RESUMO
Multilayer (ML) thin films are an optical engineering strategy to address reflectivity losses in GaAs photovoltaic devices, enhancing the power conversion of light around a single wavelength. Inspired by the enhanced response of periodic ML Bragg mirrors, the authors introduce quite simple antireflective designs based on two periods and single periods of A l 2 O 3/S i O 2 bilayer stacks. The reflectivity losses of the systems are evaluated with the aid of numerical simulations, and their dimensions are optimized to enhance the transmission of plane waves towards GaAs substrates. Reflectivity losses are evaluated at angles off the normal for s- and p-polarized light, exhibiting gains at broader angles and the quenching of undesired s-t o-p optical anisotropy, inherent to GaAs substrates. ML stacks were fabricated by RF sputtering deposition on G a A s-n and p+ type substrates and characterized by UV-Vis spectroscopy techniques to evaluate the role of carriers on coating performance.
RESUMO
In this letter, the authors develop an optimized Seebeck nanoantenna design suitable for IR harvesting applications. The design is optimized via the so-called particle-swarm-optimization algorithm (PSO), an evolutionary algorithm able to drive the morphology of a nano-object towards an optimum. Along with the so-called nanoloading technique, efforts are subsequently addressed to understand the physical mechanisms behind the wave energy to voltage conversion, from both numerical and theoretical perspectives. In particular, the thermal and intrinsic impedance are considered to be the key issues beneath the device's response.
RESUMO
The multi-resonant response of three-steps tapered dipole nano-antennas, coupled to a resistive and fast micro-bolometer, is investigated for the efficient sensing in the infrared band. The proposed devices are designed to operate at 10.6 µm, regime where the complex refractive index of metals becomes important, in contrast to the visible counterpart, and where a full parametric analysis is performed. By using a particle swarm algorithm (PSO) the geometry was adjusted to match the impedance between the nanoantenna and the micro-bolometer, reducing the return losses by a factor of 650%. This technique is compared to standards matching techniques based on transmission lines, showing better accuracy. Tapered dipoles therefore open the route towards an efficient energy transfer between load elements and resonant nanoantennas.
RESUMO
Arrays of metallic thermocouples in the shape of spiral nanoantennas are proposed as infrared detectors, which use the thermoelectric properties of the metallic interfaces to generate electrical DC signals. The responsivity of these types of antennas is evaluated from both theoretical and numerical perspectives pointing out its potential as infrared sensors. Moreover, the same structures can be used to characterize the state of polarization of the optical near fields with a spatial resolution comparable to the wavelength.