研究摻鐿鎢酸釓鉀單晶雷射在低溫下的時空動態與輸出性能

Abstract

本論文在闡述掺鐿鎢酸釓鉀單晶雷射在低溫系統中之相關研究。首先我們探討準三能階雷射的基本特性，並量測掺鐿鎢酸釓鉀晶體在各溫度下不同偏振的螢光特性，接著觀察掺鐿鎢酸釓鉀單晶雷射在各溫度下的輸出特性與時間動態行為。我們利用理論分析準三能雷射等效損耗隨溫度的變化，與實驗現象所呈現趨勢相當吻合，發現透過低溫冷卻能有效地降低再吸收損耗，使得雷射輸出效率有顯著提升，大約在溫度110 K附近達到最大值，並且在各溫度下同時觀察到自發性鎖模與自發性Q開關的輸出。隨著系統溫度的下降，Q開關脈衝的重複率變得更快，脈衝能量也有顯著提升，且峰值功率相較於室溫狀態下提升了大約7倍。我們成功地展示了同時具自發性鎖模與Q開關脈衝的掺鐿鎢酸釓鉀單晶雷射，並發現透過低溫冷卻能夠有效地提升雷射的輸出品質，期望在未來能夠提供更好的應用。

This thesis elaborates the research of monolithic Yb:KGW lasers at cryogenic temperatures. First, we investigate the properties of the quasi-three-level laser, and then measure the polarized fluorescence spectra of Yb:KGW at cryogenic temperatures. We further explore the output performance and temporal behavior of monolithic Yb:KGW lasers at cryogenic temperatures. Experimental results are fairly consistent with the theoretical analysis of the temperature-dependent reabsorption loss of the quasi-three-level laser. We observed that the laser output efficiency can be significantly improvedthrough cryogenic cooling due to the effective elimination of reabsorption loss, and the output power reached a maximum value at the approximate temperature of 110 K. Self-mode-locking and self-Q-switching were verified to simultaneously exist at various temperatures. As the temperature deceased, theQ-switched pulse repetition rate and pulse energy increased, and the peak power raised about 7 times compared to the room temperature. We successfully demonstrated a simultaneously self-Q-switched and self-mode-locked monolithic Yb:KGW laser and the laser output quality can be effectively improved by cryogenic cooling. We wish our research would provide useful applications in the future.