Herein, a model is developed to study the polarization-selective light-coupling in quantum well infrared photodetector arrays with 15 and 30 μm pixel pitch. The polarization-selective light-coupling is achieved using 1D lamella gratings with varying grating orientation and studied through 2D and 3D finite-element method simulations. The extracted absorption quantum efficiency ηabs, derived from the field distribution, shows excellent agreement with experimental data in terms of absorption peak position for both pitch sizes. Several factors impacting the simulated absorptance level are discussed and a good agreement between the simulation and measured ηabs is achieved. Thanks to the developed 3D model, the polarization-selective light-coupling in pixels with 0° and 45° grating orientation is explored. The developed model paves the way for future studies on enhanced light-coupling in small pitch infrared detectors using resonance structures. © 2024 IRnova AB and The Author(s).

Computational efficiency is significantly enhanced using artificial neural network-based computing. A two-terminal memristive device is a powerful electronic device that can mimic the behavior of a biological synapse in addition to storing information and performing logic operations. This work focuses on the fabrication of a memristive device that utilizes a resistive switching layer composed of polyvinyl alcohol infused with ZnO nanoparticles. By incorporating ZnO nanoparticles into the polymer film, the fabricated memristive devices exhibit functionalities that closely resemble those of biological synapses, including short-term and long-term plasticity, paired-pulse facilitation, and spike time-dependent plasticity. These findings establish the ZnO nanoparticle-polymer nanocomposite as a highly promising material for future neuromorphic systems. © 2023 Author(s).

We integrated graphene with asymmetric metal metasurfaces and optimised the geometry dependent photoresponse towards optoelectronic molecular sensor devices. Through careful tuning and characterisation, combining finite-difference time-domain simulations, electron-beam lithography-based nanofabrication, and micro-Fourier transform infrared spectroscopy, we achieved precise control over the mid-infrared peak response wavelengths, transmittance, and reflectance. Our methods enabled simple, reproducible and targeted mid-infrared molecular sensing over a wide range of geometrical parameters. With ultimate minimization potential down to atomic thicknesses and a diverse range of complimentary nanomaterial combinations, we anticipate a high impact potential of these technologies for environmental monitoring, threat detection, and point of care diagnostics. © 2023 by the authors.

The production of materials that contain more than one functional constituent, the so-calledmultifunctional materials, is quite relevant in advanced technology. By acting as building blocks,nanoparticles can be suitably explored for generating higher-order multifunctional structures. In thisregard, herein, a special clustered magneto-fluorescent superstructure has been developed for nondestructivedetection of flaws and shallow subsurface discontinuities in industrial ferromagneticmaterials. The strategy consists of the solvophobic-controlled assembly of organic-based maghemitecores and water-based II–VI quantum dots, in the presence of hexadecyltrimethyl-ammonium bromide,CTAB, as a compatibilizer agent. This composite exhibited a high magnetic response (smax ¼ 66 emug1) and uniform size, in addition to tunable optical properties (QY ¼ 78%). The strategy of utilizingnanoparticles as magneto-fluorescent nanoprobes to identify tiny slits represents a great advance, forimproving the capability of precisely revealing the fracture boundary locations by visual real-timeinspection. The nanoscale probes exhibit a low signal-to-noise ratio and a higher competitiveperformance in relation to the existing micrometric detection systems. © The Royal Society of Chemistry 2021.

Infrared radiation reflection and transmission of a single layer of gold micropatch two-dimensional arrays, of patch length similar to 1.0 mu m and width similar to 0.2 mu m, have been carefully studied by a finite-difference time-domain (FDTD) method, and Fourier-transform infrared spectroscopy (FTIR). Through precision design of the micropatch array structure geometry, we achieve a significantly enhanced reflectance (85%), a substantial diffraction (10%), and a much reduced transmittance (5%) for an array of only 15% surface metal coverage. This results in an efficient far-field optical coupling with promising practical implications for efficient mid-infrared photodetectors. Most importantly we find that the propagating electromagnetic fields are transiently concentrated around the gold micropatch array in a time duration of tens of ns, providing us with a novel efficient near-field optical coupling. © 2021 by the authors.

Semiconductor nanowires have great potential for realizing broadband photodetectors monolithically integrated with silicon. However, the spectral range of such detectors has so far been limited to selected regions in the ultraviolet, visible and near-infrared. Here, we report on the first intersubband nanowire heterostructure array photodetectors exhibiting a spectrally resolved photoresponse from the visible to long-wavelength infrared. In particular, the infrared response from 3-20 mm is enabled by intersubband transitions in low-bandgap InAsP quantum discs synthesized axially within InP nanowires. The intriguing optical characteristics, including unexpected sensitivity to normal incident radiation, are explained by excitation of the longitudinal component of optical modes in the photonic crystal formed by the nanostructured portion of the detectors. Our results provide a generalizable insight into how broadband nanowire photodetectors may be designed, and how engineered nanowire heterostructures open up new fascinating opportunities for optoelectronics.

Quantum dots (QDs)-embedded photodiodes have demonstrated great potential on detectors. A modulation of QD charging opens intriguing possibilities for adaptive sensing with bias-tunable detector characteristics. Here, we report on a p-i-n GaAs photodiode with InAs QDs whose charging is tunable due to unintentional Be diffusion and trap-assisted tunneling of holes, from bias- and temperature (T)-dependent photocurrent spectroscopy. For the sub-bandgap spectra, the T-dependent relative intensities "QD-s/WL" and "WL/GaAs" (WL: wetting layer) reflect a dominant tunneling under -0.9 V (trap-assisted tunneling from the top QDs) and a dominant thermal escape under -0.2 ~ 0.5 V (from the bottom QDs since the top ones are charged and inactive for optical absorption) from QD s-state, a dominant tunneling from WL and an enhanced QD charging at > 190 K (related to trap level ionization). For the above-bandgap spectra, the degradation of the spectral profile (especially that near GaAs bandedge) as the bias and T tune (especially under -0.2 ~ 0.2 V and at > 190 K) can be well explained by the enhanced photoelectron capture in QDs with tunable charging; the dominant spectral profile with no degradation under 0.5 V is due to a saturated electron capture in charged QDs (i.e. charging neutralization). QD level simulation and schematic bandstructures help to understand these effects. © 2015 AIP Publishing LLC

Photocurrents (PCs) of three p–i–n GaAs solar cells, sample A with InAs quantum dots (QDs) embedded in the depletion region, B with QDs in the n region, and C without QDs, were studied experimentally and theoretically. Above GaAs bandgap, the PC of A is increased, while B is decreased with respect to C, since in A, the QD-induced reflection of hole wave function increases its overlap with electron wave function so that the optical transition rate is enhanced, while carrier mobility in B is reduced due to QD-induced potential variations. Moreover, A and B have increased PCs in the sub-GaAs-bandgap range due to QD optical absorptions.