The absorption coefficient of magnesium-doped near-stoichiometric lithium niobate crystal is measured by terahertz time-domain spectroscopy in a frequency range of 0.2 THz–0.9 THz at room temperature.The absorption coefficient is modulated by external optical pump fields.Experimental results show that the absorption coefficient of near-SLN:Mg crystal is approximately in a range of 22 cm-1–35 cm-1in a frequency range of 0.2 THz–0.9 THz and tunable up to nearly15%.Further theoretical analysis reveals that the variation of absorption coefficient is related to the number of light-induced carriers,domain reversal process,and OH-absorption in this crystal.
