Ultrafast Laser For Glass Processing

The special properties of glass make glass processing face greater challenges. What breakthroughs will the application of ultrafast lasers bring? Glass is a transparent solid-like material with unique properties not found in other materials:

The laser pointer has excellent optical properties, can reflect, bend, transmit and absorb light, and has a higher transparency in the entire visible range and even farther; from the perspective of chemical properties, glass is an inert against corrosion. Materials can be used as containers for many chemicals. From a thermal and electrical perspective, glass is an excellent insulator. From the perspective of physical properties, the glass surface is hard, scratch-resistant and wear-resistant. In recent years, glass has even been elastic through various methods. However, it is precisely these properties that make glass processing face greater challenges. For example, once glass has excellent tensile strength, it becomes brittle.

Glass is widely used in people’s daily life, and its application scope is constantly expanding, especially in combination with other materials, it can be more used in the green laser pointer high-tech field. Glass is made from common materials such as sodium carbonate, limestone and sand. These materials melt at high temperatures (about 1500 ° C) and, like liquids, can be poured, blown, pressed, and molded into various shapes. However, at room temperature, glass becomes a solid, and it becomes difficult to process it after cooling due to changes in mechanical properties.

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Therefore, the method of processing glass and its application need to be considered in the long run. Glass manufacturing dates back to around 3500 BC. Artificial glass probably appeared first in Mesopotamia and Egypt. It was first used to make jewelry and then used to make pots. Since then, the processing technology has continued to improve, from manual processing to today’s high-tech industrial processes, and many glass categories and applications have emerged. Although glass manufacturing has a long history, in recent decades, due to the fragile properties of glass, the processing of glass products has stopped.

Usually a small crack causes the glass to break. Once a microcrack is formed in some part of the glass, it will spread to the edge of the glass and cause cracking. This fragile nature of glass makes it difficult to process. On the other hand, evolving technology has made it possible to make glass with smaller structures and different shapes for use in different fields. Traditional precision methods, such as photolithography and electron beam lithography, are used to process glass, but these technologies are too expensive and difficult to operate, especially for large areas. Today, laser technology provides the most accurate method of processing glass. The most straightforward method is to use single photon absorption in the wavelength range, and glass is not highly transparent under infrared or ultraviolet rays.

However, Laser Engraver‘s direct absorption can cause some problems, including adverse thermal effects and the formation of heat affected zones, which can cause microcracks and seriously endanger the mechanical stability of glass. In addition, processing below the glass surface to make three-dimensional structures requires the use of highly transparent wavelengths. Although nanosecond pulse lasers can be used to make subsurface structures in glass (see Figure 1), the physical mechanism of glass can limit the fineness of microprocessing, and microcracks can occur.

In recent years, an exciting alternative process has been put into industrial use, which uses ultrafast lasers to generate sub-picosecond pulses in the near-infrared wavelength range. In this method, ultra-short pulses are closely focused on most of the glass or surface, and the power density per square centimeter is more than a few terawatts, which triggers complex and diverse processes such as simultaneous multiphoton absorption, avalanche, and impact ionization, causing glass damage to the glass. The matrix is ​​highly localized and there is almost no energy deposition (only a few microjoules or less). Due to the extremely modest amount of energy used for each pulse, the thermal impact on the area (even the focus volume) is negligible. This method is often referred to as “cold ablation” and can be used to make extremely accurate 3D structures. Compared with other microfabrication technologies, femtosecond laser microfabrication has unique advantages.