Enantiomer‐Selective Molecular Sensing in the Nonlinear Optical Regime via Upconverting Chiral Metamaterials

Enantiomers are chiral isomers in which the isomer's structure itself and its mirror image cannot be superimposed on each other. Enantiomer selective sensing is critical as enantiomers exhibit distinct functionalities to their mirror image. Discriminating between enantiomers by optical methods has been widely used as these techniques provide nondestructive characterization, however, they are constrained by the intrinsically small chirality of the molecules. Here, a method to effectively discriminate chiral analytes in the nonlinear regime is demonstrated, which is facilitated by an upconverting chiral plasmonic metamaterial. The different handedness of the chiral molecules interacts with the chiral metamaterial platform, which leads to a change in the circular dichroism of the chiral metamaterial in the near‐infrared region. The contrast of the circular dichroism is identified by the upconverted signal in the visible region. A nonlinear optical scheme is developed to effectively discriminate chiral analytes, facilitated by an upconverting chiral plasmonic metamaterial. The different handedness of chiral molecules interacts with the metamaterial platform, leading to a change in the circular dichroism in the near‐infrared region. The contrast of the circular dichroism is further transduced into upconverted emission signals in the visible spectrum.