All-optical data memory: ultra-short light pulses make the
GST material change from crystalline to amorphous and back. Weak light pulses
read out the data.
Credit: C. Rios/Oxford University
The first all-optical permanent on-chip memory has been
developed by scientists of Karlsruhe Institute of Technology (KIT) and the
universities of Münster, Oxford, and Exeter. This is an important step on the
way towards optical computers. Phase change materials that change their optical
properties depending on the arrangement of the atoms allow for the storage of
several bits in a single cell. The researchers present their development in the
journal Nature Photonics
(10.1038/nphoton.2015.182).
Light determines the future of information and communication
technology: With optical elements, computers can work more rapidly and more
efficiently. Optical fibers have long since been used for the transmission of
data with light. But on a computer, data are still processed and stored
electronically. Electronic exchange of data between processors and the memory
limits the speed of modern computers. To overcome this so-called von Neumann
bottleneck, it is not sufficient to optically connect memory and processor, as
the optical signals have to be converted into electric signals again.
Scientists, hence, look for methods to carry out calculations and data storage
in a purely optical manner.
Scientists of KIT, the University of Münster, Oxford
University, and Exeter University have now developed the first all-optical,
non-volatile on-chip memory. "Optical bits can be written at frequencies
of up to a gigahertz. This allows for extremely quick data storage by our
all-photonic memory," Professor Wolfram Pernice explains. Pernice headed a
working group of the KIT Institute of Nanotechnology (INT) and recently moved
to the University of Münster. "The memory is compatible not only with
conventional optical fiber data transmission, but also with latest processors,"
Professor Harish Bhaskaran of Oxford University adds.
The new memory can store data for decades even when the
power is removed. Its capacity to store many bits in a single cell of a
billionth of a meter in size (multi-level memory) also is highly attractive. Instead
of the usual information values of 0 and 1, several states can be stored in an
element and even autonomous calculations can be made. This is due to so-called
phase change materials, novel materials that change their optical properties
depending on the arrangement of the atoms: Within shortest periods of time,
they can change between crystalline (regular) and amorphous (irregular) states.
For the memory, the scientists used the phase change material Ge2Sb2Te5 (GST).
The change from crystalline to amorphous (storing data) and from amorphous to
crystalline (erasing data) is initiated by ultrashort light pulses. For reading
out the data, weak light pulses are used.
Permanent all-optical on-chip memories might considerably
increase future performance of computers and reduce their energy consumption.
Together with all-optical connections, they might reduce latencies.
Energy-intensive conversion of optical signals into electronic signals and vice
versa would no longer be required.
Story Source:
The above post is reprinted from materials provided by Karlsruher
Institut für Technologie (KIT).
Note: Materials
may be edited for content and length.
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