Fabrication of nanostructures for photonic applications
Résumé
Nanophotonics requires a very fine control over the size and shape of nanofeatures because they strongly affect all the types of light-matter interactions. The most efficient interactions occur when the light wavelength is resonant with the spectral response of the individual particles or with coupling between the particles if they are situated close enough from each other. We will discuss the fabrication of metal and dielectric metasurfaces using both individual and collective effects for photonic applications. All nanostructures were realized in our clean room facilities using nanofabrication tools such as electron beam lithography, magnetron sputtering or thermal evaporation and chemical or reactive ion etching. We will illustrate the discussion on nanofabrication process equipment available in the CINaM clean room PLANETE by new scientific results.
First, nanostructured metasurfaces using plasmon resonances in individual gold discs were fabricated on glass substrates and were used for precise relative humidity sensing [1] and for the studies of interactions between water vapor and sooth aerosols [2] in collaboration with Benjamin Demirdjian (CINaM, Marseille). Localized plasmons in individual gold discs or more complex nanostructures organized in a periodic metamaterial lattices can also be resonantly coupled to a diffraction wave under certain excitation conditions [3]. Such a coupling leads to a drastic narrowing of plasmon resonance lineshapes in direct and ATR geometries observed by collaborators from two research groups leaded by Andrei Kabashin (LP3, Marseille) and by Alexander Grigorenko (Manchester). Such plasmonic surface lattice resonances are very promising for the improvement of performance of plasmonic biosensors [4]. Even more complex spiral antenna structures organized in metasurfaces were fabricated and studied in collaboration with the group of Jeong Weon Wu (EWHA University, Korea) in order to control vortex-charge dependent separation of structured light beams [5].
The second type of nanostructures that we will discuss are individual silicon Mie resonators and all-dielectric metasurfaces obtained in collaboration with Institut Fresnel (Marseille) and Institut de NanoSciences de Paris. Such nanoparticles made of high-refractive index dielectric materials like silicon are known to efficiently scatter incident electromagnetic waves. Their optical spectra show several well pronounced peaks corresponding to electric and magnetic dipole and quadrupole moments resonantly induced in the particles by the incident light. For the visible and near-infrared spectral regions, the typical sizes of individual resonant silicon particles are situated in the range from 70 to 250 nm. These nanostructures were fabricated using electron beam lithography followed by wet chemical alkaline etching [6] or reactive ion etching [7].
For the metasurfaces constituted by the individual particles, the distances between them should be large enough in order to avoid possible near-field coupling. For example, in collaboration with the group of Nicolas Bonod (Institut Fresnel, Marseille) we have fabricated the metasurfaces composed of amorphous silicon particles situated at distances larger than 1 µm providing vivid structural colors [6]. The relative strength of the electric and magnetic resonances can be easily tuned with the aspect ratio of the particle. This allowed us to create a large palette of colors when considering the same particle height and simply tuning the aspect ratio of the particle by varying the diameter [6,7].
We also fabricated individual silicon monomers and dimers that were used to tailor the spontaneous emission of organic molecules. The monomer silicon optical nanoantennas were used by the groups leaded by Sébastien Bidault and Yannick de Wilde (Institut Langevin, Paris) to enhance the spontaneous emission rate and brightness of solid-state emitters [8]. Using scanning probe microscopy, they analyzed in three dimensions the near-field interaction between a 100 nm fluorescent nanosphere and silicon nanoantennas and demonstrated significant enhancement and inhibition of the fluorescence intensity depending on the size of the antennas and the distance between the near-field probe and monomer antennas. When the antennas are constituted of two silicon disks separated by a gap of several nanometers, fluorescence correlation spectroscopy and lifetime measurements performed in the group of Jérôme Wenger (Institut Fresnel, Marseille) demonstrate that the fluorescence intensity of dye molecules in the gap can be enhanced by more than two orders of magnitude [9]. These results confirm that all-silicon nanoantennas can be considered as a valid alternative to plasmonic devices.
Finally, a metasurface composed of closely packed resonators has shown to be a very efficient antireflective coating in a large spectral range from the visible to the near infrared and it was fabricated by nanostructuring of monocrystalline silicon [10]. Angle resolved and polarized optical measurements performed in the group of Nicolas Bonod showed that the light reflection was remaining under 5% when averaged in the visible spectrum for both polarizations in a wide angular range. Light reflection remained almost insensitive to the light polarization even in oblique incidence.
In conclusion, we show that common nanofabrication tools and processes (e-beam lithography, evaporation, sputtering, chemical and reactive ion etching) are well adapted for realization of objects for fundamental studies and for nanophotonic applications.
[1] B. Demirdjian, F. Bedu, A. Ranguis, I. Ozerov, and C.R. Henry, “Water adsorption by a sensitive calibrated gold plasmonic nanosensor”, Langmuir 34, 5381 (2018)
[2] B. Demirdjian, F. Bedu, A. Ranguis, I. Ozerov, A. Karapetyan, and C.R. Henry, “Indirect nanoplasmonic sensing to probe with a high sensitivity the interaction of atmospheric water with soot aerosols”, J. Phys. Chem. Lett. 6, 4148 (2015)
[3] A. Danilov, G. Tselikov, F. Wu, V.K. Kravets, I. Ozerov, F. Bedu, A.N. Grigorenko and A.V. Kabashin, “Condition of excitation and sensitivity of diffractively-coupled surface lattice resonances over plasmonic nanoparticle arrays in ATR geometry”, Proc. SPIE, 10521, 1052109 (2018)
[4] A. Danilov, G. Tselikov, F. Wu, V.K. Kravets, I. Ozerov, F. Bedu, A.N. Grigorenko and A.V. Kabashin, “Ultra-narrow surface lattice resonances in plasmonic metamaterial arrays for biosensing applications”, Biosensors and Bioelectronics 104, 102 (2018)
[5] Y.U. Lee, I. Ozerov, F. Bedu, J.S. Kim, F. Fages, and J.W. Wu, “Extrinsic spin-and orbital-Hall effect in cyclic group symmetric metamaterial”, Proc. SPIE 9918, 991818 (2016)
[6] J. Proust, F. Bedu, S. Chenot, I. Soumahoro, I. Ozerov, B. Gallas, R. Abdeddaim, and N. Bonod, “Chemical alkaline etching of silicon Mie particles”, Advanced Optical Materials 3, 1280 (2015)
[7] J. Proust, F. Bedu, B. Gallas, I. Ozerov, and N. Bonod, “All-Dielectric Colored Metasurfaces with Silicon Mie Resonators,” ACS Nano 10, 7761 (2016)
[8] D. Bouchet, M. Mivelle, J. Proust, B. Gallas, I. Ozerov, M.F. García-Parajó, A. Gulinatti, I. Rech, Y. de Wilde, N. Bonod, V. Krachmalnicoff, and S. Bidault, “Enhancement and Inhibition of Spontaneous Photon Emission by Resonant Silicon Nanoantennas,” Phys. Rev. Applied 6,064016 (2016)
[9] 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, and N. Bonod, “All-Dielectric silicon nanogap antennas to enhance the fluorescence of single molecules,” Nano Lett. 16, 5143 (2016)
[10] J. Proust, A-L. Fehrembach, F. Bedu, I. Ozerov, and N. Bonod, “Optimized 2D array of thin silicon pillars for efficient antireflective coatings in the visible spectrum”, Scientific Reports 6, 24947 (2016)