Michael Edward Prise

Dammann Gratings For Laser Beam Shaping

Dammann gratings are binary phase gratings that are used to produce a one- or two-dimensional array of equal-intensity light spots. Recently, Dammann gratings have become of interest for their ability to provide the optical power supply to an array of optical logic devices from a single laser source. We present here a feasibility study of Dammann gratings, in which we consider several parameters that are important for the computation and fabrication of the gratings. As a result of this investigation we conclude that Dammann gratings are useful for array sizes up to about 40 x 40 spots. Above that size, problems with the computation of the gratings and with the resolution become dominant.

Module for optical logic circuits using symmetric self-electrooptic effect devices

An optical module designed to perform cascadable optical logic using arrays of symmetric self-electrooptic effect devices (S-SEEDs) is described. The operation of an array of 7 x 3 devices with optical windows spaced by 20 microm is demonstrated including both array preset and individual device switching. The issues leading to the design of this optical system are detailed. This work illustrates some of the issues which must be considered when designing systems using small reflecting electrooptic devices such as SEEDs and free-space optics in digital systems.

Free-space optical interconnection scheme.

As integrated circuit linewidths are reduced, single chip system functionality and speed increase. Conventional electronic chip input/output does not scale with this trend: bonding pad sizes and off-chip capacitive loads remain essentially constant. The shortage of chip interconnect capability has become critical. Integrated free-space optical interconnect has the potential to overcome this problem by providing a large number of high speed connections between chips. This paper describes methods for performing free-space intermodule optical interconnections within a digital electronic computer utilizing large arrays of light beams. A particular architecture and its ongoing implementation with integrated components are discussed.

Optical considerations in the design of digital optical computers

The promise of digital optical computing is based on massively parallel interconnections between logic gates, which allow for novel architectures, and the possibility of ultrafast switching devices. This paper spells out the computational requirements and limitations for non-linear optical devices and optical interconnects. Relationships between the optical properties of devices (transmission and contrast) and their potential computational properties (fanin and fanout) are derived. The accuracy of the intensity levels required in the system are estimated. The requirements for a minimal device useful for digital optical computing are stated. The ‘volume’ of a device in phase-space limits fanin, switching energy and the degree of space variance in the interconnections. Space-invariant and space-variant interconnections are compared. Limits of random interconnects by volume holograms are discussed.

An integrated free space optical bus

As integrated circuit linewidths are reduced, single-chip system functionality and speed increase. Conventional electronic chip input/output does not follow this trend: bonding pad sizes and off chip capacitive loads remain essentially constant. Shortage of chip interconnect capability has become critical. Integrated free-space optical interconnect has the potential to overcome this problem by providing a large number of high-speed connections between chips. A description is given of the application of free-space optics, quantum-well modulators, and CMOS photodetectors to this task.<<ETX>>

Optical digital processor using arrays of symmetric self-electrooptic effect devices

Four arrays of thirty-two GaAs symmetric self-electrooptic effect devices were optically interconnected to form a looped-pipeline optical digital processor. Several circuits were demonstrated, including two shift registers and a decoder circuit. Clock frequencies of up to 1 MHz were attained. Possible extensions to and limitations of this system are described.

Optical circuitry for free-space interconnections

A means for losslessly implementing arbitrarily space-variant optical interconnections in free space without sacrificing optical space-bandwidth product or power is described. The technique uses space-variant mirrors and polarization beam splitters to separate and combine sets of device output spots, where a different interconnection operation is performed on each spatially separable set. These space-variant mirrors are inexpensive and easily fabricated. Example applications for Banyan interconnections and laser array combination are presented. Current experimental limits are discussed.

Cascaded operation of arrays of symmetric self-electro-optic effect devices.

Two identical optical modules were used to demonstrate the cascaded operation of 32-element arrays of symmetric self-electro-optic effect devices. The devices had 5 microm x 10 microm optical windows spaced on a square grid with a 20-microm spacing. They were operated as optically interconnected inverters at 1.1 MHz. The optical power was provided by two current modulated laser diodes per array, each with a maximum output power of 9 mW. The operation of the devices as logic gates is optically implemented but not demonstrated.

Optical computing using self-electro-optic effect devices

The use of GaAs SEEDs (Symmetric self-electro-optic effect devices) and free space optics as interconnect in digital processing systems is discussed. Systems based on using the optical interconnect at the inter-gate and the inter-chip level are described.

Computational Properties of Nonlinear Optical Devices

We derive the relationships between the optical properties of devices (transmission and contrast) and their potential computational properties(fan-in and fan-out),when used in an optical digital computer. The required accuracies of the optical system are discussed.