摻雜氧化鎂鈮酸鋰準相位匹配大溫度頻寬綠光倍頻雷射晶片研製

Abstract

本篇論文主要以摻雜氧化鎂鈮酸鋰為材料，研製週期性極化反轉倍頻雷射晶片，目標為利用此晶片達成輸入1064nm紅外光準相位匹配倍頻產生532nm綠光。 製程部分以未摻雜共熔鈮酸鋰(CLN)高電壓致極化反轉經驗為基礎加以改良，在厚度為0.5um摻雜氧化鎂鈮酸鋰(MgO:LN)晶片成功研製出最小週期為6.91um第一階一維和多週期第一階一維週期性結構；在厚度為1um摻雜氧化鎂鈮酸鋰(MgO:LN)晶片也成功研製出13.8um第二階一維及6.94um第一階準一維的週期性結構。 光學實驗部分只對0.5um厚摻雜氧化鎂鈮酸鋰(MgO:LN)晶片做討論。單週期結構、長度5um，以170MW/cm2(180mW) 光腰半徑60um奈秒泵浦條件下，產生80mW的綠光輸出、轉換效率約在46%；並在區段啁啾結構設計下，於多週期結構、長度5um，以195MW/cm2(350mW)光腰半徑75um之奈秒泵浦條件下，產生63mW的綠光輸出，轉換效率約20%，且可接受溫度頻寬達50度。相較於同樣長度單週期設計，雖然轉換效率降低了2.3倍，但提升了10倍的可接受溫度頻寬。

This thesis reports the fabrication of periodically poled magne-sium-oxide-doped congruent lithium niobate (PPMgLN), to convert the 1064nm infrared laser into 532nm green light by using the technique of quasi-phase matching second harmonic generation(QPM-SHG). We improved the fabrication technique on electric poling method of congruent lithium niobate. This method leads to the realization of periodically poled QPM structures on 0.5mm and 1mm thick MgO:LiNbO3 substrates. The smallest periods achieved in this work are (i) 6.91um for the 1st - order 、(ii) chirped-gratings for the 1st-order QPM device. For the 1mm thick substrate , the smallest periods we can make are (i) 6.96um for the 1st-order quasi-1D、(ii)13.8um for the 2nd–order QPM device. For the characterization we measured SHG on PPMgLN with 5mm crystal length when pumped by a pulsed 1064nm laser of 159 MW/cm2 (180mW) with 5ns pulse width of 60um beam waist. The device exhibits 80mW green light output with conversion efficiency attain 46% . Second, the design of chirped grating structure with 5mm long are tested by a pulsed 1064 nm laser of 195 MW/cm2 (350mW) with beam radius 75um. The device exhibits 63mW green light output with the conversion efficiency 20%, and the acceptance temperature bandwidth is about 50 degree. In the same length, the acceptance temperature bandwidth for the segment-chirped design exceeds that of single period by a factor of 10, whereas the conversion efficiency is reduced only by a factor of 2.3 .