Fiber optic communication relies on the strength of a signal of light to
deliver information, but over long distances that signal becomes dim and can
lose its integrity. Amplifying the signal along the way can decrease signal
loss, and scientists have been searching for new materials to build photonic
signal amplifiers that are inexpensive and easily mass produced. Now,
researchers from UCLA, working in part at the Stanford Synchrotron Radiation
Laboratory Beam Line 11-2, have demonstrated how to deposit a special thin film
with photoluminescent erbium (Er) onto silicon wafers. This technique could
lead to the development of miniaturized optical amplifiers integrated with
microchips for their incorporation into communications hardware.
Positively charged
Er3+ is known for its ability to photoluminesce, which is a similar
phenomenon at work in glow-in-the-dark paint. Previous research has shown that
ionic Er incorporated in silica loses its reactivity to light, and until now
researchers had no way to prevent this. Using Extended X-ray Absorption Fine
Structure (EXAFS), the UCLA team showed that ions of Er must be deposited at a
very specific concentration and in a certain arrangement, or the ions begin to
interact with each other and cancel out the photoluminescent effect.
By doping 8 atom% ionic Er into
Y2O3 thin films by atomic layer deposition, the Er ions
remain sufficiently distant from each other to retain their photoluminescent
properties. This percentage also assures that enough Er is incorporated into
the thin film to have a strong amplifying effect.
The results of this study are published in Journal of Applied Physics. (T.T.
Van, Bargar, J.R., and Chang, J.P. (2006) Structural investigation of Er
coordination in Y2O3. J. Applied Physics 100, 023115)
To learn more about this research see the full scientific highlight at:
http://www-ssrl.slac.stanford.edu/
research/highlights_archive/erdopedy2O3.html
