Fig. 4: High-frequency anisotropy photocurrent and imaging application.

a Schematic illustration of the polarization-sensitive photocurrent measurement. b Polarization-angle dependence of the photocurrent response along the x, y direction at different bias voltages. The angle of the polarizer rotates clockwise with respect to the polarization orientation of the incident light. The anisotropic ratio is defined as the ratio of the photocurrent response in the y direction to that in the x direction. c Different photocurrent corresponding to two mutual vertical electrodes increase with the bias voltage. Anisotropic photocurrent response of device along two orthogonal crystalline directions with bias added up to ±100 mV. d Optical path diagram based on THz imaging. e–g Photographs of the enclosed blade, copper lettering “THz” and metallic ring, and their raster scanning imaging at 0.3 THz. The objects were clearly revealed in an envelope, which was invisible to the naked eye. The NiTe₂-based detector was biased at 10 mV during imaging experiments.