Fig. 1. Experimental principle, device, and performance of the terahertz optoacoustic detector. (a) Principle of the terahertz optoacoustic (THz-OA) array detector. (b) Schematic system for the terahertz array photoacoustic detector.

Fig. 2. (a) Signal amplitude from the terahertz optoacoustic detector as a function of terahertz radiation energy as determined by the Golay cell. (b) THz-OA signals in the time domain. (c) Signal intensity of PDMS doped with the CNT. (d) Relationship between the optoacoustic signal intensity of other materials and their doped CNT concentration. (e) Relationship between the optoacoustic signal intensities of EMMIm and the ambient temperature. (f) Frequency distribution of optoacoustic signals generated by EMMIm materials of different diameter sizes.

Fig. 3. Imaging results of terahertz spots under different sizes of optoacoustic conversion materials. (a) Terahertz spots captured by different detectors under different sample conditions at the focal point. (b) Light spot curves of different intermediate frequency (IF) probes at y = 0 under the condition of the 0.5 mm sample [corresponding to the horizontal dotted line in (a)] and light spot curves of 1 MHz IF probes at x = 0 [corresponding to the longitudinal dotted line in (a)] under different sample sizes. (c) Physical and dimensional drawings of cross metal samples. (d) Scanning imaging of the terahertz detector in the near field behind a transmitting sample. (e) The ESF and the LSF calculated from (d).

Fig. 4. Spot scanning results of the terahertz propagation process in three-dimensional space. (a) Three-dimensional scanning imaging effect of a terahertz beam during transmission near the focal point. (b) Imaging results of the spot at 8 positions in (a).

Fig. 5. Imaging results from the terahertz array detector for the terahertz spot. (a) Scanning result of a piezoelectric probe with a crystal size of 0.5 mm × 0.5 mm and an intermediate frequency of 1 MHz. (b) Imaging results of four piezoelectric-based terahertz detectors operating synchronously. (c) Imaging result of a detector with a crystal face size of 0.5 mm × 0.5 mm and an array of 8 × 8. (d) Imaging result of a detector with a crystal face size of 0.3 mm × 0.3 mm and an array of 10 × 10.