Transient and selective laser (TSL) processing rapidly and precisely removes material from aluminosilicate glass and other transparent materials. This method simultaneously irradiates glass with an ultrashort-pulse laser, which excites electrons, as well as a low intensity long-pulse laser. The region of excited electrons absorbs the long-pulse laser, which removes material and microfabricates the glass.

However, the mechanism of material removal via TSL processing is unclear. Yoshizaki et al. determined what factors control this process. They measured the TSL processing threshold of synthetic fused silica, a material with a low concentration of impurities.

The authors found the relationship between the intensity of the long-pulse laser and the density of excited electrons represented the processing threshold, suggesting these are the controlling factors of material removal.

“Our work is important, because we clearly showed the strong relationship between the transient absorption of low intensity laser and the density of excited electrons,” said author Reina Yoshizaki. “Understanding the transient absorption phenomena will advance not only the material processing field but also condensed matter physics.”

The authors believe understanding the mechanism of TSL will help better control the shape of materials during microfabrication. They were able to use their findings in this work to enhance the processing efficiency for fused silica and hope it could be used to increase efficiency for other materials.

This work showed transient absorption continues for more than 1 microsecond during TSL processing. Next, the authors will study the mechanism of long transient absorption, which is still not understood.

Source: “Mechanism of material removal through transient and selective laser absorption into excited electrons in fused silica,” by Reina Yoshizaki, Yusuke Ito, Shunya Yoshitake, Chaoran Wei, Akihiro Shibata, Ikuo Nagasawa, Keisuke Nagato, and Naohiko Sugita, Journal of Applied Physics (2021). The article can be accessed at