  The notion of chiral-induced spin selectivity (CISS) has attracted intensive
research interest recently. However, the practical applications of the CISS
effects face challenges due to relatively low spin polarization. In this
Letter, we propose a non-perturbative theory illustrating how circularly
polarized (CP) light enhances CISS effects through strong light-matter
interactions. We introduce a Floquet electronic friction model to study the
nonadiabatic dynamics and spin transport through a chiral molecule in a
molecule junction subjected to external driving. Our results show that the
interplay of the nonadiabatic effects and light-matter interactions can
significantly ($>90\%$) enhance electron spin polarization under CP light. Our
predictions can be very useful in experiments for using CP light to control
spin current in chiral molecular junctions.
