A powerful technique for recording and reconstructing complete information about the optical field, including intensity and phase, is optical holography. Numerous fields, including optical display, imaging, data storage, encryption, and metrology, have utilized it extensively. The need for more coding freedom to meet high-security and high-capacity challenges has become apparent with the rapid growth of the information society.
In holographic systems, independent information channels based on the physical dimensions of light, such as wavelength, angle of incidence, polarization, and time, are possible; however, spatial channels are not widely available. In the orbital angular momentum (OAM) dimension of light, researchers have discovered new opportunities for multiplexed holography after exhausting the physical dimensions that are available.
By testing visualizations suitably in energy space, scientists have executed OAM as a free data transporter for optical holography, prompting OAM multiplexed holography. OAM’s inherent orthogonality and infinite spiral modes make this method capable of optical information processing like no other.
“The MHC-OAM multiplexed holography generic design approach can be extended to achieve holographic multiplexing in higher dimensions, such as by combining light polarization and wavelength. This offers up new avenues for improving information capacity and security in optical holography.”
Prof. Xiao Yuan, principal investigator at Soochow University’s Key Laboratory of Advanced Optical Manufacturing Technologies,
A novel strategy known as multiramp helical conical OAM (MHC-OAM) was recently proposed by researchers from Soochow University in China to further enhance holographic multiplexing. As revealed in Cutting Edge Photonics Nexus, this approach utilizes a spatial light modulator (SLM) to accomplish MHC radiates with various boundaries that can act as data encryption or unscrambling channels, fundamentally extending the capacity of holographic multiplexing.
The design permits various types of MHC-OAM holography and spatially arbitrary MHC beam waveforms by relying on independently modulated MHC beam parameters. Three additional parameters, in addition to the topological charge provided by OAM, can act as carriers for information encoding and decoding: the normalized factor, the constant of the MHC beam, and the quantity of mixed screw-edge dislocations across multiple ramps.
Higher-dimensional holographic multiplexing can be achieved by combining the four parameters of the MHC beam in a different way, which can improve security.
Advanced nested optical encryption platforms can now be created thanks to the multidimensional MHC-OAM hologram’s supply of additional security keys. This development reforms existing optical encryption plans with restricted information limits or low security. The encoded data becomes immune to certain brute-force attacks when MHC-OAM holograms are used to encrypt and decrypt optical information based on particular MHC modes.
To meet the growing demand for parallel, high-security information transmission, the optical encryption scheme theoretically provides unlimited information channels.
“The generic design approach of MHC-OAM multiplexed holography can be extended to achieve holographic multiplexing in higher dimensions, such as by combining the polarization and wavelength of light,” claims Prof. Xiao Yuan, principal investigator at Soochow University’s Key Laboratory of Advanced Optical Manufacturing Technologies. This opens additional opportunities for upgrading data limits and security in optical holography.”
With the potential for limitless data channels and impenetrable encryption, optical holography proceeds to develop and fulfill the needs of the data age.
More information: Nian Zhang et al, Multiparameter encrypted orbital angular momentum multiplexed holography based on multiramp helicoconical beams, Advanced Photonics Nexus (2023). DOI: 10.1117/1.APN.2.3.036013
