Pierre Cambon

Bistability and nonlinearity in optically addressed ferroelectric liquid-crystal spatial light modulators: applications to neurocomputing.

We report the characteristics of a truly bistable optically addressed ferroelectric liquid-crystal spatial light modulator that is capable of storing binary images. We show that, in addition to this bistability, a nonlinear response and gray scales can be observed under certain operating conditions. We then report on how these capabilities can be used in implementing optical neurocomputing architectures.

Mathematical morphology processor using ferroelectric liquid crystal light valves: principle

We describe the principle of an optical digital processor for mathematical morphology (MM). The proposed central processing unit is based on binary logic using states of polarization and spatial data shift using geometric optics. Two dimensional Boolean operations are performed by means of logical gates using ferroelectric liquid crystal light valves, which are shown to be able to perform iterative processes well suited to MM operation implementation. A complete optical architecture is proposed from which the programming of elementary MM transformations is demonstrated.

Controlling the grey level capacity of a bistable FLC spatial light modulator

Abstract Due to their memory, non-linear response and threshold, as well as their grey level capacity, ferroelectric liquid crystal spatial light modulators are useful devices for optical implementations of neural networks. We propose a phenomenological explanation of the roles, the different driving parameters like the voltage, the current and the length of the addressing pulse play in achieving and controlling these grey levels. Finally we discuss a possible optical implementation of a self organizing memory based on the model of the Kohonen map, using optically addressed SLMs.

Morphological filtering using a Fourier transform hologram

Abstract We illustrate how morphological operators can be expressed in terms of Fourier optics using the properties of the Fourier transform hologram. Experimental results are presented exhibiting basic operations which are usually involved in morphological filtering. These results are compared with those obtained from a digital computer.

Experimental results of the implementation of an optical compressing and multiplexing method

The growing sizes of the images as well as their complexities have reduced the competitiveness of the digital compression and multiplexing. These new requirements led the scientific community to look for new methods which will be adapted to these new demands. In this article, according to this objective, we propose and validate an all optical architecture implementing a new method of optical compression and mutliplexing. This method is based on a new technique of segmentation of Fourier plane (distribution of spectra in various zones according to a well defined criterion). This segmentation is aiming at neutralizing the redundant information appropriate for each sepctrum and multiplexing these verious spectra in the Fourier plane.

Multidecision optical correlator using a new approach for the segmented phase-only filter (SPOF)

In this article, we propose to return to the simplest optical architecture and to transfer all the recognition intelligence in to the filter design. However the use of such a filter to carry out multiple correlations in parallel poses the problem of product space bandwidth limitation in the filter plane (Fourier plane): information on references is injected into the filter by a frequentially multiplexing of the references constituting the training base. From this point of view, we propose an optimization of the segmented filter in order to increase its performance and its capabilities.

Parallel access read/write binary spatial registers for digital optical computing architectures

We describe a new type of bistable, optically addressed ferroelectric liquid-crystal spatial light modulator to be used as a binary spatial register. The good contrast ratio of the devices suggests their use in cascaded architectures or in optical feedback loops. We investigate these cascading abilities with a view to digital optical computing applications.

Foundry-fabricated hybrid GaAs VCSEL-based smart pixel

In this paper, we propose a foundry fabricated hybrid VCSEL- based GaAs smart pixel devoted to high speed and low cost optical interconnections. The device has an optical gain of 10.4 dB for power consumption less than 1 W. Moreover, the -3 dB bandwidth is suitable for transmission rate up to 6 Gbit/s.

16×16 self-routing cell switch using polarization-controlled vertical cavity surface emitting laser arrays: principles

The principle and design of a self-routing 16316 free-space optically interconnected crossbar cell switch are detailed. Vertical cavity surface emitting lasers (VCSELs) and VCSEL-based smart pixel arrays are key devices for this system and enable high density interconnection. Using the optical switching of VCSEL polarization extensively, the cell switch exhibits a potential high bit rate and low reconfiguration time be- tween two cells. Moreover, because of the high speed switching of the VCSEL between its two linear polarizations, address substitution, which is one of the asynchronous transfer mode (ATM) requirements, can be implemented. A compact cell-switch demonstrator is proposed that uses low-cost optically recorded holograms and microlens arrays.

Optically addressed spatial light modulator with nipin aSi:H layers and bistable ferroelectric liquid crystal

The aimed requirements for optical processing device described here are the short term memory, high resolution and high frame rate, cascadability, high fan-out. One of the simpler candidate devices for such requirements are the bistable optically addressed liquid crystal spatial light modulators.