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All-dielectric Nanophotonics

Metallic nanoparticles have raised a huge interest from a wide scientific community due to their ability to resonantly interact with light. The resonant interaction is due to the excitation of localized surface plasmon resonances based on a collective oscillation of electrons in the conduction band. Besides metals, dielectric particles can also resonantly interact with light. This kind of resonance is classically called Mie resonance. Whispering gallery modes are very well known high order resonances that can be observed for example in silica microspheres. By increasing the optical contrast between the material and its surrounding, it is possible to excite low order Mie resonances, typically dipolar or quadrupolar modes that can be of electric or magnetic nature. Semi-conductors such as silicon are particularly convenient to design Mie resonators.

The field of optically resonant dielectric particles is a rapidly emerging research field with a large potential technological impact. First, dielectrics feature less losses than metals. Second, silicon is a very abundant, cost effective and non-polluting material. Third, silicon is compatible with CMOS processing.

Promoting magnetic decay rates with silicon based antennas. Decay rates of an electric (red) or magnetic (black) dipolar emitter coupled with a silicon particle [Rol12]. Spontaneous decay rates : The Clarte team started to work on this field of resonant light interaction with high refractive dielectrics in 2010 by considering particles made of titania [Dev10]. Members of the group were first interested by the coupling between quantum emitters and dielectric particles. They investigated both the gain in emission directivity and spontaneous decay rates. In particular, they showed in 2012 the interest of exciting electric and magnetic modes to boost the gain in directivity and also derived the analytic expressions of the electric and magnetic decay rates [Rol12, Rolly12]. In 2015, they used the theory of quasi-normal modes to calculate the Purcell factor of silicon particles homogeneously doped with quantum emitters [Zam15].

Dielectric gap antennas : The strong magnetic resonance featured by subwavelength sized resonators opens new routes to enhance light matter interactions via the magnetic field. Our group demonstrated theoretically and experimentally the ability of dielectric particles to enhance the magnetic field by more than 2 orders of magnitude in the gap separating two particles. Experiments were performed in hyperfrequencies [Bou14].
Silicon particles feature also the ability to strongly enhance the electric field at nanometer scales. In 2016, a team of researchers designed, fabricated and characterized all-silicon nanogap antennas to detect individual fluorescent molecules (collaboration between ICFO (Barcelona), INSP (Paris), Institut Langevin (Paris), CINAM and Institut Fresnel in Marseille). The huge decrease of the detection volume permitted to detect individual molecules even at micromolar concentrations [Reg16].
Silicon nanogap antenna. (Left) Sketch of the experiment. (Right) SEM image of the antenna [Reg16].

Structural colours & all-dielectric metasurfaces : All-dielectric metasurfaces are very interesting to control the field polarization, to engineer the phase of laser beams or also to design ultrathin light mirrors [Bon15]. In 2016, researchers of the team, in collaboration with colleagues from INSP-Paris (B. Gallas) and CINAM-Marseille (F. Bedu and I. Ozerov) imprinted a Mondrian’s painting (Composition in red, blue and yellow) in a silicon film coated on a transparent substrate. The key idea is to nanostructure the film to form arrays of silicon nanocylinders and to control the scattering or extinction spectrum of each particle through its size and shape. The visualized colour depends on the spectrum of the scattered light and is characterized by the three RGB parameters [Proust16]. We also worked on the design, fabrication and characterization of anti-reflective surfaces [Pro15].
All-dielectric structural colour printing. (Left) Original Mondrian's painting. (Right) Reproduction with silicon particles on a transparent substrate. The colour is controlled by the diameter of the particles.

References :
[Proust16] J. Proust, F. Bedu, B. Gallas, I. Ozerov, N. Bonod, “All-Dielectric Structural Colour Printing based on Electric and Magnetic Mie Resonances,” ACS Nano 10, 7761–7767 (2016)

[Reg16] R. Regmi, J. Berthelot, P. M. Winkler, M. Mivelle, J. Proust, F. Bedu, I. Ozerov, T. Begou, J. Lumeau, H. Rigneault, M. F. García-Parajó, S. Bidault, J. Wenger, N. Bonod, “All-Dielectric Silicon Nanogap Antennas to Enhance the Fluorescence of Single Molecules,” Nano Lett. 16, 5143−5151 (2016)

[Zam16] X. Zambrana-Puyalto, N. Bonod, “Tailoring the chirality of light emission with spherical Si-based antennas,” Nanoscale 8, 10441-10452 (2016)

[Pro16] J. Proust, A.-L. Fehrembach, F. Bedu, I. Ozerov, N. Bonod, “Optimized 2D array of thin silicon pillars for efficient antireflective coatings in the whole visible spectrum,” Sci. Rep. 6, 24947 (2016)

[Dev15] A. Devilez, X. Zambrana-Puyalto, B. Stout, N. Bonod, “Mimiking localized surface plasmons with dielectric particles,” Phys. Rev. B 92, 241412(R) (2015)

[Zam15] X. Zambrana-Puyalto, N. Bonod, “Purcell factor of spherical Mie resonators,” Phys. Rev. B 91, 195422 (2015)

[Pro15] J. Proust, F. Bedu, S. Chenot, I. Soumahoro, I. Ozerov, B. Gallas, R. Abdeddaim, N. Bonod, “Chemical alkaline etching of silicon Mie particles,” Adv. Opt. Mat 3, 1280–1286 (2015)

[Bon15] N. Bonod, “Silicon photonics : Large-scale dielectric metasurfaces,” Nature Mat. 14, 664-665 (2015)

[Abb14] M. Abbarchi, M. Naffouti, B. Vial, A. Benkouider, L. Lermusiaux, L. Favre, A. Ronda, S. Bidault, I. Berbezier, N. Bonod, “Wafer scale formation of monocrystalline silicon-based Mie resonators via SOI dewetting,” ACS Nano 8, 11181–11190 (2014)

[Bou14] G. Boudarham, R. Abdeddaim, N. Bonod, “Enhancing the magnetic field intensity with a dielectric gap antenna," Appl. Phys. Lett. 104, 021117 (2014)

[Rolly12] B. Rolly, B. Stout, and N. Bonod, "Boosting the directivity of optical antennas with magnetic and electric dipolar resonant particles," Opt. Express 20, 20376-20386 (2012)

[Rol12] B. Rolly, B. Bebey, S. Bidault, B. Stout, N. Bonod, “Promoting Magnetic Dipolar Transition in Trivalent Lanthanide Ions with Lossless Mie Resonances,” Phys. Rev. B 85, 245432 (2012)

[Dev10] A. Devilez, B. Stout, N. Bonod, “Compact Metallo-dielectric Optical Antenna For Ultra Directional and Enhanced Radiative Emission,” ACS Nano 4, 3390–3396 (2010)