Four‐Channel Amplitude‐Phase‐Janus‐Encrypted Acoustic Meta‐Hologram

ABSTRACT Conventional encrypted optical and acoustic meta‐holograms only focus on the encrypted hologram in amplitude channel, viz. modulating spatial amplitude to encrypt or project a holographic image, which may lead to information leakage in other channels. In this research, the unique concept of four‐channel amplitude‐phase‐Janus‐encrypted acoustic meta‐holograms is proposed, demonstrating remarkable capabilities of generating, encrypting, and decrypting both amplitude and phase holographic images on both sides of a metascreen. The flexible and decoupled manipulation mechanism for the amplitude‐phase of the bidirectional acoustic waves used in our concept offers multiple possibilities to apply unconventional amplitude‐phase‐encryption methods. In this work, our system enables single‐input, two‐faced four‐channel encryption, which substantially increase the communication capacity of conventional acoustic holograms, and the security of amplitude‐phase‐encryption is demonstrated. Our work can lead to concrete applications including multi‐channel acoustic field communications with high security framework, acoustic illusion and cloaking in non‐transparent media, etc.