| Summary: | 碩士 === 國立清華大學 === 物理系 === 100 === 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.
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