We analyzed the caramel lens in a terahertz pulsed imaging (TPI) setup shown in Fig. 3, using a 780-nm femtosecond laser source (Menlo Systems, 82 fs, 100 MHz) in a pump-probe detection scheme. A parabolic lens (, Menlo) collimates a terahertz beam emerging from the terahertz PCA ( dipole with the emission peak at 0.2 THz, and the maximum frequency of 1.5 THz), biased and chopped by an electronic circuit.14 To characterize the quality of the collimated beam, we blocked the THz beam after the TPX lens at different positions in two axes as in the widely used knife-edge method. The beam waist () measured in the direction was 13.1 mm after the collimating lens, 14.2 mm between the two lenses spaced by 10 cm, and 12.3 mm at the caramel lens entrance. In the -axis scan, the obtained values were 14.5, 13.3, and 13.8 mm, respectively. Notably, because of the significant diffraction, this method provides only a rough estimate of the terahertz beam parameters.