Femtosecond laser pulses focused inside transparent materials modify their optical properties that are used in many applications ranging from waveguide and microfluidic fabrication to biomedicine. In this work, it has been demonstrated that using two laser pulses separated in time from hundreds of femtoseconds to several picoseconds provides much better control over modification than single pulses, opening new prospects for laser-induced three-dimensional structuring inside glasses.
(a) Experimental data on the transmission microscope signal (TMS) for the case of irradiation of fused silica in its volume by double pulses at a wavelength of 800 nm as a function of time delay between two pulses (accumulation of 5, 10, 20, and 50 and double pulses). The energies of two pulses and their sequence are shown on top. Zero-time delay corresponds to the single pulse action. The pink line corresponds to numerical calculations supporting the experiment. (b) The spatial distribution of the absorbed laser energy obtained numerically for the experimental conditions demonstrating highly localized energy deposition that is in good agreement with the experiments.