Temporally chirped femtosecond pulse laser non-reciprocal writing on the silicon

In this paper, a non-reciprocal writing effect is proposed on the silicon by a femtosecond laser with tailor of temporal chirp. The induced structures which belong to the written lines with two opposite scans show obvious difference in the ablated regions. The grating compressor of a laser system is controlled to change the temporal chirp so as to flip the direction of the pulse front tilt, which results in 2 types of induced structures exchanging between two opposite scans. We assume, during the laser scans along the pulse front tilt, there may have a snowplow effect on the excited free electrons, leading to an asymmetrical electrical field distribution around the focal area. This process could further boost an ionization efficiency in the next pulse irradiation as well as make the induced structures grow faster. Current result possibly offers a new route to control the density of free electrons excited when femtosecond laser interacts with silicon wafer.