History (1990): Optical Memory With Amazing Specs from Optex

Optex Corporation (Rockville, MO) is developing a new computer memory system apparently unrivaled by existing products.

It utilizes Electron Trapping Optical Memory (ETOM) disk based on the principle of photonics. The firm is taking technology beyond all current memory systems, including Winchester and magneto-optical drives. The media is nearly indestructible, with storage capacity and speed exceeding those of every system in use. In test, ETOM can perform virtually unlimited write/erase operations without altering the material. The media has attained hundred million R/W erasable cycles without degradation or change in the physical characteristics of the media.

“Magneto-optical media has demonstrated one million such cycles, while phase change and dye polymer devices have only successfully completed thousands of cycles,” said Dr. Joseph Lindmayer, founder and president of Optex.

The Hungarian physicist, now 60 years old, came to the U.S. in 1956 where he organized solid state activity at Comsat laboratories. Five years later, he formed Solarex and Semix, photovoltaics firms. The firs one counted about $25 million 10 years later. The two companies were sold to the oil giant Amoco Corp. (former Standard Oil of Indiana) in 1983. Afterwards, he formed a new company, Quantex Corp., to explore the principle of photonics, and then Optex to develop them. He has commercialized several new technologies, published extensively and holds over 70 patents. (He died in 1995. Editor)

Because the low-power lasers used to write and read an ETOM disk are not required to provide spot heating, it offers significant advantages over other erasable optical memory technologies, which all depend on local heating to write and erase.

A high-powered 35mW laser diode is required for M-O media. ETOM media employs light from lasers with a few percent of such power. ETOM system uses specifically developed infrared-sensitive materials which store information by the phenomenon of electron trapping. Electrons are raised to an elevated energy state by visible light and stored there in trapping sites. When stimulated by infrared light, the electrons return to the ground of state, releasing optical energy. This effect can be used to write, read and erase data trough a purely photo-electronic process, without altering the material itself. Digital information is conveyed by the presence or absence of electrons in traps at a given location. The data rate capability is expected to reach well into the tens of megabytes per second.

“It is much faster than the 2.8Mb/s maximum transfer rate (at 3,600rpm) that has been announced for magneto-optical drives,” said Lindmayer.

Rotating the disk at 1,8Mb/s. Optex anticipates a next level of 15Mb/s at a signal frequency of 10MHz and a rotation rate of 5,400rpm, with further increases expected.

“The speed of an M-O system is limited by the need to heat the media to change its magnetic properties,” added Lindmayer. “The inherent speed, however, of the ETOM media (less than 5 nanosecondes) means that the overall system speed is limited only by the speed of other components.”

The new media is a crystalline layer of certain II-VI solid state compound doped with various impurities which can store information in the form of trapped electrons. ETOM can utilize both sides of a 5,25-inch disk with a 550MB capacity per side. Layering the patented electron-trapping materials could triple that density, and even reach 4GB or more. Further developments are also planned.

The ETOM system can be extended into the third dimension by depositing multi-Iayers. Electron trapping memory disks can be turned into permanent memories, even sectionnally. Permanent copies of a whole disk are also possible by contact printing to a photosensitive blank disk.

Anthony Clifford, director of corporate development, expects to have a commercially available product by the end of 1991, at a price compatible with M-O drives.

Last February, Optex announced the completion of a conceptual design of an optical disk drive for its removable media developed by Vision Three, Inc. (New York, NY), a firm directed by Leonard Laub.

“They chose a concept which incorporated as much commercially available hardware as possible,” said Lindmayer. “This has two advantages to us, first to prove the compatibility of our media with existing components, and second, it will allow us to get a product to market in the shortest time possible.“

A current drawback to M-O disks is their inability to have direct overwriting capabilities. But the next phase-change disks won’t have this problem anymore.

The electron trapping method has nevertheless a few disadvantages. It needs a different architecture to exchange data with computers. And it requires a refresh every time the disk is read: each time you read an information, you have to put it back. We’ll still have to wait until Optex can persuade at least one big computer industry or a large hard disk manufacturer (Maxtor?), the only way for it to convince the market.

Founded in 1986, now with 70 employees, Optex Corporation (Richmond, MD) is a privately-held company involved in the R&D of ETOM system based on a class of phosphor materials developed at Quantex Corporation (its sister company), a suburban Washington D.C. laboratory started in 1984. Optex was formed as a spin-off from Quantex 4 years ago to focus on computer disks based on ETOM technology avoiding the use of traditional magnetic media. One of the more significant investments ($2 million) came from Gryphon Ventures, a Boston-based venture capital firm. The US Department of Defense awarded Optex $1.5 million in research contracts, with an additional $2 million expected. Quantex was notably founded through an R&D contract with Siemens AG (West Germany) for a high-contrast low dosage X-ray film system. As from 1988, Quantex became a profitable company with $5 million in sales, coming from various products and defense contracts.