非線性光學在目前應用的範圍非常廣泛，包括電光調變、頻率轉換、光通訊應用之色散補償等。一般具二階非線性光學性質的物質如Quartz、LiNbO3、LiTaO3等等，都是晶體結構或是化學合成的高分子化合物。1991年R.A. Myers等發現將熔融石英平面基板加熱，並施加高電壓(熱極化法)，成功地使中心對稱結構的熔融石英基板產生恆常性的二階非線性光學特性，使得價格便宜之熔融石英獲得更廣泛的應用。
本論文主要在探討熱極化熔融石英產生的二階非線性光學特性隨時間衰減之現象，目前其他研究熱極化之學者都尚未提出有關熱極化空白熔融石英後的衰減現象。用以實驗的熔融石英分別為屬於Type I製程的GE124與Type II製程的KV。GE124在大氣環境熱極化所得之二階非線性特性幾乎不衰減，但在真空環境熱極化後，會有明顯衰減現象。KV在大氣與真空環境熱極化後都有衰減現象，若在熱極化降溫後持續加高電壓一段時間，可以減緩衰減，而且熱極化後之樣品保存在低濕度的環境中，可以有效抑止衰減。衰減過程中二階非線性特性衰減，但非線性分佈深度不變。
對於大氣與真空環境下熱極化之比較，實驗結果為兩者所產生之二階非線性特性與非線性分佈深度大致相同。

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