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Sean Rodrigues1 Lei Kang2 Mohammad Taghinejad1 Shoufeng Lan1 Kyutae Lee1 Augustine Urbas3 Wenshan Cai1

1, Georgia Inst of Technology, Atlanta, Georgia, United States
2, The Pennsylvania State University, University Park, Pennsylvania, United States
3, Air Force Research Laboratory (AFRL), Dayton, Ohio, United States

Simple metallic mirrors flip the spin of a circularly polarized wave upon normal incidence by inverting the direction of the propagation vector. Altering or maintaining the spin and polarization of waves carrying data is a critical need to be met at the brink of photonic information processing. In this work, we report a chiral metamaterial mirror that strongly absorbs a circularly polarized wave of one spin state and reflects that of the opposite spin in a manner conserving the circular polarization. A circular dichroic response in reflection as large as ~0.5 is experimentally observed in a near infrared wavelength band. By imaging a fabricated pattern composed of the enantiomeric unit cells, we directly visualize the two key features of our engineered meta-mirrors, namely the chiral-selective absorption and the polarization preservation upon reflection. Beyond the linear regime, the chiral resonances enhance light-matter interaction under circularly polarized excitation, greatly boosting the ability of the metamaterial to perform chiral-selective signal generation and optical imaging in the nonlinear regime. Chiral meta-mirrors, exhibiting giant chiroptical responses and spin-selective near field enhancement, hold great promise for applications in polarization sensitive electro-optical information processing and biosensing.

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