本論文主要研究添加鈦酸鋇奈米粒子於摻雜染料向列型液晶(DDLC)之隨機雷射，藉由外加電場調控與溫度調控以及不同波長光波調控下，探討隨機雷射強度受調控的機制與特性。由實驗結果得知，隨機雷射是由液晶盒內奈米粒子的多重散射所產生，且可藉由外加電壓的大小與控制樣品溫度以及調控UV光(365nm)與綠光(532nm)照射樣品時間共三種方式來調控隨機雷射輸出能量強弱，以下分別描述三種調控機制：
(一)利用外加電壓改變正型液晶的排列方向由水平排向轉為垂直排向，藉此帶動雷射染料跟著旋轉，因此雷射染料的吸收及螢光皆由大變小，使得雷射輸出能量下降。
(二)溫度上升時液晶排列逐漸趨向混亂導致破壞性散射增加，此情況會降低奈米粒子在液晶內的多重散射效果，造成隨機雷射強度下降。當溫度超過相變點液晶呈現透明清澈態，液晶破壞性散射消失，此時ㄧ強隨機雷射將再次出現。
(三)依序曝照UV光與綠光於偶氮染料添加奈米粒子之DDLC樣品內可全光調控隨機雷射輸出。曝照UV(綠)光可使偶氮染料同素異構化由棒狀的trans態變為彎曲狀的cis態(由彎曲cis態回復棒狀的trans態)來增加(減少)液晶擾動引致的破壞性散射，藉此可降低(增加)奈米粒子在液晶中之多重散射效果，進而控制隨機雷射強度的降低(增加)。

This thesis investigates electrically, thermally, and all-optically controllable random lasers based on dye-doped liquid crystal (DDLC) films with BaTiO3 nanoparticles. Experiment result show that the random lasing emission is resulted from the multiple-scattering of the nanoparticles in LC host and can be electrically, thermally and all-optically controlled by varying the applied voltage, the cell temperature, and the exposure times of one UV and one green beams, respectively. The mechanisms of the three controllabilities of the random lasers are described as follows:
(1) The orientational changes of the LCs from homogeneous to homeotropic texture in the presence of increasing applied voltage lead to the absorption and thus the fluorensence emission of the laser dyes to decrease, resulting in the decrease of the random lasing emission.
(2) The increasing destructive scattering resulting from the increasing fluctuation of LCs at increasing temperature can decrease the multiple-scattering effect of the nanoparticles in LCs host, resulting in the decrease of the random lasing. A strong random lasing emission can reappear once the LC-fluctuation-induced destructive scattering is disappeared as the LCs becomes isotropic.
(3) All-optical controllability of the random lasing can be obtained by successively irradiating one UV and one green beam on the azo-dye-added DDLC with nanoparticles.The exposure of the UV (green) beam can cause the increase (decrease) of the LC-fluctuation-induced destructive scattering due to the trans→cis (cis-trans back) isomerization of the azo dyes. This may induce the decrease (increase) of the multiple-scattering effect of the nanoparticles in the LCs, resulting in the decrease (increase) of the random lasing emission.

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