Uniformly locally chiral light for global control of chiral light-matter interaction

Locally chiral light (LCL) is a promising tool for probing and controlling molecular chirality. The pioneering tricolor LCLs' degrees of chirality (DOCs) change periodically in space and vanish by integrating over the whole spatial period, making them cease to be globally effective (i.e., globally achiral). Locally and globally chiral light (LGCL) is a type of more efficient LCL whose DOCs survive by integrating but still change periodically in space. Here, we propose a scheme to generate a new type of LCL called uniformly locally chiral light (ULCL). ULCLs are globally chiral and have spatially uniform DOCs, which makes them superior to current types of LCLs in studies of chiral molecules. By applying the ULCLs in an optical molecular-chirality switch, the racemic mixtures can be converted to enantiopure samples without size restrictions, where the perfect control of molecular chirality with a global efficiency of $100\%$ is predicted, which is twice that of LGCLs. Our work potentially constitutes the starting point for developing more efficient chiroptical techniques for probing and controlling molecular chirality.