本論文主要研究於摻雜偶氮與雷射染料的液晶-聚合物混合薄膜之可雙光子調控隨機雷射的特性。實驗結果發現，照射強度遞增的綠光與照射時間遞增的強紅光可分別遞減與遞增地調控樣品之隨機雷射輸出強度。產生如此可雙光子調控隨機雷射的機制有二:
(1)由於樣品中棒狀的trans態偶氮染料受強度漸增的綠光照射後，會經由trans轉換為cis isomerization產生濃度漸增的彎曲狀cis染料，如此會擾亂樣品中液晶顆粒原本的液晶相趨向isotropic相的程度會漸增，這會造成原本處於液晶相的液晶顆粒折射率與聚合物折射率不匹配的情況，漸漸在強度漸增的綠光照射後變得越來越配。由於要產生隨機雷射是需要螢光於樣品中傳輸時有大量散射產生，當液晶顆粒與聚合物折射率變得越來越匹配時，樣品中螢光光子的擴散常數(或散射平均自由路徑)會變大，使得散射強度漸漸變弱，因此導致樣品的隨機雷射強度漸減。
(2)當經由綠光照射後導致樣品產生的隨機雷射輸出強度降低至很弱時，以ㄧ道強紅光照射樣品後，輸出的隨機雷射強度隨著紅光照射時間漸增而又漸增地回復。此乃由於處於彎曲狀的cis態染料被強紅光照射越久，經由cis轉換為tran isomerization過程回到棒狀的trans態染料越多，如此造成液晶顆粒回復到液晶相的程度越來越強，導致與聚合物折射率差越來越大，樣品中螢光光子的擴散常數又漸漸降低回來，使散射強度漸漸又變強回來，因此樣品的隨機雷射輸出強度又漸漸提升回來。

This thesis investigates a biphotonically controllable random lasing emission based on a dye-doped polymer-dispersed liquid crystal cell. Experimental results show that the intensity of the random lasing emission can decrease and increase with increasing the irradiated intensity of one green beam and decreasing the irradiated time of one red beam, respectively. The biphotoinc controllability of the random lasing emission can be attributable to two mechanisms:
(1)After the irradiation of the green beam with increasing intensity, the concentration of the rod-like trans dyes transforming to curve cis-isomers may increase so that the LC droplets can be disturb to gradually change from nematic to isotropic phase. This may cause that the refractive indices of the LC droplet and the polymer gradually becomes match, which will induce the decrease of the diffusion constant (or scattering mean free path) of the fluorescence photons and thus the decrease of the scattering strength; in turn, the random lasing emission will decrease.
(2)After turning off the green beam, the intensity of the random lasing emission can gradually recover once the cell is illuminated by one red beam with increasing irradiated time. This is because the concentration of the cis dyes transforming to the trans-isomers increases with increasing the irradiated time of the red beam via cis-trans back isomerization. The LC droplets will gradually recover from isotropic to nematic phase, and the refractive indices of the LC droplet and the polymer will gradually become mismatch. This will cause the increase of the diffusion constant of the fluorescence photons and thus the increase of the scattering strength; in turn, the intensity of the random lasing emission will gradually recover.

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