Second Wind for Red-Laser DVD Technology?
Idea could disrupt plans for transition to blue-laser optical disks
Tsai, a physicist at the National Taiwan University (NTU) in
Taipei, claims to have proved in principle that his novel adaptation
of red-laser technology will make possible superdense DVDs with
100 GB of information¡Xmore than 20 times the density of the
4.7-GB red-laser disks currently on the market and four times
the density of the first-generation blue-laser disks generally
expected to supplant red-laser technology in a few years.
Lin Wei-chih, a doctoral student of Din-ping Tsai, tunes the
red-laser system that he has designed for superdense DVDs, exploiting
near-field optical effects.
Tsai says the
concept depends on exploiting near-field optical effects occurring at
distances shorter than a wavelength. Near-field effects allow light to
behave as if it had a much shorter wavelength, but they are extremely
sensitive to minute changes in distance from the light source.
Previously, attempts to use the effect focused on ways to keep the
disk drive's laser very close to the disk with very high precision.
coats a regular DVD or CD with two extra layers: a transparent spacing
medium above the recording layer and, on top of that, a "near-field
active" layer in which near-field effects come into play when reading
from or writing to the disk. The spacing layer finesses the problem of
how to keep the light source in constant relation to the targets. The
upshot is that pits as small as 100 nm in diameter can be written and
read, as compared to 400 nm on today's DVDs and 900 nm on CDs.
Tsai's team delivered academic papers describing the system at
conferences last summer, and at the beginning of August NTU received a
five-year NT $166 million grant from Taiwan's Ministry of Economic
Affairs and NT $22.5 million from the National Science Council¡XUS $5.5
million in all¡Xto pursue work on recording technologies using
nano-optics and nanomagnetics. Taiwan's Ritek Corp., the world's
largest maker of optical disks, has supported the team's work and
currently is moving it from laboratory to factory to evaluate its
potential for mass production.
PHOTO: NATIONAL TAIWAN UNIVERSITY