Plasmonics: Enabling functionalities with novel materials

The Guest Editors sincerely thank all of the authors for their contributing articles. We are grateful to the Journal of Applied Physics Driving Editors, Professor Rachel Goldman and Professor David Aspnes, for their support as well as the American Institute of Physics publishing staff for helping and promoting the Special Topic issue “Plasmonics: Enabling functionalities with novel materials.” The Guest Editors also acknowledge the European Union’s Horizon 2020 Research and Innovation Program under Grant Agreement No. 899598 FET OPEN—PHEMTRONICS

Optically addressing interaction of Mg/MgO plasmonic systems with hydrogen

Magnesium-based films and nanostructures are being studied in order to improve hydrogen reversibility, storage capacity, and kinetics, because of their potential in the hydrogen economy. Some challenges with magnesium (Mg) samples are their unavoidable oxidation by air exposure and lack of direct in situ real time measurements of hydrogen interaction with Mg and MgO surfaces and Mg plasmonic nanoparticles. Given these challenges, the present article investigates direct interaction of Mg with hydrogen, as well as implications of its inevitable oxidation by real-time spectroscopic ellipsometry for exploiting the optical properties of Mg, MgH2 and MgO. The direct hydrogenation measurements have been performed in a reactor that combines a remote hydrogen plasma source with an in situ spectroscopic ellipsometer, which allows optical monitoring of the hydrogen interaction and results in optical property modification. The hydrogen plasma dual use is to provide the hydrogen-atoms and to reduce barriers to heterogeneous hydrogen reactions.European Commission under the H2020 grant TWINFUSYON (GA692034). Army Research Laboratory under Cooperative Agreement Number W911NF-17-2-0023. SODERCAN (Sociedad para el Desarrollo de Cantabria) through the Research Vicerrectorate of the University of Cantabria

Dynamic reflective color pixels based on molybdenum oxide

Active materials which show phase transitions, usually known as Phase Change Materials (PCM), have paved the way to a new generation of reconfigurable plasmonic platforms. Tunable color devices have experienced a great development in the recent years. In particular, reflective color filters can take advantage from sunlight to select and reflect a specific resonant wavelength in the visible spectrum range. Reflective displays are usually structural color filters based on asymmetric Fabry-Perot cavities (AFPCs). For a fixed geometry, most of AFPCs filters generate static color, limiting their potential as tunable color devices. Dynamic color is achieved by introducing an active layer whose optical properties can be modulated by an external stimuli. In this paper, we propose AFPCs based on molybdenum oxide (MoOx, 2<x<3) to achieve switchable on/off color reflective pixels. On and off states of the pixels are controlled through the stoichiometry of the MoOx layer.This work has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement (No 899598 – PHEMTRONICS)

Electromagnetic Study of Behaviour of Plasmonic Units

SUMMARY: For any memory or computing device, fast switching speed and low switching energy are most attractive attributes, and approaches by which speed and energy efficiency can be improved are always desirable. Plasmonics offers a way to achieve those attributes of fast switching and low energy consumption: plasmonic resonant structures are inherently capable of harnessing and focusing optical energy on sub-wavelength scales, far beyond the capabilities of conventional optical and photonic elements. Plasmonics can provide us with access to both of these scenarios. Indeed, plasmonics offers additional light manipulation tools, otherwise inaccessible with conventional photonics. The collective oscillation of conduction electrons in a suitably shaped metallic nanoparticle (the so-called localized surface plasmon, LSP) can couple with impinging radiation, which in turn squeezes light into much reduced volumes, and greatly magnifies the local electric field, usually leading to a much reduced (non-diffraction limited) device footprint. This deliverable presents an analysis of the electromagnetic interaction of plasmonic units with phase-change materials (PCMs) as selected in the project PHEMTRONICS. As plasmonic units, we start by considering the common plasmonic metals of gold and silver, analyzing their possibilities and limits. Based on those, we consider the use of metallic nanoantennas made of Ga nanoparticle dimers. Ga has been selected due to its good plasmonic performance, physical and chemical properties and to its polymorphism. We have analyzed the coupling of plasmonic nanoantennas with the PCMs under consideration at the moment in the project, namely, GaS and Sb2S3 in their amorphous and crystalline phases. These two PCMs have been combined with Ga NPs and some gold configurations to make the nanoantenna reconfigurabilty wider and improve its tunability and performance. Further, plasmon coupling to PCM waveguides made of Sb2S3, has been analyzed through metallic grating couplers. Two basic configurations have been selected which could be the base to design a plasmonic enhanced PCM photodetector in collaboration with the PHEMTRONICS partners. Finally, conclusions have been drawn together with the identification of the practical solutions to couple plasmonics with novel PCMs

Search for eccentric black hole coalescences during the third observing run of LIGO and Virgo

