光學濾波器對處理特定頻譜的光學訊號之系統是不可或缺的元件。窄頻濾波器對光學訊號處理及光通訊系統而言尤其需要。本研究目的是在電光週期性極化反轉鈮酸鋰(EO PPLN)波導上發展出超低工作電壓主動式窄頻光學濾波器。本實驗成功的在電光週期化反轉鈮酸鋰波導上做出應用在光通訊波段的高效率索爾克波長濾波及TE ?TM模態轉換器。本元件可擁有與大部份光通訊元件更高相容性的超低操作電壓(TTL level)，及簡單的電極結構。且符合國際電信聯盟(ITU)所規定的窄頻寬通條件。
在本研究中，成功地利用鈦熱擴散及電場極化反轉技術製作出低傳撥損耗的週期性極化反轉鈮酸鋰鈦波導。其傳撥損耗量測得到 。對1-cm長的元件而言，可得到頻寬為 ，且在操作電壓為 得到模態轉換或頻譜穿透率可高於 ，其電壓對應的值為1.1 V×d (μm)/L (cm)。另外溫度對頻譜範圍的調變率為 。在光通訊及光學訊號處理系統的運用上，可藉由電光週期性極化反轉鈮酸鋰鈦波導的窄頻寬通及寬光譜工作範圍的特性來發展強大且吸引人的主動式元件。

Optical filters are indispensable elements to many optical systems for allowing the process of optical signals in specific spectral portions. Narrowband filters are particularly demanded in optical signal processing and communication. The purpose of this research is to develop ultra-low operating-voltage and narrow-band active optical filters based on electro-optic periodically poled lithium niobate (EO PPLN) waveguides. In this work, we have successfully implemented a highly efficient Šolc-type optical wavelength filter and a TE ?TM mode converter in the c-band telecomm wavelengths based on EO Ti:PPLN waveguides. This device can have an ultra-low (TTL level) operation voltage, is highly compatible to most telecomm devices, has a simple electrode configuration, and has a narrow band-pass width conformed to the International Telecommunication Union (ITU) grid standard.
In the research, we have successfully fabricated low-loss Ti:PPLN channel waveguides using the thermally Ti-diffused method and electric-field poling technique. This device has multiple channels with each allowing for passing an ITU-grid signal in telecomm c-band wavelength. The propagation loss of the Ti:PPLN waveguides were determined to be as small as 0.17 dB/cm. A mode conversion efficiency or a spectral transmittance of as high as 97% at a bandwidth of ~2.6nm was achieved with this 1-cm device at a very low work voltage of 22 V which corresponds to a normalized value of 1.1 V×d (μm)/L(cm). Its temperature tuned wide spectral working range at a tuning rate of was also demonstrated, showing the device the potential of being an electro-optic tunable filter (EOTF). The characterized narrow band-pass width and the capability of wide spectral working range make the developed EO Ti:PPLN waveguide device a powerful and attractive active device, for example, optical communication and signal process applications.

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