Amplifying plasmonic signals in dielectric-loaded metallic nanostructures

• Main Author: Bolger, Pádraig Michael
• Published: Queen's University Belfast 2011
• Subjects: 530.44
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.554338

Recent advances in research in the areas of Plasmonics have paved the way for the development of numerous passive plasmonic components capable of field confinement and enhancement. The next step is the integration of active materials within plasmonic structures for light control. One of the main problems with plasmonic devices is a propagation loss associated with Ohmic losses in the metal. The focus of this work is directed at the interaction of surface plasmons with active materials (semi-conductor quantum dots) on the surface of nanostructured metal films, and how to use it to achieve amplification of plasmonic signals. Up to sixteen-fold enhancement of the emission is shown by the coupling of the quantum dot excitons to Bloch modes of the plasmonic crystals in the high gain regime while a more modest gain of 80% enhancement is achieved for the low gain regime. This also allows us to achieve angular control over quantum dot emission. The modulation of the gain medium provides an opportunity to control the transmission of the plasmonic crystal that is similar to the reduction of the Ohmic loss effects on the optical properties of the crystal. An increase in the transmission by about 8 times in the high-gain regime and about 7% in the low gain regime has been observed. Amplified spontaneous emission of surface plasmon polaritons propagating on the metal inetrface with the gain medium has been demonstrated with completely narrowed line- width at a low light intensity of about 5 W/cm2. The achievable gain allows one to achieve approximately a 30% increase of the propagation length of SPPs on a metal/active- polymer interface. The results from this work form a basis for further developments in active plasmonics, primarily to amplify and provide all-optical control of plasmonic signals, both of which are imperative for future plasmonic applications.