退火式質子交換波導PPLN電光調制TM模態轉輻射偏振態之研究;Guided-to-radiation polarization mode conversion in electro-optic PPLN APE waveguides

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題名:	退火式質子交換波導PPLN電光調制TM模態轉輻射偏振態之研究;Guided-to-radiation polarization mode conversion in electro-optic PPLN APE waveguides
作者:	鄧聖龍;Sheng-long Teng
貢獻者:	光電科學研究所
關鍵詞:	波導;極化反轉;質子交換;鈮酸鋰;LiNbO3;waveguide;APE;PPLN
日期:	2008-07-09
上傳時間:	2009-09-22 10:35:53 (UTC+8)
出版者:	國立中央大學圖書館
摘要:	波導振幅調制器為光通訊、波導雷射中具有重要應用價值的元件。本研究是在z 切面( z-cut )鈮酸鋰( LiNbO3 )基板上製作退火式質子交換波導 ( Annealed Proton Exchange waveguide，簡稱APE 波導 )，利用APE 波導只能傳播TM 模態的傳播特性，再利用週期性極化反轉鈮酸鋰( PPLN )的準相位匹配技術作電光調制，將波導TM 模態的能量偶合至APE 波導無法傳播的TE 波，形成TE 波的能量損耗，使得TM 模態無法獲得TE 波的能量回饋，因此可以在APE 波導上達到TM 模態的振幅調制功能。本研究的工作波長設計在通訊波段( 1550nm )，波導寬度設計為12μm，深度4.07μm，週期性極化反轉結構則是利用索爾克( Solc filter )濾波器[6]的半波板概念並設計三種週期作比較，分別是23.7μm、24μm、24.3μm。當外加工作電壓250V，TM 模態可以達到帶寬80nm，大於50%的能量損耗，而在能量轉換效率最好的波長更可得到大於70%以上的能量損耗。在經過模擬分析之後，我們可以估計TE 波在傳播的損耗約在0.07dB/ μm ~ 0.09dB/μm，而製程上週期設計的可容忍誤差更可以達到2μm。Waveguide amplitude modulator is essential device of optical communication. We designed and fabricated the annealed proton exchange waveguide ( APE waveguide ) on z-cut lithium niobate ( LiNbO3 ) substrate. According to former research, we knew that APE waveguide can only guide TM polarized mode. We used these properties of APE waveguide and periodic poled lithium niobate ( PPLN ) quasi-phase matching technique to achieve electro-optic modulation. Our main purpose is transforming the guided energy of TM mode to TE unguided radiation wave via PPLN electro-optic modulation. The energy coupled to TE unguided wave has energy loss and the TM guided mode can’t acquire the energy feedback from TE wave, therefore we can accomplish amplitude modulate in APE waveguide. We design the device at the wavelength of telecommunication ( 1550nm ), the channel opening and waveguide depth is 12μm and 4.07μm. The period design of PPLN is base on the concept of half wave plate in “Solc filter[6]’’. In order to compare the experimental result, we design three different period in this device : 23.7μm, 24μm , and 24.3μm . When applied external voltage at 250V, the loss of TM mode is more than 50% and the spectral bandwidth is about 80nm. Additionally, the loss of TM mode is more than 70% near the phase match wavelength. According to the computational modeling, we estimate the loss of TE wave is about 0.07dB/μm ~ 0.09dB/μm, and the fabrication process of period tolerance is about 2μm.
顯示於類別:	[光電科學研究所] 博碩士論文

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