Microscopic bulk damage in dielectric materials using nanojoule femtosecond laser pulses

Summary form only given. We tightly focus femtosecond laser pulses in the bulk of a transparent material. The high intensity at the focus causes nonlinear absorption of the laser energy, producing a microscopic plasma and damages the material. In previous work, we examined the morphology of such material damage and measured the dynamics of the plasma expansion. Here we report the thresholds for bulk damage and critical self focusing in fused silica using 110-fs pulses at both 400-nm and 800-nm wavelength. We find that permanent damage can be produced with energies of only tens of nanojoules. In addition, we observe no significant self-focusing at these energies.