Femtosecond laser induced migration of alkali ions in calcium silicate glasses

We report on an abnormal migration phenomenon of alkali ions in calcium silicate glasses, induced by 250 kHz, 800 nm femtosecond laser irradiation. The diameter of the laser-affected zone is not dependent on the glass-transition temperature of glass samples. Elemental analysis by Electro-Probe Microanalyzer demonstrates that K ions migrate to the periphery of the laser-affected zone, while Cs ions show an opposite tendency in the two alkali ions coexisting glass. The possible mechanism on the observed abnormal phenomenon is discussed.