Fig. 1. Layout of the terahertz imaging experiment. SAS, saturated absorption spectroscopy; EIT, electromagnetically induced transparency; HR mirror, high reflective mirror.

Fig. 2. Fluorescence images acquired pre- and post-installation of a terahertz polarizer. (a) The fluorescence image before positioning a terahertz polarizer. (b) The fluorescence image after positioning a terahertz polarizer.

Fig. 3. Schematic illustration of the pipeline of the untrained neural network. (a) Details for the U-shaped network structure. (b) Schematic diagram of the physics-enhanced deep neural network.

Fig. 4. Simulation for the resolution test card imaging. (a) Binarization diagram of the resolution test card. (b1) Intensity image of the resolution test card at 9 mm distance. (b2) Intensity image of the resolution test card at 13 mm distance.

Fig. 5. Simulation for fluorescence image processing using untrained neural networks. (a1), (b1) represent the amplitude image and the phase image predicted by the neural network with n = 1, respectively. (a2), (b2) represent the amplitude image and the phase image predicted by the neural network with n = 2, respectively.

Fig. 6. Schematic diagram of the imaging experiment.

Fig. 7. Resolution test card fluorescence imaging experiment. (a)–(f) denote the imaging distances of 2.5, 4.5, 6.5, 8.5, 10.5, and 12.5 mm, respectively.

Fig. 8. Resolution test card fluorescence image processing results. (a)–(c) represent the amplitude images reconstructed from n = 2, n = 4, and n = 6 pictures by our algorithm, respectively.

Fig. 9. Phenomenon of THz waves reflecting within the atom vapor cell. (a) Fluorescence image of the metallic disc. (b) Fluorescence image without THz irradiation.