Iterative data reconstruction in a thin photonic data storage medium using three-dimensional (3D) absorbers in a highly scattering medium is presented for secure data storage. 3D absorbers are used as data. A highly scattering medium protects data to measure 3D absorbers without knowledge of the scattering coefficient distribution because the phase information is lost during multiple scattering. This prevents an interferometer from measuring the volume medium. To recover the 3D absorbers, a 3D scattering coefficient distribution model is used as prior information and then an iterative method is applied to reduce the difference between the measured and numerical output intensity distributions. A preliminary numerical evaluation is presented.
Iterative data reconstruction in a thin photonic data storage medium using three-dimensional (3D) absorbers in a highly scattering medium is presented for secure data storage. 3D absorbers are used as data. A highly scattering medium protects data to measure 3D absorbers without knowledge of the scattering coefficient distribution because the phase information is lost during multiple scattering. This prevents an interferometer from measuring the volume medium. To recover the 3D absorbers, a 3D scattering coefficient distribution model is used as prior information and then an iterative method is applied to reduce the difference between the measured and numerical output intensity distributions. A preliminary numerical evaluation is presented.
The speed of modern supercomputers is primarily limited by the relatively slow speed of memory. Research over the past years has focused on developing optical memory systems that, by nature of optics, promise to achieve high speed and high memory capacity. Three- dimensional optical memory systems are well known for their storage capacity and achievable short access time. But the early attempts to exploit 3-dimensional media were limited to photorefractive crystals such as lithium niobate, due to the unavailability of any other suitable medium (alternative media are precluded by their diffraction limited storage densities and non- erasable characteristics). Although volume phase holograms can be recorded in photorefractive crystals, these materials have many obvious flaws such as strong scattering, phase distortion, self diffraction, fast decay, and low refractive index modulation. There have also been continuous efforts to develop new 3-D media (such as photon echo, photorefractive polymers, bacteriorhodusphin, memory access cache, etc., but none can be applied in real world 3-D device because these materials are still in the early stage of development.
We have found that highly efficient waveform recall is possible in coherent transient systems in which the storage is optically thick. Coherent transients may be used in a variety of information storage and processing applications with advantages over traditional electronic methods. However, it is believed that a serious problem in application of photon echoes in practical systems is the relatively low efficiency of the process. We show in our numerical studies that waveform recall efficiencies greater than unity can be achieved in absorbing media with appropriate choice of absorption length and brief pulse area, even for very weak data pulses. We also present our preliminary experimental results in Barium vapor in which efficiencies of 50% were obtained for both the stimulated and two-pulse photon echoes.
Realizing high-fidelity optical information transmission through a scattering medium is of vital importance in both science and applications, such as short-range fiber communication and optical encryption.Theoretically, an input wavefront can be reconstructed by inverting the transmission matrix of the scattering medium.However, this deterministic method for retrieving light field information encoded in the wavefront has not yet been experimentally demonstrated.Herein, we demonstrate light field information transmission through different scattering media with near-unity fidelity.Multi-dimensional optical information can be delivered through either a multimode fiber or a ground glass without relying on any averaging or approximation, where their Pearson correlation coefficients can be up to 99%.
We present the theory and experimental results behind using a 3D holographic signal for secure communications. A hologram of a complex 3D object is recorded to be used as a hard key for data encryption and decryption. The hologram is cut in half to be used at each end of the system. One piece is used for data encryption, while the other is used for data decryption. The first piece of hologram is modulated with the data to be encrypted. The hologram has an extremely complex phase distribution which encodes the data signal incident on the first piece of hologram. In order to extract the data from the modulated holographic carrier, the signal must be passed through the second hologram, removing the complex phase contributions of the first hologram. The signal beam from the first piece of hologram is used to illuminate the second piece of the same hologram, creating a self-reconstructing system. The 3D hologram’s interference pattern is highly specific to the 3D object and conditions during the holographic writing process. With a sufficiently complex 3D object used to generate the holographic hard key, the data will be nearly impossible to recover without using the second piece of the same hologram. This method of producing a self-reconstructing hologram ensures that the pieces in use are from the same original hologram, providing a system hard key, making it an extremely difficult system to counterfeit.
We present the theory and experimental results behind using a 3D holographic signal for secure communications. A hologram of a complex 3D object is recorded to be used as a hard key for data encryption and decryption. The hologram is cut in half to be used at each end of the system. One piece is used for data encryption, while the other is used for data decryption. The first piece of hologram is modulated with the data to be encrypted. The hologram has an extremely complex phase distribution which encodes the data signal incident on the first piece of hologram. In order to extract the data from the modulated holographic carrier, the signal must be passed through the second hologram, removing the complex phase contributions of the first hologram. The signal beam from the first piece of hologram is used to illuminate the second piece of the same hologram, creating a self-reconstructing system. The 3D hologram's interference pattern is highly specific to the 3D object and conditions during the holographic writing process. With a sufficiently complex 3D object used to generate the holographic hard key, the data will be nearly impossible to recover without using the second piece of the same hologram. This method of producing a self-reconstructing hologram ensures that the pieces in use are from the same original hologram, providing a system hard key, making it an extremely difficult system to counterfeit.
We report a novel optical encryption strategy that utilizes highly scattered wavefront of light field to encrypt the plaintext and exploits a scattering medium as the unique physical key. For information decryption, an imaging technique based on the speckle-correlation scattering matrix is adopted to directly extract the wavefront information from speckles, i.e., the ciphertext. The decryption relies on the transmission matrix of the scattering medium which serves as the unique key. In particular, different parts of a scattering medium have absolutely different TMs. Thus, even if attackers get the cryptosystem and repeat the measurement process, they cannot recover the key without knowing the exact part of the medium we used. The security of this scheme is further guaranteed by the advantage that data cannot be leaked without a large percentage (>60%) of the key eavesdropped. In addition, its feasibility and advantage are demonstrated experimentally.