Fig. 1. Test principle of transmission terahertz time-domain spectral system

Fig. 2. Schematics of instrument for laser induced damage test

Fig. 3. Damage images of fused silica induced under different laser energies. (a) 50 mJ; (b) 60 mJ; (c) 70 mJ; (d) 80 mJ

Fig. 4. Schematics of sample test models. (a) Terahertz wave propagates in air; (b) terahertz wave penetrates into the sample

Fig. 5. Time-domain waveforms when tested. (a) Reference signal without the sample; (b) waveforms of undamaged and damaged areas in fused silica under different laser energies

Fig. 6. Amplitude spectra of reference signal, undamaged area and damaged areas in fused silica under different laser energies

Fig. 7. Transmission spectra of undamaged and damaged areas in fused silica under different laser energies

Fig. 8. Refractive index curves of undamaged and damaged areas in fused silica under different laser energies

Fig. 9. Absorbance curves of undamaged and damaged areas in fused silica under different laser energies