高功率固態雷射因熱透鏡效應的影響，使此類雷射的輸出在激勵功率之變化下，不易維持光束品質的穩定。本實驗室對此課題利用兩組平面反射鏡與凸透鏡的組合，分別置於棒型Nd:YAG晶體兩側的共振腔結構，已達成穩定輸出遠場發散角之初步結果。本論文延續此一成果，再進一步探討如何在更大的激勵功率變化之下使發散角更小，並同時降低近場光點的大小變化。使雷射光束的穩定性，在輸出功率由14瓦變化至87瓦的範圍內，遠場發散角的變率為?? / ? = 7.5%，近場光點半徑的變率為?w / w = 6.0%。 對於避免熱透鏡效應的方法，仍以各元件間距之調整，構成輸出光束品質穩定之單棒熱效應非敏共振腔。本文將介紹如何以高斯光束傳遞原則及ABCD矩陣法，建立共振腔模擬計算程式，來預測最佳之共振腔結構。 另觀測到緩熱效應（Less Heat Generation）對輸出光束之影響，並首先討論緩熱效應對共振腔穩定性所造成之改變。藉此可修正當雷射光束建立後之共振腔行為。 而依「對稱延展共振腔」的構想，可將前述之單棒熱不敏感共振腔串接為雙棒或多棒之熱不敏感共振腔。並在維持輸出光束品質的前提之下，可以有效地增加此固態雷射之輸出功率。 Two sets of reflective mirrors and convex lens on both side of the Nd:YAG rod in a laser resonator can keep the output beam quality steady by adjusting the positions of these optical components. We achieved a stable beam quality with ?? / ? = 7.5% and ?w / w = 6.0% within a 70 W range. A stimulating program was built to predict the output beam quality of various resonator configurations with the methods of Gaussian beam propagation and ABCD matrix method. The “Less-Heat Generation Effect” was observed in the beam pattern variation after the lasing process started. Its influence to the stability of a laser resonator was discussed firstly. This result could also improve the description of the dynamic behavior of a lasing resonator. With the idea of “symmetric extension of resonator”, two or more single rod thermal lensing insensitive resonators could be connected in series. The resultant two or multi-rods resonator could also keep output beam quality stable, and generates much higher power as well.
