By G.P. Thomas
Researchers from the Duke University and Imperial College have devised a method to measure photonic interactions at the atomic scale using which the upper performance limit of light enhancing metal devices can be determined.
Plasmonic System (Credit: Sebastian Nicosia and Cristian Ciracì)
Such devices which incorporate metals at the nanoscale for light enhancement are known as plasmonic devices and the field of study is labeled plasmonics. This is a reference to plasmons, which are high energy electrons excited by light. The plasmons induce enhancement of the electromagnetic field. This electromagnetic field enhancement is superior in nanoscale metals than that facilitated by any other material.
A light enhancing device’s performance limit has until now been difficult to determine owing to the inability to measure photonic interaction at small scales. The interactions typically occur between two metal particles located at a particular distance from each other. Researchers have been trying in vain in the last few decades to determine the effect of bridging the gap between the metal particles to nanoscale. The technique developed by Duke University researchers to quantify atomic scale photonic interactions equips them with information about the method to control scattering of light in order to develop effective photonic devices. The researchers started their work with a system comprising ultra-thin layer of organic molecule coating on thin gold film interspersed with carbon chains that are precisely controllable. The top of the monolayer was covered with gold nanospheres. The researchers were thus able to achieve a spacing of one atom thick between the gold nanospheres and gold film. The knowledge of maximum possible enhancement equips the researchers with an ability to determine the efficiency of any plasmonic system and also enables them to tune the plasmonic systems to provide required enhancements.