High-Density Er-Implanted GaN Optical Memory Devices.

Upconversion emission has been obtained from Er-focused ion-beam (FIB) implanted GaN. Visible green emission at the 522- and 546-nm range were excited with infrared (IR) laser sources at either 840 or 1000 nm, or with both lasers simultaneously. By implanting closely spaced patterns with the FIB, we demonstrated the concept of storing data in Er-implanted GaN. Information stored as data bits consists of patterns of implanted locations as logic 1 and unimplanted locations as logic 0. The photon upconversion process in Er ions is utilized to read the stored information. This process makes use of the IR lasers to excite visible emission. The integrated upconversion emission power was measured to be ~40 pW when pumped by a 840-nm laser at 265 mW and by a 1000-nm laser at 208 mW. Patterns as small as 0.5 mum were implanted and read. Three-dimensional optical memory based on rare-earth-doped semiconductors could in theory approach a storage capacity of 10(12) bits/cm(3).

Optical digital comparison unit for equal-to, less-than, and greater-than determination.

A number of nonnumerical processing applications, including database management, full text search, and pattern recognition rely heavily on digital comparisons. The development of massive-capacity optical memories coupled with the high speed and parallelism of optics have led to the investigation of optical techniques for nonnumerical processing. This paper proposes a system design for an optical comparator capable of performing multiple equal-to, less-than, and greater-than comparisons between pairs of binary words. The comparator consists of three two-dimensional arrays of optical elements based on a new optical logic device called the light-amplifying optical switch. The first two stages contain inverters, NOR gates, and flip-flops, while the third stage is a custom-designed winner-takes-all network. With a compact design and with small high-speed devices a comparator with 2.5 × 10(4) pixels could theoretically attain a processing rate of approximately 4 × 10(10) 16-bit word comparisons/s.

Optoelectronic data filter for selection and projection.

Database processing, like the majority of nonnumerical applications, exhibits a high degree of functional parallelism but does not require complex operations; therefore it is amenable to optical solutions. The architecture of an optoelectronic filter that is capable of performing selection and projection operations on a two-dimensional data array in a relational database environment is presented. The system receives input from a parallel optical memory, one page at a time, and performs logic operations by using optoelectronic smart pixels based on heterostructure phototransistors and vertical-cavity surfaceemitting lasers. Combinations of AND and XOR gates are used to realize row-lcolumn masking and comparisons of input data against user-supplied search arguments. The main goal of the filter is to reduce the effective data rate between the highly parallel optical storage and the low input data rate conventional electronic computer, thus efficiently interfacing currently available photonic and electronic technologies.

Bitonic sorting using an optoelectronic recirculating architecture.

An optoelectronic bitonic sorter based on a recirculating architecture is presented. The data are input inword parallel-bit parallel fashion and processed by two smart pixel arrays made up of bitwise compare-and-exchange modules. Along with the logic design, the control and synchronization of the bitwise compare-and-exchange modules are discussed. Finally, the capacity, hardware requirements, response time, and throughput of the recirculating bitonic sorter are compared with a pipeline implementation. The proposed recirculating architecture is shown to require less hardware than the pipelined systems. However, the decrease in hardware results in a decrease in system throughput.