寬頻液晶空間相位調制器

Abstract

由於阿秒雷射系統中需要運用從紅外光至紫外光下的光源，因此我們目的製作可調變此波段下的脈衝光源的液晶空間相位調變器。 觀察液晶面板技術中，其結構的各部份對於非可見光的波段有極高的吸收度，常使用的導電薄膜為氧化銦錫，其對於紫外光和紅外光有極高的吸收。為滿足寬頻波段使用，由鎢化錫和氧化銦錫奈米柱結構取代為導電膜。對於鎢化錫薄膜我們改變濺鍍的時間和使用的濺鍍功率。氧化銦錫奈米柱結構則是使用e-gun改變厚度和製程參數，找到可使高穿透並且可接受片電阻之最佳化製程參數。我們也探討各種不同配向膜製作上最佳配向參數需要，以及對於紅外光與紫外光的使用上優劣比較。液晶雖已經使用80%以上穿透率的液晶，卻會受到紫外光的影響，造成元件性質被改變。對355nm波長脈衝光做元件光生命期的量測，可以找出在355nm波段使用下元件生命期和調變能力的改變與入射脈衝光的雷射光束尺寸以及單位面積紫外光源強度的關連性。

The goal of this project is to develop a liquid crystal spatial light modulator (SLM) that covers the range from the ultraviolet to the infrared that is suitable for use in modulating light in the attosecond regime. Commercial SLMs are primarily for use in the near-ir and the visible from 1600 nm to 430 nm. They use ITO as the electrode material that has a high absorption in the uv and the infrared. In order to satisfy our requirement, we tested both TiW and nanorod ITO as replacement of ITO as the electrode material. TiW was deposited onto the substrate by DC sputtering. For nanorod ITO we used e-gun deposition. In both cases the deposition parameters were optimized to vary the thickness and resistivity of the thin film electrode for the most suitable performance. For the alignment layer suitable materials include Nissan 130B, MAP, DMOAP and Fe2O3. We fabricated a number of devices and compared their performance as SLM in the uv and the ir. We find that in the uv the performance of the devices degrade with time although the overall device transmission is greater than 80%. Lifetime tests were done at 355 nm to obtain a connection between the lifetime and the beam size as well as the incident intensity of the uv light.