Energy-dependent correlation between micro/nano-morphology and stress state of femtosecond laser-induced modification in fused silica

Due to the importance of stress control in the laser processing of brittle transparent dielectrics such as glass and crystal, investigating the evolution of laser-induced stress state and its manipulation mechanism is highly desirable for ensuring high-performance crack-free laser micro/nanostructuring of dielectrics. Herein, the internal stress state of a femtosecond laser-modified fused silica glass sample at a broad range of pulse energy from 0.34 to 3.5 μJ was evaluated using a cantilever displacement method. Two obvious transition zones in the variation of microscale displacement were identified and analyzed by polarized optical microscopy, scanning electronic microscopy, and confocal micro-Raman spectroscopy. A strong energy-dependent correlation between the evolution of the micro/nano-scale morphology and stress state in laser-induced structures has been investigated and discussed. The analyzed result is beneficial for developing high-efficiency and high-quality manufacturing of 3D large-scale and high-precision glass microstructures.