Fig. 1. Experimental setup and optical arrangement of terahertz time-domain spectroscopy system

Fig. 2. Digital photograph of six kinds of pigment tablet samples

Fig. 3. Terahertz time domain waveform diagram of six pigments

Fig. 4. Terahertz frequency domain waveform diagram of six pigments

Fig. 5. Transmission spectra of six pigments

Fig. 6. Refractive index spectra of six pigments

Fig. 7. Absorption spectra of six pigments

Fig. 8. Refractive index spectra of garcinia and orpiment

Fig. 9. Absorption spectra of garcinia and orpiment

Fig. 10. Refractive index spectra of laterite and sinopis

Fig. 11. Absorption spectra of laterite and sinopis