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Far infrared spectrometers have a prominent role to play in future space missions devoted to unveiling the obscure universe. Diffraction gratings are the heart of these instruments that, when operating in the range of a few terahertz, shall cover a wide spectral range providing the highest resolution and efficiency, generally for only a single polarization, within the specified spectral range. This contribution describes the optimization of the diffraction efficiency of the first diffractive order for a blazed metallic grating working at a large angle of incidence. Since the grating period is of the same order of magnitude as the wavelength, it is necessary to approach the design by solving Maxwell's equations rigorously using computational electromagnetism. We have applied the rigorous coupled-wave analysis and the finite element methods to simulate the performance of the grating. This analysis provides relevant hints for the selection of the period, and the blaze and slant angles of the grating. A metallic blazed grating has been fabricated on aluminum and its topography has been characterized to determine the discrepancies with respect to the nominal values. The fabricated profile has been simulated to obtain the expected results in efficiency in comparison with the ideal case. This analysis provides guidance for improved manufacturing processes and experimental verification.

We study the light emission of plasmonic-luminescent hybrid nanostructures consisting of Ag nanoparticles (NPs) embedded in europium oxide (EuOX). The Ag NPs present a bidimensional organization in the nanostructures and they optically behave as oblate spheroids. The photoluminescence (PL) spectral response of the nanostructures evolves from a narrow red emission characteristic of Eu3+ions in absence of Ag NPs to a broad blue-green emission band associated with Eu2+ions when the layer of Ag NPs is present. This behavior is not related to a change in the Eu2+/Eu3+ratio, which is verified by compositional analysis. Instead, a detailed investigation of the PL emission of the nanostructures suggests that the coupling of the Ag NPs to the Eu2+ions present in the EuOXlayer, which manifests itself in an efficient sensitization of these ions, enhances their broad visible emission. In particular, the longitudinal mode of the Ag NPs surface plasmon is considered to be responsible for the efficient energy transfer for the non-normal incidence excitation PL configuration used. Finally, the use of a capping amorphous Al2O3layer allows improving the robustness of hybrid nanostructures and further enhances their PL emission. These findings provide a new path to actively control the selective excitation of Eu2+and Eu3+ions via a controlled coupling with the surface plasmon resonance modes of the Ag NPs and points to these nanostructures as promising building blocks for the development of integrable white light sources.

We present in this work a numerical model for characterizing the scattering properties of the human lens. After analyzing the scattering properties of two main scattering particles actually described in the literature through FEM (finite element method) simulations, we have modified a Monte Carlo’s bulk scattering algorithm for computing ray scattering in non-sequential ray tracing. We have implemented this ray scattering algorithm in a layered model of the human lens in order to calculate the scattering properties of the whole lens. We have tested our algorithm by simulating the classic experiment carried out by Van der Berg et al for measuring “in vitro” the angular distribution of forward scattered light by the human lens. The results show the ability of our model to simulate accurately the scattering properties of the human lens.

Electrically biased metal nanostructures are at the core of innovative multifunctional integrated devices that control the flow of electrons and photons at the nanoscale. They are based on plasmonic structures that create strongly confined fields, typically associated with large temperature gradients. These thermal effects may generate artifact responses detrimental to the desired operation. We show here how a biasing polarity and a local optical excitation asymmetry of a generic geometry – a nanoscale constriction – interplay thermally to modify the diffusive electron transport in out-of-equilibrium conditions. Our experimental results are accompanied with computational electromagnetism and multiphysics simulations.

A structure based on a dimer of silicon nanoparticles, presenting directional scattering in the visible range, was studied as a new design of an all-optical switch. The combination of spherical nanoparticles satisfying, at the same incident wavelength, the zero-backward and the minimum-forward scattering conditions can produce either a maximum or a minimum of the scattered field in the area between the nanoparticles. The modulation of the incident wavelength can be used as a switching parameter due to the sensitivity of these conditions to it. An optimization of the dimer setup, both in the distance between the nanoparticles and the incident wavelength, was numerically performed to obtain a maximum contrast. Also, near-field and far-field distributions of the electric field have been considered.

Directional steerability can be obtained for an array of optical antennas through selective heating of the individual elements. Heating changes electrical conductivity of the heated element, which affects the phase of the generated currents. The variation in temperature can be obtained by modifying the biasing point of the individual elements of the array, which would allow fast reconfiguration. The numerical evaluation of the performance of an array of a reduced number of antennas (2 and 3) shows the feasibility of this approach.

This Letter shows the effect of the geometrical and material properties of lead lines and connections on the robustness and reliability of optical antennas working as distributed bolometers. We analyze the operational limits of the biasing voltage using a mutiphysics finite element method. We demonstrate that, after evaluating the effect of the electromagnetic irradiance falling on the device, biasing voltage is the main limiting factor to maintain operative titanium optical antennas. Results have been experimentally verified by finding the biasing values needed to destroy optical antennas working as distributed bolometers. Structural damage has been identified from scanning electron microscopy images.