| 摘要: | 近年來，鈮酸鋰薄膜問世，各國積極透入在鈮酸鋰薄膜上光學或光電元件的研究與開發，在本論文中，我們首先比較鈮酸鋰薄膜與傳統鈮酸鋰基板的不同與其優勢之處，並且探討鈮酸鋰薄膜製程的困難點，接著我們將在薄膜上開發電光偏振轉換器元件，因此我們會先以理論介紹何謂波導、電光效應以及索爾克濾波器，並且結合這三者的概念組成電光偏振轉換器。
模擬方面，首先模擬波導結構，包含波導寬度、蝕刻深度、側壁角度，此三個參數會影響到單模條件以及等效折射率，再利用模擬得到的等效折射率計算出所需的Poling週期，電光效應方面，我們模擬實際所需要的工作電壓以達到相對應的需求電場。
製程方面，我們比較不同蝕刻方法所製作出來的波導平整度，再以最終決定的蝕刻方法所製作出來的波導結構去模擬單模條件、等效折射率及所需的Poling週期，接著是Poling的參數測試以及結果量測，找到最適合的Poling參數，再將其與波導結合，形成週期性極化反轉波導，最後透過半導體製程將電極製作在波導上方及兩側以利在量測時施加電壓。
量測方面，首先是波導的損耗量測，本論文所製作出來的波導損耗為3.62dB/cm(TE)、2.41dB/cm(TM)，是相較於本實驗室以往做出來的波導裡損耗最小的，接著是EOPMC量測，我們在80℃時量到94%的轉換效率，而最高轉換效率在92℃，約為99%，並且量測其不同溫度時中心波長的位移。
不同於傳統被動元件，本論文所製作出來的電光偏振轉換器作為主動元件，有體積小且可以主動調節TE和TM之間的轉換等優勢，此元件在鈮酸鋰薄膜的光學研究與發展上會是很重要的一大進步。;In recent years, lithium niobate thin film has emerged, and countries are actively engaging in research and development of optical or optoelectronic devices based on these lithium niobate thin film. In this thesis, we first compare the differences and advantages of lithium niobate thin films with traditional lithium niobate substrates, and discuss the challenges of the thin film fabrication process. We will then develop an electro-optic polarization mode converter device on the thin film. To start, we will introduce the concepts of waveguides, electro-optic effects, and solc filters, integrating these three concepts to form the electro-optic polarization converter.
In terms of simulation, we will first simulate the waveguide structure, including waveguide width, etching depth, and sidewall angle. These three parameters will affect single-mode conditions and the effective refractive index. We will then calculate the required poling period using the effective refractive index obtained from the simulation. Regarding the electro-optic effect, we will simulate the actual working voltage needed to achieve the corresponding electric field.
In the fabrication process, we will compare the waveguide smoothness produced by different etching methods. We will then use the final chosen etching method to simulate the single-mode conditions, effective refractive index, and required poling period. Following this, we will test the poling parameters and measure the results to find the most suitable poling parameters, which will then be combined with the waveguide to form a periodically poled inverted waveguide. Finally, we will use semiconductor processing to fabricate electrodes on the top and sides of the waveguide to facilitate voltage application during measurements.
In terms of measurement, we will first measure the waveguide loss. The waveguide loss produced in this thesis is 3.62 dB/cm (TE) and 2.41 dB/cm (TM), which is the lowest loss recorded in our laboratory to date. Next, we will measure the electro-optic polarization mode converter (EOPMC). At 80°C, we achieved a conversion efficiency of 94%, and the highest efficiency, approximately 99%, was observed at 92°C. We will also measure the shift in the central wavelength at different temperatures.
Unlike traditional passive devices, the electro-optic polarization mode converter developed in this thesis serves as an active device, offering advantages such as a compact size and the ability to actively adjust the conversion between TE and TM modes. This device represents a significant advancement in the optical research and development of lithium niobate thin films. |
