Extrinsically 2D-Chiral Metamirror in Near-Infrared Region

Many previously observed strong chiroptical effects are limited to chiral metamaterials with complex three-dimensional building blocks. Recently, chiral metamirrors consisting of planar elements are proposed to selectively reflect one particular circularly polarized light (CPL) while absorbing the other, with the reflected one either preserving or altering its spin state. However, they are limited by complicated subwavelength chiral profiles of their unit cells, which are challenging to fabricate in the visible-near infrared (NIR) region. We present an extrinsically 2D-chiral metamirror that reflects one CPL preserving its handedness while strongly absorbing the other, reaching a circular conversion dichroism (CCD) in reflectance as large as 0.43 in the NIR region. Our polarisation-conserving mirror possesses an Au pillar array and a continuous Al film separated by a SiO2 dielectric layer, where the Au pillars are periodically arranged by a rectangular lattice. The rather simple geometry of mirror signifi...