Experimental Investigation of the Thermal Emission Cross Section of Nanoresonators Using Hierarchical Poisson-Disk Distributions.

Effective cross sections of nano-objects are fundamental properties that determine their ability to interact with light. However, measuring them for individual resonators directly and quantitatively remains challenging, particularly because of the very low signals involved. Here, we experimentally measure the thermal emission cross section of metal-insulator-metal nanoresonators using a stealthy hyperuniform distribution based on a hierarchical Poisson-disk algorithm. In such distributions, there are no long-range interactions between antennas, and we show that the light emitted by such metasurfaces behaves as the sum of cross sections of independent nanoantennas, enabling direct retrieval of the single resonator contribution. The emission cross section at resonance is found to be on the order of λ_{0}^{2}/3, a value that is nearly 3 times larger than the theoretical maximal absorption cross section of a single particle, but remains smaller than the maximal extinction cross section. This measurement technique can be generalized to any single resonator cross section, and we also apply it to a lossy dielectric layer.

Helmholtz Resonator Applied to Nanocrystal-Based Infrared Sensing.

While the integration of nanocrystals as an active medium for optoelectronic devices progresses, light management strategies are becoming required. Over recent years, several photonic structures (plasmons, cavities, mirrors, etc.) have been coupled to nanocrystal films to shape the absorption spectrum, tune the directionality, and so on. Here, we explore a photonic equivalent of the acoustic Helmholtz resonator and propose a design that can easily be fabricated. This geometry combines a strong electromagnetic field magnification and a narrow channel width compatible with efficient charge conduction despite hopping conduction. At 80 K, the device reaches a responsivity above 1 A·W-1 and a detectivity above 1011 Jones (3 µm cutoff) while offering a significantly faster time-response than vertical geometry diodes.

High-efficiency second-harmonic generation in coupled nano Fabry-Perot thin resonators.

In this paper we experimentally demonstrate second-harmonic generation (SHG) enhancement in thin 1D periodic plasmonic nanostructures on GaAs in the infrared spectral range. Due to the properly designed coupling of horizontal Fabry-Perot nanoresonators that occurs inside these structures, the obtained conversion efficiencies go up to the 10-7 W-1 range. Moreover, we demonstrate that the engineering of the plasmonic nanoantenna dimensions on the same GaAs layer can lead to SHG enhancement for pump wavelengths ranging from 2.8 µm to 3.3 µm.

Experimental demonstration of second-harmonic generation in high χ2 metasurfaces.

Metasurfaces able to concentrate light at various wavelengths are promising for enhancing nonlinear interactions. In this Letter, we experimentally demonstrate infrared second-harmonic generation (SHG) by a multi-resonant nanostructure. A 100 GaAs layer embedded in a metal-insulator-metal waveguide is shown to support various localized resonances. One resonance enhances the nonlinear polarization due to the transverse magnetic (TM)-polarized pump wavelength near 3.2µm, while another is set near the TE-polarized generated wavelength (1.6µm). The measured SHG efficiency is higher than 10-9W-1 for pump wavelengths ranging from 2.9 to 3.3µm, which agrees with theoretical computations. This is typically 4 orders of magnitude higher than the equivalent GaAs membrane.

4000-enhancement of difference frequency generation in a mode-matching metamaterial.

In the wake of the control of light at the sub-wavelength scale by nanoresonators, metasurfaces allowing strong field exaltations are an attractive platform to enhance nonlinear processes. Recently, high efficiency second harmonic and difference frequency generations were demonstrated in metasurfaces that generate a nonlinear polarization normal to the surface. Here, we introduce a mode matched resonator that is able to produce this particular nonlinear polarization in a layer of gallium arsenide associated with a gold metasurface. The nonlinear conversion mechanism is described as a two-step process in which efficiency is shown to yield a good colocalization and a strong enhancement of the pump fields, as well as a high extraction efficiency of the generated field. This mode-matched metasurface is able to reach a difference frequency generation (DFG) efficiency of 10-2W/W2. This opens a new paradigm where alternative nonlinear materials could be reintroduced in metasurfaces and yields even higher efficiency than high effective χ(2) structures.

High-quality-factor double Fabry-Perot plasmonic nanoresonator.

Fabry-Perot (FP)-like resonances have been widely described in nanoantennas. In the original FP resonator, a third mirror can be added, resulting in a multimirror interferometer. However, in the case of a combination of nanoantennas, it has been reported that each cavity behaves independently. Here, we evidence the interferences between two FP absorbing nanoantennas through a common mirror, which has a strong impact on the optical behavior. While the resonance wavelength is only slightly shifted, the level of absorption reaches nearly 100%. Moreover, the quality factor increases up to factor 7 and can be chosen by geometric design over a range from 11 to 75. We demonstrate, thanks to a simple analytical model, that this coupling can be ascribed to a double FP cavity resonance, with the unique feature that each cavity is separately coupled to the outer medium.