| 摘要: | 本研究分別以近紅外光之連續式雷射及奈秒脈衝式雷射對無鹼玻璃進行結 構改質，運用近紅外光於玻璃高穿透度之特性，可於玻璃上下表面形成一對共軸 的改質區，由於雷射能量為高斯分布因此產生拱頂型的結構改質區，本文首先會 探討玻璃對近紅外波段能量的吸收機制及改質區形成機制，並以不同的雷射功率、 照射時間及脈衝頻率來觀察其對改質區結構的影響。在表面輪廓部分，本研究主 要探討的雷射能量區間為 30 W 至 50 W，可產生高度區間約為 100 nm 到25 μm 以及寬度區間20 μm 到 100 μm 之改質區，當雷射能量條件未能使玻璃達到玻璃 轉換溫度之上時，並無法產生結構改質區，當能量上升至適當範圍內，改質區高 度、寬度及體積機會隨著能量上升而增加，隨著能量在提升，改質區的寬度及體 積仍然呈現增加的趨勢但高度則呈現負成長，在能量強度過於極端的條件下，玻 璃會產生激烈的汽化反應而燒蝕。脈衝式雷射的部分，在相同的脈衝能量及脈衝 數量下，在雷射頻率較高時，具有較顯著的熱累積效應，可以獲得較大的改質區。並透過調整聚焦位置來改變改質區上下改質區的大小，結果顯示在負離焦的情況 下可以在下表面產生較大的改質區，並利用應力分析儀檢測改質區之應力分佈。本研究所產生之改質區表面粗糙度(Ra)可達 15 nm 以下，可達光學應用的規格,透過振鏡系統之定位可於玻璃基板上製作雙面微透鏡陣列，並以直徑 50 μm 的 微透鏡來探討其最佳化的陣列間距，在過小的間距，微透鏡在成形時會互相干擾 產生尺寸上的不平均，最後得到在微透鏡間距為 50 μm 時，尺寸差異之標準差可 以降至0.23，可產生均勻之陣列結構。;In this study, the structure modification on the alkali-free glass was carried out near-infrared continuous wave laser and nanosecond pulsed laser. Due to high transmittance of near-infrared light on the glass, a pair of coaxial modified zone were formed on the upper and lower surfaces of the glass. Because the laser energy is Gaussian distribution, a dome-shaped structural modification zone is produced. This article will first discuss the absorption mechanism of the glass to the near-infrared band energy and the formation mechanism of the modification zone. Different laser powers, irradiation time and pulse frequency were used to observe their influence on the structure of the modified zone. In the surface profile, the laser energy range that this study mainly discusses from 30 W to 50 W, which can produce a modified zone with a height range of about 100 nm to 25 μm and a width range of 20 μm to 100 μm. When the laser energy condition cannot make the glass to reach above the glass transition temperature, the structural modification zone cannot be produced. When the energy rises to an appropriate range, the height, width and volume of the modification zone increase with the increase of energy. As the energy increases, the width and volume of the modified zone still show an increasing trend, but the height shows a negative growth. Under conditions of excessive energy intensity, the glass will undergo a fierce vaporization reaction and ablation. For pulsed laser, under the same pulse energy and number of pulses, higher laser frequency has more significant heat accumulation effect and a larger modified area can be obtained. By adjusting the focusing position can change the size of the upper and lower modified areas, the results show that in the case of negative defocus, a larger modified area can be generated on the lower surface. Stress analyzer is used to detect the stress distribution of the modified area. The surface roughness (Ra) of the modified area produced in this research can reach 15 nm or less, which can reach the specifications for optical applications. Through the positioning of the galvanometer system, a double-sided microlens array can be made on a glass substrate. Microlens with a diameter of 50 μm was used to discuss the optimal array pitch. When the pitch is too small, the microlenses will interfere with each other and cause dimensional unevenness during forming proces. Finally, when the microlens pitch is 50 μm, the standard deviation of the size difference can be reduced to 0.23, a uniform array structure can be produced. |
