Turning Optically Achiral Materials Chiral

In this work, we report on a permanent recording of optical chirality on achiral materials through femtosecond laser-induced periodic surface structures on metals. The experiment uses an amplified Ti:sapphire system that generates 66-fs pulses at a 1-kHz repetition rate with the central wavelength at 800 nm. A zero-order quarter wave plate is used to generate left or right circularly polarized (CP) light, and the laser beam is focused onto a metal surface at different incident angles. To understand this phenomenon, a number of corresponding experimental and theoretical studies are performed, and the results suggest that mirror symmetry of the structures is related to the propagation behavior of excited surface plasmons. It is concluded that these mirror symmetric periodic structures formed from left and right CP light are the only phenomenon that can permanently record light helicity with an optically inactive material.