一些具有光折變效應的材料，被廣泛應用在雙光束耦合(two-beam coupling)的相關研究上。在這篇論文中，我們以「液晶－聚合物」混合薄膜作為材料，以氬離子雷射作為記錄之雷射光，在形成全像光柵的動態過程中，引起了類似光折變效應的情形，我們可以藉著雙光束耦合的實驗觀察來證實這個類似於光折變的效應是存在的，同時藉由耦合模式理論的推導及實驗上之配合作更深入的探討。

本論文著重於強調－全像光柵形成之動態過程中，其能量耦合強度隨時間變化之情形及當兩道同調性高的記錄雷射光強度比值不同時，其能量耦合強度和兩道記錄雷射光強度比值的關係。經由能量耦合強度隨時間變化之動態過程的探討，我們更確信－引起類似光折變效應是由密度光柵和反遷移相位光柵所造成的影響；此外藉由能量耦合強度和兩道記錄雷射光強度比值之關係的討論中，我們發現隨兩道光強度的比值變大時，耦合強度卻相對變小；主要的原因為光強度比值漸漸變大時，干涉條紋之可見度將隨之漸漸變差，於是造成光柵折射率的調變量變小，耦合量便隨之變小。

Two-beam coupling (TBC) of photorefractive materials has been extensively studied recently. This thesis studies the TBC effect during the formation of a holographic grating in polymer-dispersed liquid crystal (PDLC) films pumped by two coherent Ar+-laser beams. This TBC is due to a non-stationary grating effect instead of the general photorefractive effect. Detailed discussion of the experimental results based on the TBC theory are made.

The thesis emphasizes the studies of the dynamic coupling strength
(gd ) during the formation of the grating , and of the relation between the coupling strength (gd ) and the power ratio of the two pump beams(mo) .
The measured results confirm that the photorefractive-like effect observed in PDLC grating is attributable to the formation of the density grating and the reverse-diffusion grating. Furthermore , the results also show that the coupling strength decreases with increasing mo. The cause is believed to be due to the decrease of the Fringe visibility of the interference , which , in turn, reduce the refractive index modulation of the grating while the beam power ratio is increasing.

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