Dielectric nano-antennas for visible light. Negligible losses in gallium phosphide

J. CAMBIASSO; E. CORTÉS; A. RAKOVICH; G. GRINBLAT; Y. LI; S. A. MAIER

Encuentro; The 6th International Topical Meeting on Nanophotonics and Metamaterials; 2017

Manipulating light in the visible wavelength regime without any optical loss is challenging. Although plasmonic metallic nano-antennas have been demonstrated to operate in the visible, they suffer from the notorious disadvantage of being abundantly lossy [1]. The loss mechanisms are widely known [1] and are related to different scattering processes from the externally excited surface plasmon polaritons (SPPs) into phononic modes, excitonic modes, hot-carrier generation, Ohmic heating, etc. In this context, alternatively, dielectric antennas [2] have been proposed due to their intrinsic low-loss properties. For instance, using Si as the quintessential dielectric material, nanoantennas have been shown to control magnetic and electric dipolar transitions at near-infrared wavelengths [3]. Unfortunately, Si nanoantennas cannot extend their impact into the visible range as the absorption starts dominating over scattering. On the other hand, gallium phosphide (GaP) has a negligible imaginary refractive index in the visible, and so its use in dielectric antennas should notably expand their functional/practical spectral range [4]. It has been shown that GaP nanoparticle-dimers do not heat appreciably the environment in which other nano-objects like quantum dots, molecules, or nanoparticles can be localised to interact with the structure [5]. Furthermore, confinement at the nanoscale creates enhanced electric and magnetic fields that can be exploited for higher-harmonic generation [6], surface enhanced Raman scattering or to probe light-matter interaction in the visible. In this work, we will review various aspects and challenges that the use of GaP antennas present. A figure of merit defined as scattered cross-section over extinction cross-section yields values over 90%, indicating that most of the incident power is efficiently scattered into the far-field. The preliminary results presented here open the way to negligible-loss nanophotonics in the optical regime with applications in non linear and quantum optics. References [1] Khurgin, J. B., "How to deal with the loss in plasmonics and matamaterials", Nat. Nano 10 (2015). [2] Albella, .P., Ameen Poyli, M., Schmidt, M. K., Maier, S. A., Moreno, F., Sáenz, J. J., Aizpurua, J., "Low-loss electric and magnetic field-enhancement spectroscopy with subwavelength silicon dimers", J. Phys. Chem. C 117 (2013); Caldarola, M., Albella, P., Cortés, E., Rahmani, M., Roschuk, T., Grinblat, G., Oulton, R. F., Bragas, A. V. and Maier, S. A., "Non-plasmonic nanoantennas for suface enhanced spectroscopies with ultra-low heat conversion", Nat. Comm. 6 (2015). [3] Schmidt, M. K., Esteban, R., Sáenz, J. J., Suárez-Lacalle, I., Mackowski, S., Aizpurua, J., "Dielectric antennas: a suitable platform for controlling magnetic dipolar emission", Opt. Exp. 20 (2012). [4] Albella, P., Alcaraz de la Osa, R., and Moreno, F., and Maier, S. A., "Electric and magnetic field enhancement with ultralow heat radiation dielectric nanoantennas: considerations for surface enhanced spectroscopies", ACS Phot. 1 (2014). [5] Krasnok, A. E., Miroshnickehcnko, A. E., Belov, P. A., Kivshar, Y. S., "All-dielectric optical nanoantennas", Opt. Exp. 20 (2012). [6] Sanatinia, R., Anand, S., Swillo, M., "Modal engineering of second-harmonic generation in single GaP nanopillars", Nano Lett. 14 (2014).