For Scientific Research & Industry Modernisation.
Glass is a transparent solid-like material that is widely used in people’s daily lives. The range of applications for glass is expanding, especially in combination with other materials for more high-tech applications. Made from common materials such as sodium carbonate, limestone and sand, glass has unique properties not found in other materials. It has excellent optical properties, reflecting, bending, transmitting and absorbing light with high transparency throughout the visible range and beyond. In terms of physical properties, glass has a hard surface, is scratch and wear resistant, and in recent years, through various methods, it has even become elastic. However, it is also these properties that make glass fabrication more challenging, such as becoming fragile once the glass has excellent tensile strength.
Normally a small crack is all that is needed to cause the glass to break. Once a microcrack forms in one part of the glass, it can spread to the edge of the glass and cause breakage. This fragile property of glass makes it difficult to work with.
This solution uses a femtosecond laser to process glass by using femtosecond pulses that are tightly focused on the surface of the glass with a power density of more than several terawatts per square centimeter, triggering complex and diverse processes such as simultaneous multiphoton absorption, avalanche and collisional ionization, resulting in highly localized damage to the glass substrate with virtually no energy deposition. Due to the extremely short pulses of the femtosecond laser, the thermal impact is negligible and therefore the process can be called “cold processing”. It does not cause cracks that could lead to glass breakage.
Fig. 1. Parallel lines and lattice structures with a period of 1 μm fabricated in glass by femtosecond laser
In the meantime, using femtosecond laser focused by a high numerical aperture lens can yield high-resolution structure. As shown in Fig 1, where the structure with a spacing of 1 μm is visible, the processed parallel lines can be clearly distinguished. During the process, the femtosecond laser results in a permanent morphological change in the glass, instead of a refractive index change. This is exactly what is expected in order to form components on the glass at a later stage.
Femtosecond laser microfabrication of transparent materials has unique advantages compared to other microfabrication techniques. Due to the nonlinear absorption mechanism, the laser-induced variant is confined to the focused volume, allowing geometrically difficult structures to be realized. In addition, femtosecond laser material processing is highly accurate because the seed electrons causing the absorption effect are generated by nonlinear ionization and do not require defective electrons. Due to the reproducibility and limitations of nonlinear excitation, femtosecond laser microfabrication can be used for practical purposes.
It can be widely used in glass surface structure engraving, glass surface grating production, glass phase plate production, glass holographic optical element production and glass surface modification.