寬頻準相位匹配非線性過程應用於綠光與藍光產生之研究

Abstract

本論文的研究主題為非線性光學中的頻率轉換，主要分成兩大部份：一、設計可接受溫度頻寬達50°C的週期性反轉摻雜氧化鎂鈮酸鋰(PPMgO:CLN)，並以實驗驗證其倍頻(Second harmonic generation)轉換效率及可接受溫度頻寬。二、使用共熔組成週期性反轉鉭酸鋰(PPCLT)，以綠光雷射當泵浦光源，實現基於單共振光參振盪器(singly resonant optical parametric oscillator)的藍光雷射與白光雷射實驗。 對長度5mm十週期PPMgO:CLN進行1064nm做泵浦源的單趟通過(single pass)倍頻實驗，其可接受溫度頻寬可達49°C，倍頻轉換效率超過20%；與同長度的單週期PPMgO:CLN相比，可接受溫度頻寬由5.?°C上升至49°C，最高轉換效率由6?%下降至27%。 藍光實驗方面，藉著多週期準相位匹配(Quasi-Phase-Matching)的設計，532nm綠光轉465nm藍光的斜線效率(Slope efficiency)達16%，465nm藍光的光譜線寬被擴展至將近1nm。藉著調變PPCLT週期的佔空比(duty cycle)，532nm綠光轉435nm藍光的斜線效率提昇至21%。 白光雷射實驗方面，當綠光泵浦光功率為370mW時，於25.1mm長的PPCLT上經由級聯光參振盪-倍頻產生25mW的465nm藍光，並經由光參振盪產生45mW的630nm紅光。適當地選擇剩餘的綠光功率，可以得到色度坐標為(0.3333, 0.3333)之100mW的白光。

The research topics of this thesis focus on quasi-phase-matching (QPM) frequency conversion using periodically poled lithium tentalate (PPLT) and periodically poled MgO-doped lithium niobate (PPMgO:LN). This thesis is mainly organized into two parts: (a) Structure design of PPMgO:LN with broadbandly accepted temperature bandwidth for second harmonic generation (SHG) and its experiment to verify the SHG conversion efficiency and the temperature bandwidth. (b) Design of PPLT for singly resonant optical parametric oscillator (SROPO) and using green pump laser for blue and white light generation. For the QPM SHG experiment with single pass configuration, 5mm long PPMgO:LN with ten QPM periodicities was pumped by a Nd:YVO4 Q-switched 1064nm laser. The accepted temperature bandwidth was found to be 49°C, and the conversion efficiency exceeded 20%. Compared with a 5mm PPMgO:CLN with single QPM periodicity, the accepted temperature bandwidth increases from 5.?°C to 49°C and the maximum conversion efficiency decreases from 6?% to 27%. For the up-conversion blue generation, with the design of multi-QPM periodicities for the cascaded OPO-SHG process, the slope efficiency for the 465nm blue generation, as pumped by a pulsed green laser, reacheed 16%. The linewidth of 465nm blue was broadened to be 0.78nm. By changing the duty cycle of the poling area in PPCLT, the slope efficiency of up-conversion 435nm blue generation increased to 21%. For the white generation experiment, we used a 25mm long PPCLT where OPO-SHG cascaeded process generates blue and OPO generates red. When the power of green pump reachesd 370mW, we observed simultaneous generation of 465nm blue laser with 25mW power and 630mW with 45mW. If proper power of residual 532nm green laser was selected, then white laser with 100mW power and chromaticity coordinate located in (0.3333, 0.3333) could be realized.