  Domain wall displacement in Co/Pt thin films induced by not only fs- but also
ps-laser pulses is demonstrated using time-resolved magneto-optical Faraday
imaging. We evidence multi-pulse helicity-dependent laser-induced domain wall
motion in all-optical switchable Co/Pt multilayers with a laser energy below
the switching threshold. Domain wall displacement of about 2 nm per 2- ps pulse
is achieved. By investigating separately the effect of linear and circular
polarization, we reveal that laser-induced domain wall motion results from a
complex interplay between pinning, temperature gradient and helicity effect.
Then, we explore the microscopic origin of the helicity effect acting on the
domain wall. These experimental results enhance the understanding of the
mechanism of all-optical switching in ultra-thin ferromagnetic films.
