| 摘要: | 本研究旨在開發二步驟雷射照射法應用於薄玻璃基板之精密加工。採用一皮秒脈衝雷射系統，此系統可切換1064、532及355奈米三種波長之光源，並以200奈米厚之無鹼玻璃基板作為加工材料。此二步驟製程之第一步驟是改質製程，先以1064奈米波長之紅外線雷射直接照射於無鹼玻璃表面以進行改質，當無鹼玻璃吸收1064奈米雷射光之能量時，其溫度會上升並改變無鹼玻璃之吸光特性，經改質後的無鹼玻璃對於其他波長的雷射光吸收度也會提升。第二步驟是以355奈米波長之紫外線雷射直接照射於改質區域進行加工製程，吸光特性經改質後的區域對於紫外線雷射之吸收度提升後，此雷射加工所需最低能量之閾值會降低，因此可降低使紫外光雷射在改質區加工所需的雷射光功率，使得雷射精密加工較易進行，且可降低熱影響區。雷射照射參數方面，本研究先探討紅外光雷射之輸出功率、脈衝重複率 (Repetition rate)及照射時間對於改質區域生成與否之影響，在所探討之參數範圍內，單一脈衝輸出能量約在60 μJ，並在低重複率(2.5、5、10 kHz)條件下可生成範圍較大之改質區域，而加工時間則較無顯著影響。比較在改質區與非改質區紫外光雷射直接照射之加工結果，發現在非改質區無加工痕跡之加工條件在改質區內則可進行加工，說明了改質區的吸光特性確已改變，此加工變化分別以單點與直線掃描照射探討。最後，將經紅外光雷射改質與未改質之無鹼玻璃進行吸收度量測發現改質後的無鹼玻璃對於355奈米波長之吸收度有些微增加，顯示本製程擁有應用於玻璃微加工之可行性。;This study aims to develop a two-step laser irradiation method for precise machining on thin glass substrate using a picosecond pulsed laser micromachining system. This system is able to switch the picosecond laser to deliver one of the three wavelengths of 1064, 512, or 355 nm. The target substrate is thin alkali-free glass. The first step irradiation is for glass modification that involves irradiating the substrate with the picosecond pulsed beam operating at the wavelength of 1064 nm. The absorbed incident laser energy increases the local temperature of the glass and modifies its light absorptivity, not only for the wavelength of 1064 nm but also for other wavelengths of light. The second step is the precision laser machining, which is accomplished by irradiating the modified area with 355 nm ultraviolet light. Since the absorptivity of the alkali-free glass against UV laser is enhanced after the modification step, the threshold of laser machining on alkali-free glass would be decreased. Hence, the minimum power required for UV laser machining on the modified glass is reduced, thereby making processing easier. In this study, the influence of the three processing parameters, energy per pulse, pulse repetition rate and irradiation time on the machining quality is considered. Results show that a modified area was able to be generated under the processing parameters of energy per pulse of 60 μJ, pulse repetition rates of 2.5, 5, and 10 kHz, respectively. The irradiation time, however, is not that significant. In the step of UV laser machining, by using the same processing parameters on the modified and unmodified areas, the former can be processed, while the later has no effect. The same result can be obtained regardless of whether the machining is processed by single point irradiation or by line scanning. Finally, the absorption measurements on the modified and the unmodified non-alkali glass were conducted. It is found that the modified alkali-free glass has a slight increase in the absorption of the 355 nm wavelength. In summary, this study demonstrates the feasibility of the proposed scheme in laser glass micromachining. |
