熱效應對連續波雷射與脈衝波雷射的影響:傳統晶體與鍵合晶體的比較

Abstract

摘要

本論文使用單一鍵合晶體能有效降低熱效應和提高雷射性能，由於雷射晶體前端為非摻雜的同質晶體，可使內部摻雜的雷射晶體激發所產生的熱，經由前端非摻雜的同質晶體均勻吸收熱的通過，有效地改善晶體中心和側面的溫度梯度，減少晶體端面，因熱變形所引起的熱透鏡效應，達到雷射晶體均勻的散熱，有利於雷射系統的穩定性及高功率運轉。

在本實驗中，使用端面激發固態二極體架構之連續波雷射與脈衝雷射的輸出，比較傳統Nd:YVO4與單一鍵合晶體YVO4/ Nd:YVO4對熱效應的影響。實驗中我們改變200mm、300mm、400mm腔長距離，以最大平均輸出功率的比較，在連續波雷射的輸出，單一鍵合晶體比傳統晶體分別增加了42%、74% 和99% 。在脈衝雷射的輸出，單一鍵合晶體對熱效應的改善遠大於傳統的晶體，最大可增加到168%，由實驗證實鍵合晶體能有效減少熱效應。因此將單一鍵合晶體應用在被動式半導體鎖膜雷射的操作中，發現可獲得較寬廣的脈衝寬度，利用鍵合晶體非摻雜的部分，可減少spatial-hole-burning(SHB)的效應，獲得更寬的脈衝寬度。

Abstract

The composite crystal, which is fabricated by the diffusion bonding of a doped crystal to an undoped crystal as a heat sink for the pump surface, can efficiently reduce the thermal-induced problems such as thermal lensing, thermal distortion, thermal fracture and so on. As a result, the composite crystal is expected to be potentially beneficial for laser power-scaling as well as power-stability enhancement. In this thesis, we design a scheme of a diode-pumped solid-state laser to comparatively study the thermal effects between the conventional crystal and composite crystal under continuous-wave (cw) and pulsed operation. In cw operation, the maximum average output power of composite crystal were 42%, 74%, 99% larger than the results obtained with conventional crystal in the cases of L=200mm, L=300mm, and L=400mm, where L is the cavity length. In pulsed operation, the improvement of laser performance with the composite crystal was also realized due to the reduction of thermal effects compared with the conventional crystal. Furthermore, we observed that the mode-locked pulse width obtained with the composite crystal was considerably broader than that obtained with the conventional crystal. The pulse broadening was experimentally verified to come from the length of the undoped part that brings in a reduction of the spatial-hole-burning (SHB) effect.