Nitrogen dioxide couples light and matter more efficiently
Researchers from the Surface Photonics group of FOM Institute AMOLF, together with colleagues from Holst Center IMEC, have demonstrated that it is possible to actively influence how light captured in an organic material interacts with a superficial polarisation wave in the underlying metal. This could lead to improvements in both chemical and biological sensors. The research results were published on 28 July in the journal ACS Nano.
Light captured in an organic material gives rise to excitons: excited electron-hole pairs in the organic material. Surface plasmon polaritons are the associated oscillations of electrons on the surface of a metal. Active control of the coupling between these two is achieved by adding a reactive gas to the organic layer. When nitrogen dioxide molecules react with the organic molecules, the 'strength' of the excitonic layer increases; therefore, the coupling strength of these excitons to surface plasmon polaritons in a gold film beneath the organic layer increases as well. As this interaction is reversible, this offers a versatile approach to regulating the degree of coupling between light and matter.
The possibility of being able to give a system a certain degree of coupling has both fundamental consequences and practical applications. From a fundamental viewpoint, this control will provide a better quantitative understanding of the coupling than was previously possible for such systems. From a more practical perspective, it has been demonstrated that the coupling has consequences for the velocity of surface plasmon polaritons.
Contact
Audrey Berrier or Jaime Gómez Rivas, FOM Institute AMOLF, p.a. Philips Research Laboratories Eindhoven, High Tech Campus 4, 5656 AE Eindhoven, Tel. +31 (0)40 274 23 49.
Reference
'Active Control of the Strong Coupling Regime between Porphyrin Excitons and Surface Plasmon Polaritons',
Audrey Berrier; Ruud Cools; Christophe Arnold; Peter Offermans; Mercedes Crego-Calama; Sywert Brongersma; Jaime Gómez-Rivas
ACS Nano (2011), doi: 10.1021/nn201077r