Ultrafast internal modification of glass by selective absorption of a continuous-wave laser into excited electrons.

The internal modification of glass using ultrashort pulse lasers has been attracting attention in a wide range of applications. However, the remarkably low processing speed has impeded its use in the industry. In this study, we achieved ultrafast internal modification of glass by coaxially focusing a single-pulse femtosecond laser and continuous-wave (CW) laser with the wavelength that is transparent to the glass. Compared with the conventional method, the processing speed increased by a factor of 500. The observation of high-speed phenomena revealed that the CW laser was absorbed by the seed electrons that were generated by the femtosecond laser pulse. This technique may help expand the applications of femtosecond lasers in the industry.