Crack Propagation in a Ruby Single Crystal by Femtosecond Laser Irradiation.

We have investigated the deformation mechanism of ruby in a microscopic area using a femtosecond laser having a pulse width, wavelength, and repetition rate of 238 fs, 780 nm, and 1 kHz, respectively. Transmission electron microscope observation revealed that a specific oblique pattern originating from cracks having a width of approximately 10 nm formed at the focal point. The peak shift of ruby fluorescence indicated the existence of a residual stress of 0.11 GPa at the irradiated area. Considering the pattern and magnitude of the residual stress at the focal point, we suggest that the crack propagated along the rhombohedral planes and the planes by laser irradiation. [ABSTRACT FROM AUTHOR]