高製程容忍度非偏振性非週期性晶疇極化反轉鈮酸鋰波導電光定向耦合器之研究;Study of fabrication-tolerant non-polarizing electro-optic directional couplers in aperiodically poled lithium niobate waveguide

Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/82794

Title:	高製程容忍度非偏振性非週期性晶疇極化反轉鈮酸鋰波導電光定向耦合器之研究;Study of fabrication-tolerant non-polarizing electro-optic directional couplers in aperiodically poled lithium niobate waveguide
Authors:	鄭又寧;Cheng, Yu-Ning
Contributors:	光電科學與工程學系
Keywords:	鈮酸鋰;定向耦合器;非偏振性;非週期;電光;Lithium Niobate;directional couplers;non-polarizing;aperiodic;electro-optic
Date:	2020-03-13
Issue Date:	2020-06-05 17:12:59 (UTC+8)
Publisher:	國立中央大學
Abstract:	本研究中我們運用新開發的一種獨特非週期性調整∆β的概念在鈮酸鋰波導上來實現高製程容忍度非偏振性電光定向耦合器。在Z-cut鈦擴散鈮酸鋰波導上利用模擬退火法優化後的非週期性晶疇反轉結構來達到高頻寬(通訊波段中的S-C-L)不分偏振(即對於TE與TM偏振態)的高分光比調控。與傳統週期性結構定向耦合器相比，本技術能夠訂製和實現出高製程容忍度與高工作頻寬的耦合器開關，對於建構積體光子開關網路和積體量子光路具有很大的吸引力。運用單一晶疇極化反轉結構(非週期晶疇極化反轉結構)來設計出可控制TE和TM偏振光非週期性晶疇極化反轉鈮酸鋰(APPLN)定向耦合器元件的輸出表現。我們通過施加適當的電壓(電光性)在1550 nm波段附近可以達到快速且同時擁有高分光比(設計上分光比99%) TE或TM偏振光耦合器的輸出表現。我們在長度為50mm，寬度為18mm，厚度為0.5mm的Z-cut鈮酸鋰晶片上製作了多組不同參數的定向耦合器。製程上我們使用標準的黃光微影技術來製作鈦金屬定向耦合器結構，然後使用高溫擴散製程製作出鈦擴散波導定向耦合器，再來利用高電場極化反轉製程製作出非週期性晶疇極化反轉結構，接著將晶片端面經過10o角拋光，之後在定向耦合器的耦合區中將條型鋁電極鍍在波導緩衝層(〖SiO〗_2)上完成元件的製作。最後我們量測了元件的耦合特性。我們把量測結果加上製程誤差與量測誤差的分析後與模擬結果相擬合。在未來的工作上，特別是在積體光學元件和量子光子元件中，我們可以通過該技術設計和製作出不同的非週期結構來實現多樣的電光控制光邏輯閘與光開關應用。 ;In this study, we develop a unique aperiodically alternating- scheme in LiNbO3 waveguides for realizing fabrication-tolerant non-polarizing electro-optic (EO) directional couplers. An optimized aperiodic domain inversion structure in titanium-diffused z-cut LiNbO3 waveguides was calculated by using simulated annealing method to achieve a high power-extinction switching of a wave in a broad telecom (S-C-L) band regardless of its polarization state (i.e., for both TE and TM polarized modes). Compared with conventional directional couplers based on periodic structure, this technology enables that the switching behavior of a coupler can be tailored and realized with high fabrication tolerance and broad working-bandwidth, attractive for building integrated photonic switching networks and on-chip quantum photonic circuits. The aperiodically poled lithium niobate (APPLN) coupler device is designed to switch both the TE and TM polarized light in a single poling structure (aperiodic domain inversion structure). With the application of appropriate voltages, either TE or TM polarized light in a band around 1550 nm can be fast (electro-optically) switched with high power extinction ratio (99% by design). We fabricated a set of directional couplers in a single z-cut LiNbO3 chip of 50 mm in length, 18 mm in width, and 0.5 mm in thickness. Mainly, a standard lithographic process was used to produce a titanium directional coupler structure, and then a high temperature diffusion process was used to form the waveguides. The aperiodic domain structure was then produced in the couplers by using the standard electric-field poling technique. The end faces of the chip were then 10o angle polished without applying any optical coating on them. The device fabrication was accomplished after the coating of the stripe electrodes (Al) over the waveguides buffered by an oxide (SiO2) layer in the coupler sections for the voltage application. Finally, we measured the coupling performance of the fabricated devices. The results have been fit with the simulations, in which the possible fabrication and measurement errors have been analyzed. In the future, different aperiodic structures can be designed and implemented in this technique to realize versatile electro-optically controlled optical logic gates and optical switches for many applications in especially integrated optical and quantum photonic devices and circuits.
Appears in Collections:	[Graduate Institute of Optics and Photonics] Electronic Thesis & Dissertation

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