The formation process of self-organized nanograting in fused silica glass with femtosecond laser (1 kHz, 120 fs, 800 nm) double-pulse sequences irradiation is investigated by combined control of polarization state of individual pulse, interpulse temporal delay (from  −330 to 350 ps) and energy ratio in each sequence. It is found that the as-formed nanograting induced by the first pulse can be erased by the second pulse in repeated sequences irradiation, and moreover a new one is be rewritten in situ if the two pulses in a sequence were temporally well separated. The rewritten nanograting shows a new orientation perpendicular to the polarization direction of the second pulse. Additionally, the erasing and rewriting of nanograting can become more efficient as long as the second pulse energy increases to be higher than the first one, regardless of the interpulse delay. Our result shows that the energy ratio in double-pulse sequences plays a decisive role in the erasing and rewriting, because formation of nanograting mainly depends on the pulse energy deposition process. This study provides a useful reference for application of high-density data storage and amendment of nanograting.

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In this paper, we theoretically studied the propagation of the first-order spatiotemporal coupled ultrafast pulse in fused silica glass by using the Cartesian nonlinear Schrödinger equation coupled with the electron density rate equation. We found that wavefront rotation, one parameter of the shaped pulse, may play an integral role to adjust the asymmetrical modification under different initial coupling conditions. During the focusing process, the pulse wavefront generates or rotates the pulse front through angular dispersion, and this process directly causes the change of inclined direction of the pulse front tilt at the focal plane. The spatiotemporal coupling change could make a difference in the asymmetric distributions of intensity, fluence, and electron density at the plane of interaction, and further affect the photoionization process. Therefore, the research on the influence of wavefront rotation on the pulse front tilt under the initial pulse incidence condition helps us to understand the temporal and spatial evolution of ultrafast laser pulses. Based on our numerical simulation, the possible mechanism of nonreciprocal direct-writing phenomena is revisited by taking into account the effect of wavefront rotation.

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