{"id":1886,"date":"2010-10-05T17:12:23","date_gmt":"2010-10-06T00:12:23","guid":{"rendered":"http:\/\/cafe.foundation\/blog\/?p=1886"},"modified":"2010-10-05T17:18:32","modified_gmt":"2010-10-06T00:18:32","slug":"a-thousand-fold-point-of-light","status":"publish","type":"post","link":"http:\/\/cafe.foundation\/blog\/a-thousand-fold-point-of-light\/","title":{"rendered":"A Thousand-Fold Point of Light"},"content":{"rendered":"

Shortly after reading of MIT\u2019s 100-fold breakthrough in light-gathering capabilities for solar cells, we saw the news <\/a>about a one-thousand-fold increase claimed by Rice University researchers.\u00a0 Professor of physics and astronomy Doug Natelson announced the findings of his research group, which includes his graduate student Dan Ward, and colleagues in Germany and Spain.<\/p>\n

In his blog<\/a>, Natelson stated, \u201cMy student (with theorist collaborators) had a paper<\/a> published online in Nature Nanotechnology<\/em> yesterday, and this gives me an excuse to talk about using metal nanostructures as optical antennas. The short version: using metal electrodes separated by a sub-nanometer gap as a kind of antenna, we have been able to get local enhancement of the electromagnetic intensity by roughly a factor of a million (!), and we have been able to determine that enhancement experimentally via tunneling measurements.\u201d<\/p>\n

In a brief discussion with this reporter, Natelson deflated any ideas that this technology would be powering up solar cells in the near future.\u00a0 Noting that other researchers, such as those at MIT, have used long filaments as antennas to trap light for longer periods to enhance solar cell performance, he explained that his very specifically-tuned gold nano-antenna works so far in a narrow range, from 700 nanometers to the lower part of the infra-red range of light, and only for a nano-instant.\u00a0<\/p>\n

\u201cWhite light\u201d associated with sunlight has a broad spectrum of wavelengths, and these ranges would have to be investigated in narrow bands with lenses and mirrors optimized for those wavelengths.\u00a0 This time-consuming and costly process would require at least a six-figure grant or beneficent resource to allow characterization of the device\u2019s potential for the broader spectrum of light.<\/p>\n

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The tips "grab the light and concentrate it down into a tiny space," Natelson said, leading to a thousand-fold increase in light intensity in the gap. <\/p><\/div>\n<\/div>\n

When asked about the efficiency of his antenna he stated, \u201cIt\u2019s terrible,\u201d at least partly because of the\u00a0finite nature of the burst of energy released, rather than the long meanders that\u00a0photons take through other collectors.\u00a0\u00a0\u00a0Natelson cautioned that, \u201cBefore we get too excited,\u201d about the potential for creating super-powerful solar collectors, there are possible near-term applications in areas such as\u00a0photochemistry and photocatalysis.\u00a0 In both those\u00a0instances intense bursts of energized light could create photochemical reactions, such as splitting water molecules into oxygen and hydrogen \u2013 bringing us indirectly to another potential energy source.<\/p>\n

In his blog, Natelson explains the lure of exploring these near-quantum areas.\u00a0 “When you think about it, it’s pretty amazing. The radiation intensity in the little nanogap between our electrodes can be hundreds of thousands or millions of times higher than that from the incident laser. Wild stuff, and definitely food for thought.”<\/p>\n