Spatial filtering logic based on polarization

Passive all-optical polarization switch, binary logic gates, and digital processor

We introduce the passive all-optical polarization switch, which modulates light with light. That switch is used to construct all the binary logic gates of two or more inputs. We discuss the design concepts and the operation of the AND, OR, NAND, and NOR gates as examples. The rest of the 16 logic gates are similarly designed. Cascading of such gates is straightforward as we show and discuss. Cascading in itself does not require a power source, but feedback at this stage of development does. The design and operation of an SR Latch is presented as one of the popular basic sequential devices used for memory cells. That completes the essential components of an all-optical polarization digital processor. The speed of such devices is well above 10 GHz for bulk implementations and is much higher for chip-size implementations. In addition, the presented devices do have the four essential characteristics previously thought unique to the microelectronic ones.

Binary logic based purely on Fresnel diffraction

Binary logic operations on two-dimensional data arrays are achieved by use of the self-imaging properties of Fresnel diffraction. The fields diffracted by periodic objects can be considered as the superimposition of weighted and shifted replicas of original objects. We show that a particular spatial organization of the input data can result in logical operations being performed on these data in the considered diffraction planes. Among various advantages, this approach is shown to allow the implementation of dual-track, nondissipative logical operators. Image algebra is presented as an experimental illustration of this principle.

Implementation of an optical multiwavelength full adder with a polarization encoding scheme

We propose and demonstrate an optical multiwavelength full adder that uses polarization encoding and fourwave mixing in photorefractive crystals. Optical wavelengths are employed to encode the different bits of binary numbers. By exploiting the spectral parallelism of optics, we can perform multibit operations simultaneously in photorefractive crystals. The polarization encoding scheme permits an easy, accurate implementation of multiwavelength SUM operations. A carry-save full adder also is demonstrated to improve system speed further during multinumber addition and subtraction.

Polarization-encoded optical logic operations in photorefractive media

We propose and demonstrate optical logic operations using polarization encoding and wave mixing in photorefractive crystals. In our approach two orthogonal polarization states of light beams are used to represent respective logic values of 1 and 0. All 16 two-input logic operations can be easily achieved by use of the recording and readout of photoinduced volume gratings in photorefractive crystals. An optical full adder is also proposed and demonstrated.

Optical switching with photorefractive polarization holograms

A switching technique that uses the polarization sensitivity of photorefractive holograms in crystals is experimentally demonstrated. The design is capable of handling a large number of 2 x 2 switching channels with only four holograms. The concept is applicable to either synchronous or asynchronous switching and also to a variety of photorefractive materials.

Polarization-based optical logic using laser-excited gratings

We present a novel way of performing optical logic. The proposed logic device is based on the polarization switching observed in the first-order diffraction from a laser-excited grating in a dye-doped solid.

Programmable optical parallel processor based upon polarization modulation: cascade operations

The architectural considerations and experimental results of a new optical parallel are presented. An array logic concept is introduced as the building blocks of the processor. The processor performs programmable logic operations. Polarization modulation and spatial separation of the modulated light, together with the operation kernel, are keys to programmability for any Boolean logic operation. The operation kernel determines the logic operation to be executed according to instructions simply by spatially filtering encoded light. Real-time programmable cascade logic operations for three patterns are demonstrated experimentally using a liquid crystal spatial light modulator as the operation kernel.

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.

Space-variant operations using an optical parallel processor based on polarization encoding

Space-variant logic operations are carried out using an optical parallel processor that is based on polarization encoding and subsequent spatial separation of the encoded light. In this processor a liquid-crystal spatial light modulator is used as an operational kernel that allows a programmable space-variant operation to be performed on a real-time basis by spatially filtering the encodedlight pixel by pixel.

Optical parallel logic gate using a Pockels readout optical modulator and twisted nematic liquid-crystal cells

We describe an optical polarization parallel logic gate that is based on the two orthogonal polarization states corresponding to the two states of a binary system. The logic gate employs a Pockels readout optical modulator (PROM) and 90 degrees twisted nematic liquid-crystal cells (LCC's). The PROM transforms the binary-coded intensities of the input images into two orthogonally polarized states of readout light. The LCC is employed as a linear polarization rotator that negates the logic state (1 or 0) of the input and output images. Two-dimensional real-time operation of 14 Boolean logic functions for two input images has been demonstrated.

Birefringent encoding and multichannel reflective correlator for optical array logic

A simple image encoding method and a flexible correlator for optical array logic are presented. The encoding method uses the birefringence phenomenon and produces spatial code patterns in parallel for all pixels in two input images. The flexible correlator is composed of a multichannel illuminating system and a segmented reflector, which executes flexible correlation for optical array logic. Using the proposed encoding method together with this correlator, an efficient optical array logic processor capable of executing various parallel neighborhood operations can be constructed.

Programming of optical array logic. 1: Image data processing

Procedures for planning and executing arbitrary parallel processing with optical array logic are generalized as a systematic programming technique of optical parallel processing. Optical array logic is a technique for achieving any parallel neighborhood operation with simple coding and optical correlation. An original symbolic notation facilitates programming of parallel processing with optical array logic, so that many problems can be optically solved using optical array logic. Two examples of image data processing are presented to illustrate the programming procedure of parallel processing with optical array logic.

Optical cellular processor architecture. 1: Principles

General characteristics and advantages of 2-D optical cellular processors are listed and discussed, with reference to the concepts of cellular automata, symbolic substitution, and neural nets. The role of optical interconnections and of quasilinear processing combining linear array operations and pointwise nonlinearities is highlighted. An architecture for optical implementation of cellular automata is introduced; it features high density 3-D optical shift-invariant interconnections and programmability of the interconnection pattern through adequate use of holographic connectors.

Three-dimensional optical interconnection gate array

A recently proposed planar Fredkin gate array for optical interconnections is extended here into a 3-D array that can be implemented using ferroelectric liquid crystal spatial light modulators. Operating as polarization gates these modulators are efficient and can be incorporated into high performance interconnection networks. Some advantages of the new architecture are discussed and performance characteristics are estimated.

Polarization-based optical parallel logic gate utilizing ferroelectric liquid crystals

We describe parallel optical XOR and XNOR logic gates implemented with ferroelectric liquid-crystal (FLC) electro-optic elements to yield naturally a logic in which the binary gate outputs are indicated by two orthogonal polarizations of transmitted light. These gates absorb no power from the incident light beam and hence can be cascaded without the need to regenerate NOT inputs. The FLC elements also confer the advantages of low-voltage, low-power, submicrosecond switching and intrinsic two-state memory. Experimental results demonstrating the XOR and XNOR function are presented, along with measurements of the percentage of polarized light rotated into the two binary states.