Smart Optical Memory

Sequential computers are fast approaching the fundamental physical limits of performance. Computers capable of parallel processing are being used to improve performance. These parallel computers or processors require fast, dense, affordable, intelligent main and cache memories. SRI International is developing a high density, random access, smart time-domain optical memory TDOM to meet the above needs. SRI performed experiments to examine the practicality of the photon echo approach to serial data storage. SRI successfully demonstrated a storage density of 2 Kbits in frequency channels 110 MHz wide in Eu doped Y2SiO5 crystal at an inputoutput speed of 40 MHz. No measurable cross-talk between adjacent frequency channels was observed. From these measurements, a memory density of 6.25 x 10exp 4 bitsfocal spot was inferred, which is the highest storage density demonstrated to date. This work shows that this serial architecture for optical data storage is extremely valuable for applications such as all-optical switching. SRI International also performed a feasibility study to examine the use of stimulated echo technique for parallel optical data storage. In a proof-of-principle experiment, a total of 100 single-page holograms were stored and later recalled successfully. The results suggest a frame transfer rate exceeding 10exp 3 frames per second along with a high storage density. The experimental results from this project clearly demonstrate the feasibility of the TDOM for high speed, high density, optical data storage application using existing technology.