Incremental recording for photorefractive hologram multiplexing

Taketomi, Yoshinao; Ford, Joseph E.; Sasaki, Hirokazu; Ma, Jiang; Fainman, Yeshaiahu; Lee, Sing H.

doi:10.1364/ol.16.001774

Cited by 132 publications

(34 citation statements)

References 7 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In the optical field there has been constant efforts on both multiplexed [1] and security encrypted [2] data stor age. Securing data in high-capacity storage systems is one of the challenging tasks in order to meet user-requirements in data storage.…”

Section: Introductionmentioning

confidence: 99%

Multiplexing encrypted data by using polarized light

Barrera

Henao

Tebaldi

et al. 2006

Optics Communications

107

View full text Add to dashboard Cite

We investigate the feasibility of multiplexing, employing polarized light, a set o f security encrypted data. The encryption approach is based on the double random pure-phase enciphering method. Phase conjugation operation is conducted in the reconstruction stage with the aid o f a photorefractive crystal which stores the encrypted information. When storing each encrypted image, a polarization change is introduced in the system. This induces decorrelation on the speckle patterns inside the storing medium. We apply this approach for multiple image encryption. We show experimental results that confirm our approach. © 2005 Elsevier B.V . A11 rights reserved. IntroductionIn the optical field there has been constant efforts on both multiplexed [1] and security encrypted [2] data stor age. Securing data in high-capacity storage systems is one of the challenging tasks in order to meet user-requirements in data storage.Optical data storage presents great advantages over tra ditional non-optical storage systems with the potentiality of low cost, high storage capacity, high transfer rate, and hardware-based data encryption. To overcome the difficul ties concerning the storage means for recording photorefractive crystals have been used.There are many methods for multiplexing holograms, e.g., wavelength-, shift-, angle-, and phase-coded multiplexing. Several efforts were performed thanks to the advent of the liquid crystal spatial light modulator (LC SLM). It has opened up the possibility for dynamic control of ampli tude, phase or polarization state of light. The use of LC SLMs for the spatial control of the state of polarization has already been described and experimentally demon strated [3].Several optical systems based on the encryption of information using phase components of wave front have been experimentally demonstrated [4 6], Polarization has been used for the visualization of the decoded information. Two dimensional encoding of the polarization state of light using a parallel aligned liquid crystal SLM has recently been demonstrated [7]. Unnikrishnan et al. [8] experimentally demonstrated an optical encryption system based on polarization encoding to encrypt binary images. The encryption is done by XOR operation between the image and a random code (key to the encrypted image). The XOR operation is done in the polarization domain of coherent light by using two ferroelectric liquid crystal spatial light modulators. The

show abstract

Section: Introductionmentioning

confidence: 99%

Multiplexing encrypted data by using polarized light

Barrera

Henao

Tebaldi

et al. 2006

Optics Communications

107

View full text Add to dashboard Cite

show abstract

“…6 Multiplexing holograms obtained by use of incremental recording have also been investigated for monoexponential recording and erasure dynamics. 7 In doubly doped crystals, however, the erasure curves are not monoexponential, and therefore a modified recording schedule must be employed. In this Letter we propose and experimentally demonstrate such a recording schedule for multiplexing many persistent holograms in doubly doped LiNbO 3 with equal diffraction efficiencies.…”

mentioning

confidence: 99%

Multiplexing holograms in LiNbO_3:Fe:Mn crystals

Adibi

Buse

1999

Opt. Lett.

