Nano-antennas, phased arrays, plasmon lattice lasers

Nano-antennas, phased arrays, plasmon lattice lasers

Most of the sources of light that nature provides are electronic transitions in atoms and molecules. This means that elementary emitters of photons are by themselves deeply subwavelength in size, almost pointlike. As consequences single quantum emitters are not very bright, and their emission is not very directional. Techniques to make quantum emitters emit more light per unit of time, and to make them do so in just one preferred spatial mode generally rely on narrowband dielectric microcavities, or on plasmon nano-antennas that provide strong field enhancement.

In our work we mainly focus on using plasmon antennas as elements in “phased arrays” for their strong scattering: metal particles provide very large polarizability in a small volume, and thereby very large resonant scattering cross sections. When cleverly arranged, oligomers of such strongly scattering particles will make emitters radiate in a strongly directive fashion. The physics is that a single driving emitter will excite plasmon resonances in all the antenna particles around it, which also can strongly drive each other. The net effect can be that the induced currents in all the antenna particles will constitute a strongly directional source by interference that is controlled through geometry. The most famous example is the plasmon Yagi-Uda antenna.

Our interest covers several aspects of phased array antennas. In fluorescence microscopy, a substrate that makes single fluorophores emit more light in a low NA is highly desirable. We have worked on phased-array antenna substrates for bright and directional emission that enhance collection efficiencies by up to two orders of magnitude. In the context of solid-state lighting, phased-array antennas embedded in phosphor layers can improve the conversion of blue LED light to a bright and directed white. The requirement is that the loss inherent in metal is minimized, to maintain high internal quantum efficiency, while beaming light. Together with the group of Rivas at DIFFER, we study plasmon lattice structures for fluorescence, and for lasing. As plasmon lattice lasers, we study 2D organic waveguides with gain, in which periodic plasmon lattices are embedded. These structures are on par with organic DFB lasers in terms of threshold, but remarkably robust against disorder, and remarkably flexible in terms of re-arranging the phased array into quasiperiodic, aperiodic and even randomized structures.

Figure: light from a 2D waveguide that is usually radiated isotropically can be funneled preferentialy into particular directions, for instance by using a square array of plasmon particles. When pumped hard enough, fluorescence enhancement turns to lasing.

See:

[87] M. Cotrufo, C. I. Osorio, and A. F. Koenderink, Spin-Dependent Emission from Arrays of Planar Chiral Nanoantennas Due To Lattice and Localized Plasmon Resonances, ACS Nano 10, 3389–3397, (2016). (p)reprint DOI
[84] D. K. G. de Boer, M. A. Verschuuren, K. Guo, A. F. Koenderink, J. G. Rivas, and S. R.-K. Rodriguez, Directional Sideward Emission from Luminescent Plasmonic Nanostructures, Optics Express 24, A388–A396, (2016). (p)reprint DOI
[79] L. Langguth, A. H. Schokker, K. Guo, and A. F. Koenderink, Plasmonic Phase-Gradient Metasurface for Spontaneous Emission Control, Phys. Rev. B 92, 205401, (2015). (p)reprint DOI
[77] A. H. Schokker and A. F. Koenderink, Statistics of Randomized Plasmonic Lattice Lasers, ACS Photonics 2, 1289–1297, (2015). (p)reprint DOI
[76] F. B. Arango, R. Thijssen, B. Brenny, T. Coenen, and A. F. Koenderink, Robustness of Plasmon Phased Array Nanoantennas to Disorder, Sci. Rep. 5, 10911, (2015). (p)reprint DOI
[70] A. Mohtashami, T. Coenen, A. Antoncecchi, A. Polman, and A. F. Koenderink, Nanoscale Excitation Mapping of Plasmonic Patch Antennas, ACS Photonics 1, 1134–1143, (2014). (p)reprint DOI
[63] L. Langguth, D. Punj, J. Wenger, and A. F. Koenderink, Plasmonic Band Structure Controls Single-Molecule Fluorescence, ACS Nano 7, 8840–8848, (2013). (p)reprint DOI
[46] M. Frimmer, T. Coenen, and A. F. Koenderink, Signature of a Fano Resonance in a Plasmonic Metamolecule’s Local Density of Optical States, Phys. Rev. Lett. 108, 077404, (2012). (p)reprint DOI
[43] T. Coenen, E. J. R. Vesseur, A. Polman, and A. F. Koenderink, Directional Emission from Plasmonic Yagi-Uda Antennas Probed By Angle-Resolved Cathodoluminescence Spectroscopy, Nano Lett. 11, 3779–3784, (2011). (p)reprint DOI