Mirrors are widely used for redirection of electromagnetic waves in optical systems, making them arguably the most irreplaceable optical component. Metamaterial‐based chiral mirrors, composed of a 2D‐chiral planar metallic structure backed by a conventional mirror, reflect one circular polarization without changing its handedness, while absorbing the other. Here, three types of switchable chiral mirror are demonstrated. Switching from a chiral mirror to either a conventional mirror, a handedness‐preserving mirror, or a chiral mirror of opposite handedness, is realized. These advances are underpinned by switching the handedness of 2D‐chiral metamaterial and the associated effect of circular conversion dichroism, which is reported here for the first time. Switching is achieved by exploiting the temperature‐activated dielectric‐to‐metal phase transition of vanadium dioxide to modify the symmetry and chirality of the metamaterial's resonators. Current distributions explain the temperature‐controlled optical properties by handedness‐selective excitation of reflective electric dipole and absorbing magnetic dipole modes.

Fabry−Peŕot interference plays an important role in modulating the spectral intensity of optical response originating from light−matter interactions. Examples of such interference occurring in the substrate as the resonating cavity have been demonstrated and probed by two-dimensional layered materials. Similarly, the Fabry−Peŕot interference can occur and modulate the optical response in the heterostructure; however, this remains elusive. Herein, we observe the Fabry−Peŕot interference on photoluminescence (PL) and Raman spectra in monolayer WS 2 / SiP 2 heterostructures by varying the thickness of bottom SiP 2 from 2 to 193 nm, which serves as the Fabry−Peŕot cavity. Both the intensities of the PL spectra and the E 2g1 Raman mode of WS 2 /SiP 2 heterostructures first decrease to almost zero while displaying an interference increase at a SiP 2 thickness of 75 nm. Our findings clearly demonstrate the Fabry−Peŕot interference in the optical response of heterostructures, providing crucial information to optimize the optical response and paving the way toward photodetector applications.

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