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 beamline 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 thinfilm 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 technical highlight at:
http://www-ssrl.slac.stanford.edu/ research/highlights_archive/photoluminescent_er.html