Heads-up! Tech Primer Inside TeraStors NFR

Posted on October 01, 1997


Heads-up! Tech Primer Inside TeraStor`s NFR

Slated for availability early next year, NFR could dramatically after the storage landscape.

Jonathan Hubert

TeraStor Corp

Near-field recording (NFR) is a new technology offering great promise to a storage industry caught in the convergence of the digital information age. As data storage requirements begin to soar beyond the reaches of today`s storage media, new technologies are needed.

NFR is a convergence of technologies. The combination of standard hard-drive and optical-drive technologies allows an NFR drive to read and record data in a unique manner. When the flying optical head inside the drive is positioned less than one laser wavelength from the disk surface, the energy couples from the head to the disk and transfers the data, hence the term "near field."

But that isn`t all that sets NFR apart. A new lens technology allows the optical laser to be focused into a significantly smaller spot size, allowing more data to be written on each track and allowing tracks to be spaced closer together (see sidebar for a technical overview of NFR).

NFR technology is a combination of design elements adapted from several related fields, such as magnetic recording, optical recording, consumer electronics, and microscopy. The key elements of NFR include:

- A flying optical head

- First surface recording

- Crescent recording

In addition to adding its own technologies, TeraStor developed NFR by marrying two patented technologies. One patented technology is the solid immersion lens (SIL), developed in the early 1990s by Dr. Gordon Kino of Stanford. Dr. Kino and his team overcame previous optical limits through a new optical system that provides a radically different approach to reducing the spot size.

The flying optical head, on the other hand, is covered by co-exclusive patent rights granted to TeraStor by Quantum. The basic technology was developed and patented by Digital Equipment, but passed along to Quantum when the company acquired Digital`s storage business.

It is expected that NFR will enable a significant increase in areal density, compared with current storage technologies, and will find its way into storage- intensive business and end-user applications such as publishing, entertainment, education, communications, and the Internet. Design plans call for further increases in areal densities of more than 100 times the current level of 20 GB per disk surface within 10 years, yielding huge capacities in storage devices: terabyte removable disk cartridges and multi- terabyte hard drives.

With the planned enhancements, NFR could maintain an order of magnitude areal density advantage over projected advancements for conventional disk drives (see diagram).

The capacities of mass storage devices needed to store digital content range from several megabytes in hand-held computers or digital cameras to many gigabytes in today`s PC systems to terabytes and petabytes in massive on-line databases or near online and off-line libraries used to back up these databases. To achieve such capacities today, many different technologies must be used, each having its own performance and cost attributes.

NFR has the potential to affect each of the major storage categories: disk, tape, and optical. In speed, capacity, cost, and increased functionality, NFR combines some of the best features of each product category.

According to Jim McCoy, CEO of TeraStor and founder of Quantum and Maxtor, NFR drive pricing will be on par with current storage solutions, but at a significantly lower cost per gigabyte. [Editor`s note: Final pricing and specs such as data transfer rate have not been announced.] McCoy cites technology agreements between TeraStor and such manufacturers as Seagate, Imation, Texas Instruments, and Olympus as well as licensing agreements with other major storage suppliers as additional reasons why the technology will flourish.

NFR-based products will provide the affordable, high-capacity storage solutions needed to manage the large volumes of digital information being created today. In terms of removable media applications, NFR will be an ideal solution for backup and archive and will provide data interchangeability. Compared to tape, NFR will offer faster random access. For fixed hard-drive applications, NFR will provide the capacities and access times needed for large on-line solutions.

Products based on NFR technology are expected to be used in large data centers, high-powered workstations, networks, vertical applications, and individual desktops. Small businesses and home computer users will also realize the benefits of this multipurpose storage solution for a new generation of multimedia products and applications.

The ultimate promise of NFR technology is to reduce the fundamental limiting factors of the coming digital convergence by increasing affordable capacity and enabling new ways of managing and sharing digital content.

Click here to enlarge image

Click here to enlarge image

How NFR works

Near-field recording (NFR) includes technologies adapted from several related fields, including magnetic recording (hard-disk drives), optical recording (lasers), consumer electronics, and microscopy. When the various components are combined, the result is a technology initially capable of storing 20 GB on one side of a 5.25-inch disk.

Some of the key elements that make NFR possible are a flying optical head, a solid immersion lens (SIL), first- surface recording, and crescent recording. Each element contributes to the capacity, performance, and cost advantages provided by NFR.

The flying optical head (similar to flying heads used in hard-disk drives) offers the simplicity and low cost normally associated with hard- disk drives. It allows the recording element to be placed close enough to the recording media so that the distance between them is less than the wavelength of the laser light, hence the term "near field." One of the key optical components inside the flying head is the solid immersion lens, which is used to tightly focus a laser beam to produce an ultra-small spot. The energy from this spot is then transferred--or coupled--onto the first surface (top surface) of a disk in an effect known as evanescent coupling.

Evanescent coupling, or the transfer of laser energy, heats a spot on the recording surface to a temperature of about 300 Celsius in roughly one nanosecond. At this temperature, called the Curie point, the irradiation heats the molecules in that spot to a finite depth, enabling magnetization when placed within a magnetic field. This magnetic field (positive or negative) is pulsed into the heated spot by the magnetic coil embedded within the read/write head (see above diagram).

This implementation has two important advantages:

Direct overwrite. Through high-speed switching of magnetic pulses, the small head-based coil is able to directly overwrite without requiring a complete rotation of the disk, as is necessary with most magneto-optical (MO) technologies.

Two-sided recording. By embedding the magnetic coil in the head rather than behind the disk, as with traditional MO devices, NFR supports two-sided disks with two heads on-line per disk.

The tiny magnetic coil in the flying head switches fast enough to write the ultrasmall "bit domains" in overlapping sequences, creating a series of crescent-shaped bits of information on the disk. This process is called crescent recording (see diagram below).

Crescent recording effectively doubles the bit density, providing even higher areal densities and allowing NFR technology to achieve storage densities that are an order of magnitude higher than current conventional technologies. Furthermore, this advantage is sustainable to capacities of hundreds of gigabytes per disk as the lens shape, lens materials, read channels, and eventually, the wavelength of the laser itself-as well as other elements of the system-improve over time. Just as important, NFR technology draws heavily on MO and hard-disk-drive materials and processes, enabling low manufacturing costs and production ramps-comparable to those of current high-volume hard-disk-drive technology.

Click here to enlarge image

Click here to enlarge image

Jonathan Hubert is director of product marketing at TeraStor Corp. in San Jose, CA.

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