Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Journal of the Optical Society of America B

All-optical associative memory based on a nonresonant cavity with image-bearing beams

M. Ingold, M. Schadt, M. Duelli, Peter Günter

Published Aug 1, 1992• 8 citations
Publisher

Abstract

A new implementation of an all-optical associative memory is presented. It is realized in a nonresonant cavity containing a photorefractive and a nematic liquid crystal. The images, which are stored on slides, modulate the intensities of the signal beams circulating in the cavity. In a photorefractive KNbO3 crystal the signal images are compared with an arbitrary input image on the pump beam by multiple two-beam coupling. In the nematic liquid-crystal cell the signal images are thresholded by a feedback-induced optical bistability. Associative readout, error correction, and image completion are demonstrated for two and three stored black-and-white images. The performance of the new scheme is estimated to be comparable with that of nonlinear holographic associative memories based on thin holograms.

DOI
10.1364/josab.9.001327

Related papers

All-optical associative memory using photorefractive crystals and a saturable absorber

Markus Duelli, Roger Sean Cudney, Claudia Keller +1 more

We report on the investigation of a new configuration of an all-optical associative memory. The images to be recalled associatively are stored in a LiNbO3 crystal via angular multiplexing. Thresholding of the reconstructed reference beams during associative readout is achieved by using a saturable absorber with an intensity-tunable threshold. We demonstrate associative readout and error correction for 10 strongly overlapping black-and-white images. Associative recall and full reconstruction is performed when only 1/500 of the image stored is entered.

Optical Engineering•Jul 1, 1995•8 citations

Optical bistability and beam competition in a nonresonant cavity containing a nematic liquid crystal and a photorefractive crystal

M. Ingold, M. Schadt, Peter Günter

Several configurations for the optical bistability of a nematic liquid crystal in a nonresonant cavity are investigated. These bistabilities result from optical feedback and occur below the Freedericksz transition. An electric-field-induced optical switching with hysteresis is observed as well. Photorefractive two-wave mixing in a KNbO3 crystal is used for amplification of the feedback beam, leading to an optical hysteresis with the pump beam of the photorefractive amplifier as the control beam. In this configuration competition between two beams injected into the nonresonant cavity (optical thresholding) is demonstrated: The stronger beam is identified and discriminated from the weaker one by bistable switching.

Journal of the Optical Society of America B•Dec 1, 1990•5 citations

Self induced coherent light resonators with photorefractive KNbO3crystals

Gilles Pauliat, M. Ingold, Germano Montemezzani +1 more

Associative optical memories have attracted increasing interest as they can offer new, all-optical solutions to various problems, for example in pattern recognition. In such memories, stored informations are retrieved from partial or noisy inputs. An optical laser resonator can act as such an associative processor. Using holograms, different images are associated to each of the modes of the optical cavity. Thus a partial input image can force the resonator to oscillate on the closest stored information. Two wave mixing arrangements in photorefractive crystals, which provide very large amplification factors, can be used to overcome the large losses inherent to these resonators.

Ferroelectrics•Apr 1, 1989•0 citations

Holographic associative memory using a coherently induced double phase conjugate mirror

Xiudong Sun, Zhongxiang Zhou, Yan Li +3 more

We demonstrate a new method to implement holographic associative memory based on a coherently induced double phase conjugate mirror that has phase-conjugate reflectivity larger than unity for weak reference signal over a large range of pumping-reference intensity ratio. The phase conjugator, operated with a copper-doped KNSBN crystal, serves as a novel nonlinear feedback and gain element for the associative memory system. A vanadium-doped KNSBN crystal as storage medium improves the response speed of the holographic recording process. A stored image has been completely retrieved when a partial input addresses the associative memory system.

Optical Engineering•Aug 1, 1996•3 citations

Optical bistability of a nematic liquid crystal with photorefractively amplified feedback

M. Ingold, J. Keller, Gilles Pauliat +1 more

Optical bistability has been observed in a new configuration consisting of a nematic liquid crystal (ROTN 403) and a photorefractive crystal (KNbO3). The nematic liquid crystal (NLC), placed between crossed polarizers, serves as an optically controlled gate. The transmitted signal beam is amplified by photorefractive two-wave mixing and sent back onto the NLC in such a way that it changes the transmission of the gate. Bistability of the optical signal in the feedback loop with a large hysteresis is found. The bistable hysteresis curve depends on the nonlinearities of the NLC and of the photorefractive crystal, on the intensity of the storage beam and on the losses in the feedback loop.

