i Scanned THz imaging results clearly reveal the profile of metallic fingers at 0.29 THz.