| dc.description.abstract | 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. | en_US |