Brittle materials such as quartz glass have excellent physical and chemical properties and exhibit excellent high-temperature resistance, corrosion resistance, and electrical insulation. Consequently, they are widely used in the aerospace industry, laser weapons, optical systems, and consumer electronics. In the aerospace field, quartz glass is often used to prepare sensitive components for high-temperature pressure sensors, accelerometers, and resonators. In the preparation of microelectromechanical system (MEMS) sensors, high-precision and high-quality structural processing is the key to ensuring excellent sensor performance. The high hardness and brittleness of quartz glass result in various defects when traditional mechanical and chemical processing methods are used. Recently, scholars have conducted a series of studies based on laser processing technology. Femtosecond lasers have the characteristics of ultrahigh-peak intensity and high-repetition frequency, which can directly ionize materials in the affected area to achieve non-thermal melting “cold processing” and remove the material at the microscale level. Femtosecond lasers offer advantages in terms of ultrafine and low-damage characteristics, unmatched by long-pulse lasers. Therefore, femtosecond lasers are optimal for extreme manufacturing across various fields. However, because of the limitation of the Rayleigh length of Gaussian beams, femtosecond lasers result in defects such as chips, microcracks, and surface deposition on the cutting surface during microstructural processing. Femtosecond laser filament processing is expected because of its high precision and quality. Most of current reports on optical filament processing are focused on larger wafer-cutting processes, whereas there are few reports on ultraviolet-laser optical filament processing technology, which has advantages in micro/nano precision machining. The ultraviolet lasers has a lower threshold for material damage, and the fine filaments generated by laser self-focusing result in higher processing accuracy. This study uses the controlled variable method to analyze the influence of different laser pulse energies, repetition frequencies, scanning speeds, and scanning times on the morphology of quartz glass optical filament damage. Our goal is to improve the cutting accuracy of femtosecond lasers on quartz glass and apply femtosecond laser filament processing technology to the preparation of micropores. Ultraviolet femtosecond laser filament processing provides a new approach for the high-precision processing of hard and brittle materials.

The thickness of the quartz glass was 200 μm, and the quartz glass was ultrasonically cleaned in an alcohol solution to remove surface impurities before the experiment. By maintaining the laser pulse energy greater than the self-focusing threshold, the influences of the laser focus position, laser pulse energy, repetition frequency, laser scanning speed, and scanning times on the damaged quartz morphology were investigated. The processed quartz glass was cleaned, and the damage morphology of the processed section was analyzed using scanning electron microscopy and laser confocal microscopy. Based on the experimental results, appropriate laser parameters were selected for the rapid cutting of quartz glass, and a detailed comparison was conducted with the morphology of traditional progressive laser scanning processing. The laser processing parameters were optimized for the microporous processing of quartz glass and compared with those of the conventional laser drilling method.

After processing quartz glass using a 343 nm ultraviolet femtosecond filament, the filamentary damage formed inside is fine and straight. It is more likely to cause deeper damage inside the quartz glass when the femtosecond laser is focused on its surface (Fig.4). The higher the pulse energy and repetition frequency of the femtosecond laser, the deeper the damage to the quartz glass by the laser filament. Chipping can be effectively avoided by processing at laser frequencies of 100 kHz and 200 kHz (Fig.5). A scanning speed of 10 mm/s ensures the quality and efficiency of the optical filament processing. Increasing the number of scans can effectively improve processing quality and depth. Cutting quartz glass using the optimal parameters yields a smooth cut surface profile with no visible chipping. The internal damage width of the quartz glass is approximately 1 μm (Fig.9), and the roughness of the cut surface is 0.56 μm (Fig.10). This method is suitable for the high-precision cutting of transparent and brittle materials. The accuracy of microporous processing in thin quartz glass using femtosecond laser filaments is ±1 μm, which is a significant improvement compared to that of the conventional laser progressive scanning method (Fig.11).

In this study, based on the filament effect generated by femtosecond laser self-focusing, ultraviolet femtosecond laser filamentation is used to process quartz glass, and the influence laws of different laser parameters on the processing morphology are derived. Quartz glass is rapidly cut and microporously processed with optimized process parameters. The results show that the quartz glass and microporous holes processed using this method have higher quality and precision, providing a new reference for the precision processing of microdevices. This method offers unique advantages and application prospects in laser processing.