Optical scanning cryptography system based on Light Spring

Optical scanning cryptography (OSC) has garnered considerable attention because of its ability to acquire an incoherent hologram from a physical object using a single-pixel sensor. In this paper, we generate a new type of scanning pattern, named light spring (LS), using the two-pupil optical heterodyne scanning system. The light spring, which is characterized by helical structures for their phase and intensity profiles, can be built on the superposition of two distinct laser frequency components. An optical scanning cryptography scheme based on LS is proposed. The scheme expands the temporal characteristics of orbital angular momentum (OAM) multiplexing and improves the encryption capability, key space and security of the system.