Wavelength‐Dependent Chiroptical Reversal in Resonant Metasurface Photothermoelectric Photodetector for Dual‐Mode Encrypted Communication

Multidimensional optical encoding using wavelength and polarization offers an attractive route toward secure and high‐capacity optical communication, yet conventional photodetectors generally lack the ability to directly resolve multiple optical degrees of freedom. Herein, we demonstrate wavelength‐dependent chiroptical reversal in a self‐powered photothermoelectric circularly polarized photodetector based on a resonant Z‐shaped Au chiral metasurface/MoS 2 heterostructure, enabling electrical decoding of wavelength‐helicity jointly encoded optical states. The chiral metasurface supports gap‐surface plasmon resonances that enhance helicity‐dependent infrared absorption, generating localized photothermal heating and electrical output driven by the temperature gradient in the MoS 2 channel. Notably, the device exhibits wavelength‐dependent chiroptical reversal, showing opposite helicity preferences at 1064 and 1310 nm with photocurrent asymmetry factors of 0.84 and −0.66, respectively. Near‐field distribution and multipole decomposition reveal that the reversal originates from wavelength‐selective mode switching, involving a magnetic quadrupole resonance at shorter wavelengths and a magnetic dipole resonance at longer wavelengths. By integrating enantiomeric metasurface regions into a dual‐channel architecture, we directly discriminate wavelength‐helicity jointly encoded four logic states (00, 01, 10, and 11), enabling hardware‐level optical decoding. This work unveils the wavelength‐dependent chiroptical reversal mechanism in chiral metasurface heterostructures and provides a promising platform for hardware‐level multidimensional decoding toward encrypted optical communication.