Fig. 1. Structure parameters of plano-convex lens

Fig. 2. Size of focused spot on single lens

Fig. 3. Terahertz beam shaping optical system

Fig. 4. Size of focused spot on sample surface

Fig. 5. Terahertz spectrum test

Fig. 6. Terahertz time-domain and frequency-domain signals

Fig. 7. Frequency-domain curves about refractive index and absorption coefficient of moxifloxacin hydrochloride and levofloxacin