為了偵測到更微小的重力波訊號、觀察到更多的天體變化，提升干涉儀的靈敏度是必須的。提高干涉儀靈敏度的關鍵之一在於能否降低光學薄膜的熱擾動。根據Fluctuation-Dissipation Theorem，可知熱擾動正比於光學薄膜的溫度與機械損耗。此外，薄膜的光學吸收也是重點，過高的光學吸收會導致訊號的強度減弱。故本實驗室致力於開發具有低的低溫機械損耗與低光學吸收的光學薄膜。

我們使用離子束濺鍍法研究二氧化矽、二氧化鈦與奈米多層膜結構光學特性。使用此方式鍍製出的二氧化矽與二氧化鈦其消光係數皆在低階10-5數量級，而將兩種材料堆疊為奈米多層膜結構後，光學吸收在此結構下沒有明顯的影響。接著在進行600oC退火後，二氧化矽的消光係數有著顯著的改善，二氧化鈦的消光係數亦有改善但並不明顯。

在先前研究PECVD鍍製的氮化矽薄膜中發現，薄膜內的N-H鍵、矽懸鍵與光學吸收呈正相關，Si-H鍵則是會有Two-level system而影響到室溫的機械損耗。故計畫使用離子束濺鍍法鍍製氮化矽薄膜。於研究中發現，使用濺鍍法鍍製的氮化矽薄膜內，含有預期外的Si-H鍵及較多的矽懸鍵，且薄膜的消光係數也達到10-2數量級，愈使用在高反射鏡上是還有待改善的。

To detect gravity signals and observe more celestial changes. It is necessary to increase the sensitivity of the interferometer. One of the keys to improve the sensitivity of the interferometer is whether it can reduce the thermal noise of the optical film. According to Fluctuation-Dissipation Theorem, we can know that thermal perturbation is proportional to the temperature and mechanical loss of the optical film. Besides, the optical absorption of the film is also essential. If the optical absorption is too high, the intensity of the signal is lowered. Therefore, we are committed to the development of optical films with low mechanical loss at low temperatures and low optical absorption.

We study optical properties of silica, titania, and nano-layer structure deposited by ion beam sputtering. The extinction coefficients of silica and titania deposited by ion beam sputtering are 10-5 order, and after the two materials are combined into a nano-multilayer structure, optical absorption has no obvious influence under this structure. Then, after annealing at 600oC, the extinction coefficient of silica is improved obviously, and titania is also improved but not obvious.

In the previous study of silicon nitride film deposited by PECVD, we know that the N-H bond and silicon dangling bond in the film are proportional to optical absorption, and the Si-H bond is a two-level system that affects the mechanical loss at room temperature. Therefore, we use an ion beam sputtering method for coating silicon nitride film. In the research, we found the silicon nitride coated by sputtering method contains the expected Si-H bond and more silicon dangling bonds, and the extinction coefficient is 10-2 order. Consequently, using the film for high reflection mirror of interferometer still be improved.

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