Ciliary white light generated during femtosecond laser ablation on transparent dielectrics

Intense laser pulses impinged on the surface of solid dielectrics lead to ablation, massive material removal from the surface. With femtosecond laser pulses, many interesting phenomena have been observed during this process, such as surface periodic fringe with period much less than the laser wavelength (0.1λ~0.5λ), formation of arrays of nanometer-scale rods, etc. So far, little attention has been given to the evolution of the laser pulse itself during the ablation process. Here we present the first experimental investigation on the spatial and spectral evolution of femtosecond laser pulse during laser ablation of transparent materials. A universal new phenomenon, coined as ciliary white-light was observed, which also provides a real time in-situ observation of laser ablation on transparent materials.