Ferroelectrics•Apr 1, 1989•5 citations

Optical Bistability of a Nematic Liquid Crystal with Photorefractively Amplified Feedback

M. Ingold, K. Totland, Gilles Pauliat +2 more

Light induced changes of the refractive index in a nematic liquid crystal [1] and in a photorefractive crystal (KNbO3) [2] have been used to design an optically bistable device [3]. In the nematic liquid crystal (NLC) light can reorient biréfringent molecules. Therefore the NLC, placed between crossed polarizers, acts as an optically controlled gate. In the KNbO3 crystal photorefractive two-beam coupling is used for light amplification.

Photorefractive Effects, Materials, and Devices•Jan 1, 1990•0 citations
A new implementation of an all-optical associative memory is presented. It is realized in a nonresonant cavity containing a photorefractive and a nematic liquid crystal. The images, which are stored on slides, modulate the intensities of the signal beams circulating in the cavity. In a photorefractive KNbO3 crystal the signal images are compared with an arbitrary input image on the pump beam by multiple two-beam coupling. In the nematic liquid-crystal cell the signal images are thresholded by a feedback-induced optical bistability. Associative readout, error correction, and image completion are demonstrated for two and three stored black-and-white images. The performance of the new scheme is estimated to be comparable with that of nonlinear holographic associative memories based on thin holograms.
We report on the investigation of a new configuration of an all-optical associative memory. The images to be recalled associatively are stored in a LiNbO3 crystal via angular multiplexing. Thresholding of the reconstructed reference beams during associative readout is achieved by using a saturable absorber with an intensity-tunable threshold. We demonstrate associative readout and error correction for 10 strongly overlapping black-and-white images. Associative recall and full reconstruction is performed when only 1/500 of the image stored is entered.
Several configurations for the optical bistability of a nematic liquid crystal in a nonresonant cavity are investigated. These bistabilities result from optical feedback and occur below the Freedericksz transition. An electric-field-induced optical switching with hysteresis is observed as well. Photorefractive two-wave mixing in a KNbO3 crystal is used for amplification of the feedback beam, leading to an optical hysteresis with the pump beam of the photorefractive amplifier as the control beam. In this configuration competition between two beams injected into the nonresonant cavity (optical thresholding) is demonstrated: The stronger beam is identified and discriminated from the weaker one by bistable switching.
Associative optical memories have attracted increasing interest as they can offer new, all-optical solutions to various problems, for example in pattern recognition. In such memories, stored informations are retrieved from partial or noisy inputs. An optical laser resonator can act as such an associative processor. Using holograms, different images are associated to each of the modes of the optical cavity. Thus a partial input image can force the resonator to oscillate on the closest stored information. Two wave mixing arrangements in photorefractive crystals, which provide very large amplification factors, can be used to overcome the large losses inherent to these resonators.
We demonstrate a new method to implement holographic associative memory based on a coherently induced double phase conjugate mirror that has phase-conjugate reflectivity larger than unity for weak reference signal over a large range of pumping-reference intensity ratio. The phase conjugator, operated with a copper-doped KNSBN crystal, serves as a novel nonlinear feedback and gain element for the associative memory system. A vanadium-doped KNSBN crystal as storage medium improves the response speed of the holographic recording process. A stored image has been completely retrieved when a partial input addresses the associative memory system.
Optical bistability has been observed in a new configuration consisting of a nematic liquid crystal (ROTN 403) and a photorefractive crystal (KNbO3). The nematic liquid crystal (NLC), placed between crossed polarizers, serves as an optically controlled gate. The transmitted signal beam is amplified by photorefractive two-wave mixing and sent back onto the NLC in such a way that it changes the transmission of the gate. Bistability of the optical signal in the feedback loop with a large hysteresis is found. The bistable hysteresis curve depends on the nonlinearities of the NLC and of the photorefractive crystal, on the intensity of the storage beam and on the losses in the feedback loop.