Near-field hyper-spectral imaging of resonant Mie modes in a dielectric island

Abstract

All-dielectric sub-micrometric particles have been successfully exploited for light management in a plethora of applications at visible and near-infrared frequencies. However, the investigation of the intricacies of the Mie resonances at the sub-wavelength scale has been hampered by the limitations of conventional near-field methods. In this paper, we address the spatial and spectral mapping of multipolar modes of a Si island by hyper-spectral imaging. The simultaneous detection of several resonant modes allows us to clarify the role of the substrate and the incidence angle of the impinging light, highlighting spectral splitting of the quadrupolar mode and resulting in different spatial features of the field intensity. We explore theoretically and experimentally such spatial features. Details as small as 200 nm can be detected and agree with simulations based on the finite difference time domain method. Our results are relevant to near-field imaging of dielectric structures, the comprehension of the resonant features of sub-micrometric Mie antennas, beam steering, and the resonant coupling with light emitters. Our analysis suggests a novel approach to control the absorption of a single emitter in the framework of surface enhanced absorption or stimulated emission applications.

Probing Inherent Optical Anisotropy in Substrates via Direct Nanoimaging of Mie Scattering

“…Forward scattering in Mie scattering occurs very strongly, whereas backward scattering is relatively weak and the near electromagnetic field distribution is strongly dependent to the size of the particle with respect to the wavelength. Additionally, Mie scattering is influenced by the shape of the particles, with nonspherical or heterogeneous particles exhibiting complex variations in scattering intensity and direction. , Since Mie scattering is exceedingly sensitive to geometric factors, the environmental substrate may break the symmetry of the scattering pattern, especially in the case of the inherently anisotropic substrate. To exploit these phenomena, we conducted direct optical imaging of Mie scattering in various configurations with different substrates and incident wavevectors, as illustrated in Figure b.…”

Light Emitting Si‐Based Mie Resonators: Toward a Huygens Source of Quantum Emitters

“…Fabrication of Si resonant antennas via dewetting [ 39–41,43 ] and the characterization of their optical properties under white light illumination have been extensively addressed in the past few years, and we thus refer the reader to the existing literature. [ 42,44 ] The nano‐fabrication was performed following these steps (Figure 1): 1)Starting from a 125 nm thick silicon on insulator wafer (UT‐SOI) atop 2 µm buried oxide (BOX), we progressively thinned the UT‐SOI via thermal oxidation in a rapid thermal processor leaving at the end of the process a 20 nm Si layer atop the BOX. The thermal oxide formed on the UT‐SOI was removed via chemical etching in HF solution. 2)By patterning the UT‐SOI via low‐resolution (≈2 µm) photolithography and plasma etching, we formed µm sized, UT‐SOI patches (Figure 1a, top panel).…”

“…The investigated samples host arrays of resonators spaced a few microns from each other. [42,44] Different spacing corresponds to different average island size. Thus, on each sample we investigate arrays of nominally identical resonators extending over about 50 µm × 50 µm, having bases and heights ranging between ≈280 nm to ≈770 nm and ≈80 nm to ≈200 nm, respectively.…”

“…This feature (about 20 nm height) does not significantly modify the optical properties of the islands. [42,44] 4) After island formation, carbon ions are implanted using various beam energies. By changing the energy of the implant we set different depths beneath the surface of the resonators at which G-centers will form (Figure 2a).…”

Security labeling and optical information encryption enabled by laser-printed silicon Mie resonators

“…The hemispherical Si NPs on a glass substrate can be considered as an optically resonant nanostructure supporting electric-and magnetic-type Mie resonances, 37,44,45 similarly to the widely studied high-index spherical-shaped NPs 46 or lithography-fabricated micro-disks. 36,47 The resonant behaviour of the hemispherical NPs in the visible spectral range is dominated by spectrally overlapping electric and magnetic dipolar modes as was previously discussed in ref.…”