Tailored excitation sequences for optimized laser-induced modifications in bulk transparent materials exposed to sub-ps irradiation

Tight focusing of ultrashort near infrared laser pulses in the bulk of various transparent materials induces significant modifications of the optical properties by locally changing the material refractive index. Such laser-induced phase objects are of major technological interest, notably for direct writing of embedded optical functions. While extensive studies have been reported on ultrashort pulsed laser induced modifications in several materials, especially with regard to focusing conditions, incubation effects, or the influence of the energy content of the pulse, we emphasize here the role of the temporal design of the excitation sequence. We present phase-contrast microscopy investigations of the resultant morphology and discuss the refractive index topological map induced by different temporal pulse intensity envelopes in various transparent materials. The consequences of temporal profiles generated by a pulse shaping apparatus on the morphology of the interaction zone are illustrated, emphasizing the benefits of the synchronization between the excitation temporal profile and the material response.