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March 2015 • The PCB Magazine 19 2. Fire Research Station, UK 1993. 3. Fire Engineering ® . Glenn A. Gaines, Dep- uty U.S. Fire Administrator. 4. Paul Farley in Furniture News, Jan 29, 2014. 5. Dr. Oliver Töpfer, Nabaltec. "Boehmite as Halogen Free Flame Retardant Filler Utilized in Cost Effective Producton of Highly Reliable Base Laminates," EIPC Summer Conference, Milan, September 2012. 6. International Electrotechnical Commis- sion IEC 61249-2-21. 7. Risks and Benefits in the Use of Flame Re- tardants in Consumer Products, G C Stevens & A H Mann, University of Surrey: DTI Reference URN 98/1026, 8. Bromine Science and Environmental Forum, 9. Candidate List of Substances of Very High Concern for Authorisation, 10. Courtesy of the European Flame Retar- dants Association (EFRA). 11. National Electrical Manufacturers Asso- ciation (NEMA) LI 1-1998. 12. FR-4 Reclassification: An Update. Emma Hudson. Proceedings of EIPC Winter Confer- ence, Geneva January 2014. alun Morgan is chairman of the European Institute of printed Circuits. FIRE RETARDANCy: WHAT, WHy, AND HOW continues Feature Metamaterials—artificial nanostructures en- gineered with electromagnetic properties not found in nature—offer tantalizing future pros- pects such as high resolution optical micro- scopes and superfast optical computers. To real- ize the vast potential of metamaterials, however, scientists will need to hone their understanding of the fundamental physics behind them. This will require accurately predicting nonlinear op- tical properties—meaning that interaction with light changes a material's properties, for exam- ple, light emerges from the material with a dif- ferent frequency than when it entered. help has arrived. Scientists with the u.S. Department of Energy (DOE)'s Lawrence Berkeley national Labora- tory (Berkeley Lab) and the university of California (uC) Berkeley have shown, using a recent theory for nonlinear light scattering when light passes through nanostructures, that it is possible to predict the non - linear optical properties of metamaterials. "The key question has been whether one can determine the nonlinear behavior of meta- materials from their exotic linear behavior," says xiang Zhang, director of Berkeley Lab's Materials Sciences Division and an internation- al authority on metamaterial engineering who led this study. "we've shown that the relative nonlinear susceptibility of large classes of meta- materials can be predicted using a comprehen- sive nonlinear scattering theory. This will al- low us to efficiently design metamaterials with strong nonlinearity for important applications such as coherent raman sensing, entangled photon generation and frequency conversion." Zhang, who holds the Ernest S. Kuh Endowed Chair at uC Berkeley and is a mem- ber of the Kavli Energy nanoSciences Institute at Berkeley (Kavli EnSI), is the corresponding author of a paper describing this research in the journal nature Mate- rials. The paper is titled "predicting nonlinear prop- erties of metamaterials from the linear response." The other authors are Kevin O'Brien, haim Suchowski, Junsuk rho, alessandro Salandrino, Boubacar Kante and xiaobo Yin. Predicting Metamaterial Nonlinear Optical Properties