With the advent of two-dimensional (2D) materials and their extraordinary optical properties, during the last years first visualizations of both low-loss and electrically tunable plasmons in graphene [1,2] and high optical quality phonons in monolayer and multilayer h-BN nanostructures have been shown in the mid-infrared spectral range, thus introducing a very encouraging arena for scientifically ground-breaking discoveries in the field of nano-optics. Indeed, first proof-of-concept devices permitting to control the propagation of graphene plasmons, such as a lens and a prism, have been demonstrated [3]. Importantly, these initial achievements were possible by the development of an innovative optical scheme in scattering-type near-field optical microscopy (s-SNOM), so far the only tool that allows for imaging 2D plasmons in real space [4]. Inspired by this unique capability and the extraordinary prospects given by our initial experiments, we aim in the next years to develop the fields of 2D nanoplasmonics (using graphene plasmons) and nanophononics (using phonon polaritons) to establish a technological platform that, including coherent sources, waveguides, routers, and efficient detectors [5], permits an unprecedented active control and manipulation of light and light-matter interactions on the nanoscale and at room temperature, thus laying the foundations of the field 2D nano-optics [6 ,7].

Advances in this direction will have an enormous scientific importance and technological relevance in a variety of fields such as sensing, optoelectronic information processing, non-linear optics, quantum science, or photochemistry, where active control of fundamental nanoscale light-matter processes are of vital importance.

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References:

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1. J. Chen*, M. Badioli*, P. Alonso-González*, S. Thongrattanasiri*, F. Huth*, J. Osmond, M. Spasenović,  A. Centeno, A. Pesquera, P. Godignon, A. Zurutuza, N. Camara, J. Garcia de Abajo, R. Hillenbrand, and F. Koppens. “Optical nano-imaging of gate-tuneable graphene plasmons”, Nature, 487, pp77-81 (2012).

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2.  A. Woessner, M.B. Lundeberg, Y. Gao, A. Principi, P. Alonso-González, M. Carrega, K. Watanabe, T. Taniguchi, G. Vignale, M. Polini, J. Hone, R. Hillenbrand, and F.H.L. Koppens, “Highly confined low-loss plasmons in graphene–boron nitride heterostructures”, Nature Materials, 14, 421-425 (2015).

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3.  P.Alonso-González, A.Y. Nikitin, F. Golmar, A. Centeno, A. Pesquera, S. Vélez, J. Chen, F. Koppens, A. Zurutuza, F. Casanova, L.E. Hueso, and R. Hillenbrand. “Launching and wavefront-engineering of propagating graphene plasmons with resonant metal antennas”, Science 344, 1369 (2014). 

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4. A. Y. Nikitin, P. Alonso-González, S. Vélez, S. Mastel, A. Centeno, A. Pesquera, A. Zurutuza, F. Casanova, L. E. Hueso, F. H. L. Koppens, and R. Hillenbrand “Real-space mapping of tailored sheet and edge plasmons in graphene nanoresonators”, Nature Photonics, 10 (4), 239, (2016).

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5. P. Alonso-González, A. Y. Nikitin, Y. Gao, A. Woessner, M. B. Lundeberg, A. Principi, N. Forcellini, W. Yan, S. Vélez, A. J. Huber, K. Watanabe, T. Taniguchi, L. E. Hueso, M. Polini, J. Hone, F. H. L. Koppens, and R. Hillenbrand “Acoustic terahertz graphene plasmons revealed by photocurrent nanoscopy”, Nature Nanotechnology, 12 (1), 21, (2017).

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6. W. Ma, P. Alonso-González*, S. Li, A.Y Nikitin, J. Yuan, J. Martín-Sánchez, J. Taboada-Gutiérrez, I. Amenabar, P. Li, S. Vélez, C. Tollan, Z. Dai, Y. Zhang, S. Sriram, K. Kalantar-Zadeh, S-T Lee, R. Hillenbrand*, and Q. Bao* "In-plane anisotropic and ultra-low-loss polaritons in a natural van der Waals crystal"

Nature 562, pp 557-562, (2018).

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7. Javier Taboada-Gutiérrez, Gonzalo Álvarez-Pérez, Jiahua Duan, Weiliang Ma, Kyle Crowley, Iván Prieto, Andrei Bylinkin, Marta Autore, Halyna Volkova, Kenta Kimura, Tsuyoshi Kimura, M-H Berger, Shaojuan Li, Qiaoliang Bao, Xuan PA Gao, Ion Errea, Alexey Y Nikitin, Rainer Hillenbrand, Javier Martín-Sánchez*, Pablo Alonso-González* "Broad spectral tuning of ultra-low-loss polaritons in a van der Waals crystal by intercalation"

Nature Materials 19, 964-968 (2020).

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