Tuning optical properties of densified silica glass via high pressure and ultrafast laser excitation

Silica glass exhibits diverse structural configurations accompanied by densification under varying temperature and pressure conditions; these factors significantly influence its optical properties, such as the refractive index. However, the fundamental structural mechanisms underlying the optical properties change induced by high-pressure/high-temperature (HPHT) and femtosecond laser direct writing (FLDW) remain incompletely resolved. Herein, we report the similarities and differences in the optical responses of densified silica glass induced by these two methods. The most significant difference is that the laser-irradiated region evolves toward a glass structure characteristic of a high-fictive temperature (1600–2000 K) by incorporating non-bridging oxygen defects associated with edge-sharing SiO 4 tetrahedra, which induces distinctly different photoluminescence behaviors compared to high-pressure treatment. Our findings demonstrate the ability to locally tailor the glass structure to exhibit unique optical characteristics, thereby enabling the flexible design of optical communication systems and photoelectric fusion devices.