高功率雷射光束品質改進與雷射鑽孔之應用

Improving the beam quality of high power laser field and the application on laser drilling

蔡宇亮(Yu-Liang Cai)

指導教授 ： 潘犀靈

國立清華大學/理學院/物理學系/碩士(2012年)

摘要

高功率雷射在放大過程中，容易產生高頻空間訊號，造成雷射光斑有缺陷。因此，我們需要設計一個光學空間濾波器改善實驗系統中高功率窄頻Nd:YAG雷射光斑。根據透鏡的傅立葉轉換特性，光束在焦平面上會產生傅立葉頻譜，空間頻率越高會分布在越外緣，利用適當大小的孔洞可以過濾高頻空間雜訊，使雷射光斑獲得改善。我們使用圓錐狀的孔洞，與傳統圓形孔洞相比較，此圓錐狀設計可以增加孔洞材料承受雷射能量的面積，增加孔洞的壽命。孔洞固定在玻璃真空管中以降低空氣中電漿的產生與孔洞的損害。我們使用尺寸最小的孔徑為380微米，材料為不銹鋼。實驗結果顯示雷射光斑品質已明顯改善，且孔洞可承受雷射強度16.9 TW/cm2。另外，我們應用此空間濾波器在相位量測系統與雷射加工上，也明顯提高干涉條紋在空間上的穩定與加工的品質。

關鍵字

空間濾波器 ； 高功率 ； 光束品質 ； 雷射鑽孔 ； 雷射光班

並列摘要

In amplification of high-power laser, the high-spatial-frequency components are generated usually, causing the defect in laser beam profile. Therefore, we design an optical spatial filter to improve the beam profile of narrow-band Nd:YAG laser in our experimental system. According Fourier optics, Fourier power spectrum is produced in the focal plane of lens. The higher spatial-frequency components are located at the position far from optical axis. Thus, an aperture with proper size can be used to remove high-spatial-frequency noise so that the beam profile is improved. We apply an aperture with conical shape. This design can increase the interaction area of incident beam and material surface lead to longer lifetime for aperture. In order to reduce the air plasma and damage of aperture, we fix the aperture in a glass vacuum tube. The minimum aperture size is 380 μm and material is stainless steel. Experimental results show the beam profile is improved obviously and the aperture can tolerate intensity 16.9 TW/cm2. Besides, we apply this spatial filter to the phase measurement system and laser processing. The spatial stability of interference pattern and the quality of laser processing are better than before.

並列關鍵字

spatial filter ； high power ； beam quality ； laser drilling ； laser beam profile

參考文獻

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