  All-optical helicity dependent switching (AO-HDS), deterministic control of
magnetization by circularly polarized laser pulses, allows to efficiently
manipulate spins without the need of a magnetic field. However, AO-HDS in
ferromagnetic metals so far requires many laser pulses for fully switching
their magnetic states. Using a combination of a short, 90-fs linearly polarized
pulse and a subsequent longer, 3-ps circularly polarized pulse, we demonstrate
that the number of pulses for full magnetization reversal can be reduced to 4
pulse pairs in a single stack of Pt/Co/Pt. The obtained results suggest that
the dual-pulse approach is a potential route towards realizing efficient AO-HDS
in ferromagnetic metals.
