Efficient Nanostructuring in Silica Glass With Ultrashort Laser Pulses Down to 10 Fs

So far, most studies on ultrafast laser writing have been conducted with pulses longer than 40 fs [1], where free electrons are generated through multiphoton ionization (MPI) and/or tunneling ionization (TI), followed by avalanche ionization [2]. Although densification has been demonstrated in silica glass using 27 fs [3] and 7 fs pulses [4], the interaction between few-cycle pulses and transparent materials remains insufficiently explored. Here, we investigate the impact of pulse duration, ranging from 300 fs down to 10 fs, on the formation of birefringent voxels for application in optical data storage. Compared to 300 fs pulses, 10 fs pulses can induce birefringent voxels with larger retardance and smaller slow axis azimuth error at the same energy. This enhancement could be attributed to a more efficient near-field enhancement mechanism [5] enabled by the higher intensity of shorter pulses.