View full text Add to dashboard Cite

Persistent holograms are recorded with red light in lithium niobate crystals doped with manganese and iron. Different erasure mechanisms are investigated, and a recording schedule for multiplexing holograms with equal diffraction efficiencies is proposed. To test the recording schedule experimentally, we multiplex 50 plane-wave holograms with the proposed recording schedule. © 1999 Optical Society of America OCIS codes: 090.0090, 210.2860, 090.2910 We recently demonstrated persistent (nondestructive readout) holographic recording in doubly doped lithium niobate ͑LiNbO 3 ͒.1 Two-center holographic recording is one type of gated holographic recording. -5In multiplexing many holograms, we need a recording schedule to equalize the diffraction efficiencies of all holograms. There is a well-known recording schedule for the case in which recording and erasure of a single hologram can be represented by monoexponential formulas. Multiplexing holograms obtained by use of incremental recording have also been investigated for monoexponential recording and erasure dynamics. 7In doubly doped crystals, however, the erasure curves are not monoexponential, and therefore a modified recording schedule must be employed. In this Letter we propose and experimentally demonstrate such a recording schedule for multiplexing many persistent holograms in doubly doped LiNbO 3 with equal diffraction efficiencies.We performed experiments with a congruently melting x-cut LiNbO 3 crystal doped with Fe and Mn. The crystal is oxidized so that initially all Fe traps are empty and a portion of the Mn traps are filled. Illumination with UV light (for example, at 404 nm) excites electrons from Mn centers to the conduction band. A portion of these electrons is trapped by Fe centers. Therefore, the crystal becomes sensitive to red light. Holographic recording is achieved by the simultaneous presence of UV and two red beams interfering in the crystal. The red beams create a charge distribution at the Fe and the Mn trapping sites that is proportional to the interference pattern, and the UV light provides continuous sensitization of the Fe traps. Readout is performed with one red beam only, with no UV light present. During readout, all electrons in the Fe centers will be transferred to the Mn centers. This partially erases the hologram. After all electrons are transferred to the Mn centers, further red readout of the remaining hologram in the Mn traps is nondestructive. A typical recording and readout curve is shown in Fig. 1.When multiple holograms are recorded, each hologram is erased by both UV and red beams during the recording of subsequent holograms. We performed a series of recording and erasure experiments to assess the dynamics of the processes and to measure the time constants involved. We performed erasure with the UV light and one of the red beams to get information about the erasure of a hologram while subsequent holograms were recorded. Experimental results for four cycles of recording and erasure are depicted in Fig. 2. The recording curve...

show abstract

“…Previously suggested schemes for scheduled 3 ' 6 and incremental 5 multiplexing conclude that the diffraction efficiency of one hologram, when N volume holograms are stored, decreases with 1/N 2 . This is because when one hologram is recorded, all previously stored ones are not Bragg matched to the interfering beams and hence experience erasure.…”

mentioning

confidence: 99%

Reduction in the reconstruction error of computer-generated holograms by photorefractive volume holography

et al. 1993

View full text Add to dashboard Cite

We suggest a method for coding high-resolution computer-generated volume holograms.It involves splitting the computer-generated hologram into multiple holograms, their individual recording as volume holograms by use of the maximal resolution available from the spatial light modulator, and subsequent simultaneous reconstruction.We demonstrate the recording and the reconstruction of a computer-generated volume hologram with a space-bandwidth product much higher than the limitation imposed by the interfacing spatial lightmodulator. Finally, we analyze the scheduling procedure of the multiple holographic recording process in photorefractive medium in this specific application.Binary computer-generated holograms (CGH's) are becoming essential components in optical signalprocessing schemes. Apart from their use as a means for storage and reconstruction of images, these holograms can serve as spatial filters, optical elements, and the basic component in interconnection networks. CGH's are created in an electronic computer and are displayed on spatial light modulators (SLM's). This provides real-time variability, which enhances the flexibility of the holograms and makes them suitable for applications such as adaptive optics and reconfigurable interconnects. Unfortunately, most currently available SLM's suffer from a limited information capacity, which substantially deteriorates the space-bandwidth product of the CGH's and results in a undesired difference between the original image and the one actually reconstructed from a CGH.

show abstract

Incremental recording for photorefractive hologram multiplexing

Cited by 132 publications

References 7 publications

Multiplexing encrypted data by using polarized light

Multiplexing encrypted data by using polarized light

Multiplexing holograms in LiNbO_3:Fe:Mn crystals

Reduction in the reconstruction error of computer-generated holograms by photorefractive volume holography

Contact Info

Product

Resources

About