Z-掃瞄量測硒化鋅微晶玻璃薄膜之三階及五階非線性效應

Abstract

利用飛秒超短脈衝鈦藍寶石雷射（波長790nm）從事變化強度Z-掃瞄量測技術研究硒化鋅微晶玻璃薄膜，我們發現此樣品除了非線性折射係數n2約為+1.28x10-7 ~ +3.84x10-7(esu)，比ZnSe塊材在光源波長532nm量測到的n2約為-4.4×10-11(esu)大了許多之外，並無非線性吸收之現象。由螢光和穿透光譜得到由量子侷限的效應造成能隙的藍位移。非線性折射係數的增強可能是由於量子侷限效應和雙光子接近共振所致。此外，非線性折射率隨光強的飽和現象可以用二階史塔克效應來解釋。

By using a femtosecond Ti:sapphire laser (wavelength = 790nm) as z-scan source, we have studied intensity dependent nonlinear refractive index of the ZnSe doped glass thin films grown by pulsed laser deposition. Besides, the measured nonlinear refractive coefficient n2 is between +1.28 ~ +3.84x10-7 (esu), which is much larger than that of bulk ZnSe which is -4.4×10-11 (esu) measured at 532nm, there is no evidence of nonlinear absorption. From the photoluminescence and absorption spectra, we found blue shift of bandgap due to the quantum confinement effect. Enhancement of the nonlinear refractive index may be a result of quantum confinement effect and two-photon near resonance. Furthermore, the intensity induced saturation of nonlinear refractive index can be explained by quadratic Stark effect.