Z-掃描量測碲化鋅之三階非線性效應

Abstract

利用飛秒超短脈衝鈦藍寶石雷射（波長800nm）從事變化強度Z-掃瞄量測技術研究碲化鋅(Eg=2.26eV)。發現此樣品的非線性折射係數n2約為1.373x10-13cm2/W ，跟一般理論預測在入射光子能量是介於一半能隙和能隙之間時，n2<0，似乎不吻合。認為是自旋-軌道偶合能帶能量接近雙光子共振。非線性吸收係數的增強猜測可能是THz電磁輻射的產生導致。

By using a femtosecond Ti:sapphire laser (wavelength = 800nm) as z-scan source, we have studied intensity dependent nonlinear refractive index of the ZnTe. The positive nonlinear refractive index is observed for n2=1.373x10-13cm2/W. In regime，general theory shows that c(3)<0. The discrepancy of our result with theory is explained by two photon near-resonant to spin-orbital split band transition. Larger nonlinear absorption may be enhanced by THz generation.