(July 1, 2015) DVDs
and Blu-ray disks contain so-called phase-change materials that morph from one
atomic state to another after being struck with pulses of laser light, with
data "recorded" in those two atomic states. Using ultrafast laser
pulses that speed up the data recording process, Caltech researchers adopted a
novel technique, ultrafast electron crystallography (UEC), to visualize
directly in four dimensions the changing atomic configurations of the materials
undergoing the phase changes. In doing so, they discovered a previously unknown
intermediate atomic state—one that may represent an unavoidable limit to data
recording speeds.
By shedding light on the fundamental physical processes
involved in data storage, the work may lead to better, faster computer memory
systems with larger storage capacity. The research, done in the laboratory of
Ahmed Zewail, Linus Pauling Professor of Chemistry and professor of physics,
will be published in the July 28 print issue of the journal ACS Nano.
When the laser light interacts with a phase-change material,
its atomic structure changes from an ordered crystalline arrangement to a more
disordered, or amorphous, configuration. These two states represent 0s and 1s
of digital data.