  Based on the four-level double-$\Delta$ model composed of two degenerated
(left- and right-handed) chiral ground states and two achiral excited states,
we propose a purely optical method for enantio-conversion of chiral mixture. By
choosing appropriate parameters, the original four-level model will be
simplified to two effective two-level sub-systems with each of them involving
one chiral ground state. Then, with the help of well-designed optical
operations, the initial unwanted and wanted chiral ground states are converted,
respectively, to the wanted chiral ground state and an auxiliary chiral excited
state with the wanted chirality, i.e., achieving the enantioconversion of the
chiral mixture. Comparing with the original work of enantioconversion based on
the four-level double-$\Delta$ model with the requirement of the time-consuming
relaxation step and repeated operations, our method can be three orders of
magnitude faster since we use only purely optical operations. Thus, it offers a
promising candidate for fast enantioconversion when the total operation time is
limited due to the racemization and/or experimental conditions.
