Enhancing Circularly Polarized Emission by a Planar Chiral Dielectric Metasurface

Circularly polarized emission (CPE) has attracted great interest in optoelectronics, biosensing, etc. Here, a resonant planar chiral dielectric metasurface that can be constructed to provide a preferable way for CPE is demonstrated. The planar metasurface is easy to fabricate, and the corresponding far-field circular polarization degree is extremely high and angle-insensitive. The designed metasurface is made of a periodic array of in-plane mirror-asymmetric silicon pillar dimers and supports a low-leakage chiral band-edge mode. Experimentally, the photoluminescence of a thin film of PbS/CdS quantum dots coated on such a metasurface is enhanced by 57 times with the far-field degree of circular polarization as high as 0.74. The planar platform provides a flexible and efficient way for manipulating CPE, in which other periodic coupling effects may also be adopted to enhance the light-matter interaction, such as quasi-bound states in the continuum and lattice resonance.