以非週期晶疇極化反轉鈦擴散鈮酸鋰波導晶片產生偏振糾纏光子對;Nonperiodic optical superlattice lithium niobate waveguides for the generation of polarization entanglement

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題名:	以非週期晶疇極化反轉鈦擴散鈮酸鋰波導晶片產生偏振糾纏光子對;Nonperiodic optical superlattice lithium niobate waveguides for the generation of polarization entanglement
作者:	蘇文銓;Su, Wen-Chiuan
貢獻者:	光電科學與工程學系
關鍵詞:	鈮酸鋰;非週期;波導;偏振糾纏;量子光源;lithium niobate;nonperiodic;waveguide;polarization entanglement;quantum light source
日期:	2020-03-13
上傳時間:	2020-06-05 17:12:53 (UTC+8)
出版者:	國立中央大學
摘要:	本論文順利開發出了基於非週期晶疇極化反轉(NPPLN)鈦擴散鈮酸鋰波導晶片的非簡併偏振相關光子對光源，用基因演算法來優化非週期結構中所對應到的自發參量下轉換過程(SPDC)並使其達到最大與相等效率值，我們首先模擬出產生雙光子對的自發參量下轉換光源其特性，之後製作出此晶片並進行量測。我們用古典的和頻實驗(SFG)來量測我們的NPPLN波導SPDC光源，我們發現峰值波長會隨著溫度改變出現藍移的現象，其值為0.23 nm/℃，與我們模擬的結果(0.25 nm/℃)相符合。在使用頻寬更寬的雷射進行實驗後可以在光譜上發現兩個峰值，當實驗溫度為220℃時，我們量測到的兩個峰值波長分別為1570.17 nm與1580.71 nm，其頻寬分別為0.30 nm與0.31 nm。從汞浦光能量與訊號光能量的關係為一二次曲線可以說明這是一個二次非線性過程。在SFG量測中可以看到兩道強度相等的直線代表了非週期結構中所包含的兩個主要的type-II相位匹配，從此結果可以預測出有兩對偏振糾纏光子對波長分別為1566 nm與1585 nm，並且透過SFG對SPDC的轉換原理可以知道是透過汞浦光波長為787.8 nm來產生。在未來我們可以在同一片晶片中透過在SPDC後段加入一段結構稱為電光模態耦合器(EOPMC)來更進一步消除因為雙折射晶體所造成的光子對間的時間延遲。 ;In this study, we develop a nondegenerate polarization-correlated photon-pair source based on titanium-diffused nonperiodically-poled lithium niobate (NPPLN) waveguides. The nonperiodic domains are optimized using a genetic algorithm to maximize and equalize efficiencies of the respective spontaneous parametric down-conversion processes. We have first simulated the performance of the novel NPPLN spontaneous parametric down conversion (SPDC) source for dual photon-pair generation and then fabricated and characterized the device. We characterize the NPPLN waveguide SPDC source by means of classical sum-frequency generation (SFG) measurements. We found the peak wavelengths will have a blue shift of 0.23 nm/℃ with temperature tuning, which agrees well with the simulation result (0.25 nm/℃). We can see two peaks in the spectrum when we using the wider wavelength range laser source. At 220oC, we measured dual spectral peaks at 1570.17 nm and 1580.71 nm with bandwidths of 0.30 nm and 0.31 nm, respectively. The measured relationship between the pump power and signal power is a quadratic curve which is a signature of 2nd order nonlinear process. In the measurement, two SFG maxima of equal amplitude corresponding to the two main components of the dual type-II quasi-phase-matching conditions can be observed, from which we can predict that there will be two polarization entangled photon pairs with wavelengths at 1566 nm and 1585 nm, respectively, generated by a pump at 787.8 nm according to the correspondence theory between SFG and SPDC. In the future, we can add a structure called electro-optic polarization mode converter in the same chip with the SPDC source to further eliminate the time delay between the photon pairs caused by the birefringence of the crystal.
顯示於類別:	[光電科學研究所] 博碩士論文

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