Pulsed laser modification of transparent dielectrics: what can be foreseen and predicted by numerical simulations?

Numerical simulations based on Maxwell's equations have been performed for gaining deep insight into the processes governing laser light absorption in transparent dielectrics in the regimes typical for laser direct writing of various optical structures inside bulk glasses such as waveguides, nanoplanes, and voids. Numerical simulations have been performed for fused silica glass irradiated by femtosecond laser pulses at 800 nm wavelength. The geometry of laser energy absorption is compared for two pulse durations and energies from 0.1 to 1 mu J. The effect of the numerical aperture of the laser energy deposition is studied. Double-pulse irradiation has been modeled to gain insight into exciton-seeded multiphoton ionization [Phys. Rev. B 81, 212301 (2010).]. Furthermore, several consecutive laser pulses have been modeled to gain a better understanding of the qualitative tendency of memory effects related to defect accumulation. Features of laser energy coupling into bulk glass such as asymmetry of absorption for the cylindrically symmetric linearly polarized beam and formation of a defect shield developing in multipulse irradiation regimes have been revealed. (C) 2014 Optical Society of America