Secret hologram key with angular multiplexing based on PDLC photonic crystals using Morse code matrices

Morse code, as a well-known digital communication method, not only revolutionized information transmission throughout history but also continues to serve modern specialized communication needs. By using modern optical technologies to embed Morse code, the unique characteristics of the code can be leveraged to achieve more secure encryption. Therefore, a secret hologram key based on polymer dispersed liquid crystal photonic crystals (PDLC-PCs) is proposed to compose a sequence of enciphered messages using matrix Morse code. This hologram key is fabricated by multipass holographic interference with different information in each light channel. During the decoding process, we use a series of reconstruction orders under various diffraction angles to obtain several dynamic digit matrices. These different digit matrices can provide Morse code for code words according to the holographic conjugate images. From this, we can identify the corresponding Morse code based on the ciphertext and thereby decipher the plaintext message. This method can help us hide the actual elements required for the combined secret information within the hologram key, allowing for the dynamic combination of confidential information as needed.