Optical solar reflector smart radiators are able to control the temperature of spacecraft. This work demonstrates a novel smart optical solar reflector using a patterned thermo-chromic VO2 plasmonic meta-surface design. The VO2 meta-surface combines the temperature induced phase transition of VO2 with plasmonic resonances resulting in a significant enhancement of the infrared absorption. The enhanced absorption obtained at a reduced VO2 coverage results in superior emittance tunability Δε and lower solar absorptance α compared to a corresponding thin-film reflector. An emittance tunability of 0.48 is obtained for the meta-reflector design, representing a 30% improvement compared to the unstructured film. Meta-surface based smart optical solar reflectors offer a new route toward energyefficient and cost-effective passive thermal control systems of spacecraft and other surfaces.

Optical Solar Reflectors are devices that combine high reflection for visible wavelengths with a strong emissivity in the infrared. Compared to the conventional rigid quartz tiles used on spacecraft since the 1960s, thin-film solutions can offer a significant advantage in weight, assembly and launch costs. Here, we present a metasurface based approach using an Al-doped * To whom correspondence should be addressed † Electronics ‡ Physics ¶ CREO § NILT ZnO (AZO) transparent conducting oxide as infrared plasmonic material. The AZO is patterned into a metasurface to achieve broad plasmonic resonances with enhanced absorption of electromagnetic radiation in the thermal infrared. In the visible range, the transparent conducting oxide provides low losses for solar radiation, while intrinsic absorption losses in the ultraviolet range are effectively suppressed using a multilayer reflecting coating. The addition of high-emissivity layers to the stack eventually results in comparable emissivity values to the thin plasmonic device, thus defining a window of opportunity for plasmonic absorption as a design strategy for ultrathin devices. The optimized experimental structure achieves solar absorptance (α) of 0.16 and thermal emissivity (ε) of 0.79. Our first prototype demonstrator paves the way for further improvement and large-area fabrication of metasurface solar reflectors, and ultimately their application in space missions.

The optical properties of Mg(I) have been computed using a configuration-interaction (CI) approach in which the multielectron basis includes single and double excitations from the M shell plus single excitations from the Ne-like core. The orbital set is of L 2 type and comprises STO, hydrogenic plus spatial oscillating STOCOS functions. The continuum states have been obtained by solving a discretized integral equation for the K matrix half-on-the-energy shell. For the 1 S e , 1 P e , 1 P 0 and 1 D e manifolds we have computed the discrete and autoionizing levels of the 3snl, 3pnl, 4snl and 3dnl series, the last two lying beyond the 3p ionization threshold.

Smart radiative cooling devices based on thermochromic materials such as vanadium dioxide (VO2) are of practical interest for temperature regulation and artificial homeostasis, i.e., maintaining stable equilibrium conditions for survival, both in terrestrial and space applications. In traditional solar reflector configurations, solar absorption in the VO2 layer is a performance limiting factor due to the multiple reflections of sunlight in the stack. Here, we demonstrate a visually transparent, smart radiator panel with reduced solar absorption. An Al-doped ZnO transparent conducting oxide layer acts as a frequency selective infrared back-reflector with high transmission of solar radiation. In this study we make use of high-quality VO2 thin films deposited using atomic layer deposition and optimized annealing process. Patterning of the VO2 layer into a metasurface results in a further reduction of the solar absorption parameter α to around 0.3, while exhibiting a thermal emissivity contrast Δε of 0.26 by exploiting plasmonic enhancement effects. The VO2 metasurface provides a visual spectrum transmission of up to 62%, which is of interest for a range of applications requiring visual transparency. The transparent smart metasurface thermal emitter offers a new approach for thermal management in both space and terrestrial radiative cooling scenarios.

A compact portable and standalone point sensor has been developed for the detection and identification of precursors of improvised explosive devices (IEDs) and to be part of a network of sensors for the discovery of hidden bomb factories in homeland security applications. The sensor is based on quartz enhanced photoacoustic spectroscopy (QEPAS), and it implements a broadly tunable external cavity quantum cascade laser source (EC-QCL). It makes use of an optical cell purposely designed with a miniaturized internal volume, to achieve fast response and high sensitivity, and that can also be heated to improve sensitivity towards less volatile compounds. The sensor has been assembled and successfully tested in the lab with several compounds, including IED's precursors such as acetone, nitromethane, nitric acid, and hydrogen peroxide. The identification capability and limits of detection near the ppm level have been estimated for all these compounds.