Despite the growing number of confident binary black hole coalescences observed through gravitational waves so far, the astrophysical origin of these binaries remains uncertain. Orbital eccentricity is one of the clearest tracers of binary formation channels. Identifying binary eccentricity, however, remains challenging due to the limited availability of gravitational waveforms that include effects of eccentricity. Here, we present observational results for a waveform-independent search sensitive to eccentric black hole coalescences, covering the third observing run (O3) of the LIGO and Virgo detectors. We identified no new high-significance candidates beyond those that were already identified with searches focusing on quasi-circular binaries. We determine the sensitivity of our search to high-mass (total mass M&gt;70 M⊙) binaries covering eccentricities up to 0.3 at 15 Hz orbital frequency, and use this to compare model predictions to search results. Assuming all detections are indeed quasi-circular, for our fiducial population model, we place an upper limit for the merger rate density of high-mass binaries with eccentricities 0&lt;e≤0.3 at 0.33 Gpc−3 yr−1 at 90\% confidence level

Ultralight vector dark matter search using data from the KAGRA O3GK run

Among the various candidates for dark matter (DM), ultralight vector DM can be probed by laser interferometric gravitational wave detectors through the measurement of oscillating length changes in the arm cavities. In this context, KAGRA has a unique feature due to differing compositions of its mirrors, enhancing the signal of vector DM in the length change in the auxiliary channels. Here we present the result of a search for U(1)B−L gauge boson DM using the KAGRA data from auxiliary length channels during the first joint observation run together with GEO600. By applying our search pipeline, which takes into account the stochastic nature of ultralight DM, upper bounds on the coupling strength between the U(1)B−L gauge boson and ordinary matter are obtained for a range of DM masses. While our constraints are less stringent than those derived from previous experiments, this study demonstrates the applicability of our method to the lower-mass vector DM search, which is made difficult in this measurement by the short observation time compared to the auto-correlation time scale of DM

Design of Switchable On/Off Subpixels for Primary Color Generation Based on Molybdenum Oxide Gratings

Structural color emerges from the interaction of light with structured matter when its dimension is comparable to the incident wavelength. The reflected color can be switched by controlling such interaction with materials whose properties can be changed through external stimuli such as electrical, optical, or thermal excitation. In this research, a molybdenum oxide (MoOx) reflective grating to get a switchable on/off subpixel is designed and analyzed. The design is based on subpixel on and off states that could be controlled through the oxidation degree of MoOx. A suitable combination of three of these subpixels, optimized to get a control of primary colors, red, green, and blue, can lead to a pixel which can cover a wide range of colors in the color space for reflective display applications.The authors received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No. 899598—PHEMTRONICS

Multiband, multi-polarization plasmonic photodetector and fabrication method

The present disclosure presents an innovative design concept for metal interdigitated grating-based metal-semiconductor-metal Schottky plasmonic photodetectors, able to detect multiband, multi-polarization electromagnetic radiation in the ultraviolet, visible, near and mid infrared spectrum by a using a single device with two electrodes which are both positioned on the same surface of semiconductor device, being thus a genuine planar semiconducting technology. The innovative concept shows that even if the surface plasmon enhanced photosensitive devices are wavelength and polarization-selective, it is possible to detect two and more narrow bands of the electromagnetic radiation with different polarizations by using a single-device two-electrode plasmonic Schottky photodetector where both metal contacts are placed on the device surface which is receiving the radiation. The novel design concept and associated fabrication technology will be presented by means of a generic metal-semiconductor-metal device, and specific examples will be then described.Solicitud Europea: 22465517.5 (17.03.2022)Nº Pub. Solicitud Europea: EP4246597A1 (20.09.2023

Quick and reliable colorimetric reflectometry forthe thickness determination of low-dimensionalQuick and reliable colorimetric reflectometry for the thickness determination of low-dimensional GaS and GaSe exfoliated layers by optical microscopy

Interest in gallium chalcogenides, i.e., gallium sulfide (GaS) and gallium selenide (GaSe), is growing rapidly due to its layered structure compatible with the fabrication of very thin layers by mechanical exfoliation and its wide band gap desirable for the design and fabrication of visible-UV optoelectronic devices. It is well known that the properties of these materials depend on their thickness; therefore, a facile and fast method is needed to infer the thickness of layered GaS and GaSe. Here, we report and validate a colorimetric method based on optical imaging for the quick and reliable quantitative determination of the thickness of exfoliated GaS and GaSe layers although it can be extended to other layered systems. For the validation of the method, the colorimetric computational estimate of the thickness is compared to the value obtained by atomic force microscopy. Further simulation of GaS and GaSe layers on different substrates of interest for different technological applications is provided as a quick guide for the rapid and reliable thickness determination of GaS and GaSe layers on various substrates.Funding. European Union’s Horizon 2020 research and innovation program (No 899598 – PHEMTRONICS)