An Angle- and Polarization-Selective Dual-Wavelength Narrowband Thermal Emitter for Infrared Multilevel Encryption

The explosive growth of data has intensified challenges to information security, spurring a critical need for advanced encryption technologies, and relying solely on digital encryption still leaves information vulnerable to interception and leakage during transmission. Therefore, encryption technologies that combine digital algorithms with physical keys to further enhance information security are widely studied. In this work, we present an angle- and polarization-selective dual-wavelength long-wavelength infrared narrowband thermal emitter for infrared encryption-decryption applications. The thermal emitter is composed of an epsilon-near-zero material upon a metallic layer, designed to enable the excitation of the Berreman mode and asymmetric Fabry-Pérot resonance simultaneously. Numerical simulations combined with the transfer matrix method are employed to analytically investigate the optical responses, demonstrating good agreement with experimental results. Moreover, a robust multilevel cryptographic communication system is developed, utilizing the thermal emitter's imaging results as the physical-layer key to enable highly efficient information encryption and decryption. We anticipate that the proposed thermal emitters will pave the way for realizing relevant applications in various information encryption devices.