幾何狹縫繞射

Abstract

中文摘要 本次雷射加工終端實作內容為，幾何狹縫圖形製作與繞射圖案探討，我們將分別觀察中空三角形、中空六邊形和中空5邊星形的狹縫，並以單狹縫繞射為基礎，作為多邊形狹縫之推論與分析參考。狹縫之製作方式，在玻璃基板上利用熱蒸鍍方式，將厚度約90 nm的鋁蒸鍍至玻璃表面，並利用一近紅外(1064 nm)脈衝光纖雷射加工機進行多邊形狹縫雕刻，當近紅外雷射照射在金屬鋁上，鋁金屬吸收雷射轉化為熱能，升溫達汽化溫度而剝除，達到雷射雕刻之效果。調整相關加工參數，使狹縫邊緣完整平滑，並且中心圖案能清除乾淨後，後續再架設光繞射/干涉量測裝置，進行繞射圖案的觀察與量測。用氦氖雷射照射多邊形狹縫並產生繞射圖案後，經過一個平凸透鏡將繞射圖案收集，達到遠場繞射條件，再以光束空間分析儀(Beam Profiler)進行空間之雷射光強度觀察，並以單狹縫為例，進行理論值與實驗值之誤差分析，誤差值為5.3%。 最後我們觀察的光形分佈圖案符合參考文獻的結果，繞射圖案會依據多邊形狹縫的邊長數量而有相對應方向的繞射圖案，同時透過狹長的邊長所產生的繞射圖案會有對稱性,若邊長為互相平行，則有干涉現象出現且有明顯的亮暗條紋。

英文摘要 The practice project on laser material processing is to investigate the production of geometric slits and the study of diffractive patterns. We will observe the slits of hollow triangles, hollow hexagons and hollow five-sided stars, respectively, and use single-slit diffraction as a reference to calculate the error between the experimental and theoretical analysis. The slits are fabricated on the glass substrate coated with aluminum by thermal evaporation. The thickness was estimated ~90 nm. The polygonal slit engraving was performed using a 1064 nm pulsed fiber laser processing machine. When the laser is irradiated on the aluminum, the metal absorbs the laser energy and converts it into heat, which is heated up to the vaporization temperature and aluminum is stripped. After adjusting the controlled processing parameters so as to make the edge of the slit more smoothly and the central pattern can be cleaned up, we will observe the diffraction pattern by installing a light diffraction/interference measuring device. After irradiating the polygonal slits with a HeNe laser and generating a diffraction pattern, the diffraction pattern is collected by a plane-convex lens to achieve the far-field diffraction conditions, and then the laser intensity of the space is observed through a beam profiler. Taking the single slit as an example, the calculated error was reached 5.3 % between the theoretical value and the experimental value. Finally, the diffraction patterns we observed are consistent with the published results. The diffraction patterns have a corresponding pattern with the number of sides of the polygonal slit. If the side length is parallel to each other, then the interference patterns modulated by diffraction will be observed.