Analysis of Sound Absorption Characteristics of Acoustic Ducts with Periodic Additional Multi-Local Resonant Cavities

With the aim of applying various Helmholtz resonant cavities to achieve low-frequency sound absorption structures, a pipe structure with periodic, additional, symmetrical, multi-local resonant cavities is proposed. A thin plate with additional mass is placed in the cylindrical Helmholtz resonant cavity structure to form a symmetric resonant cavity structure and achieve multi-local resonance. The simulation results show that the periodic structure proposed in this paper can produce multiple, high acoustic transmission loss peaks and multiple lower broadband sound absorption frequency bands in the low-frequency range. In this paper, this idea is also extended to the Helmholtz resonant cavity embedded with multiple additional mass plates. The results show that the periodic arrangement of the multi-local resonant symmetric cavity inserted into multiple plates with mass can significantly increase its transmission loss and show a better performance on low-frequency sound absorption characteristics.

First results of the CAST-RADES haloscope search for axions at 34.67 μeV

We present results of the Relic Axion Dark-Matter Exploratory Setup (RADES), a detector which is part of the CERN Axion Solar Telescope (CAST), searching for axion dark matter in the 34.67 μeV mass range. A radio frequency cavity consisting of 5 sub-cavities coupled by inductive irises took physics data inside the CAST dipole magnet for the first time using this filter-like haloscope geometry. An exclusion limit with a 95% credibility level on the axion-photon coupling constant of gaγ ≳ 4 × 10−13 GeV−1 over a mass range of 34.6738 μeV < ma< 34.6771 μeV is set. This constitutes a significant improvement over the current strongest limit set by CAST at this mass and is at the same time one of the most sensitive direct searches for an axion dark matter candidate above the mass of 25 μeV. The results also demonstrate the feasibility of exploring a wider mass range around the value probed by CAST-RADES in this work using similar coherent resonant cavities.

Effect of device structure on signal measurement of zinc oxide nanocolumn-based resonant cavity hydrophones

Hydrophones with three different resonant cavities (microscope slide, cavity with 9.8 mm diameter and 5.7 mm[Formula: see text] curve surface, and cavity with 14 mm diameter and 6.5 mm[Formula: see text] curve surface) and with two different electrode structures (interdigital electrode, without the interdigital electrode but with top–bottom structure) were designed and fabricated. Zinc oxide (ZnO) film was deposited on indium–tin oxide/glass as seed layer and ZnO nanocolumns were grown as the piezoelectric material. Grown ZnO nanocolumns were used in all samples as the sound receiver of all designed hydrophones to enhance the sensing effect and efficiency of fabricated hydrophones. The electrode mask was then adhered on the surfaces of ZnO nanocolumns to complete the electrodes of designed resonant cavity. While measuring the hydrophones without interdigitated electrode, the measurement probes were contacted directly on the substrate and on the top layer of the material. Finally, the resonant cavities in all designed hydrophones were encapsulated using epoxy resin to finish the package of the fabricated hydrophones, and then the sound receiving performance of the hydrophones was evaluated in the water and the results were well compared in this study.

Design of Broadband Infrared Photodetectors Enhanced by Dual-Mode Plasmonic Resonant Cavities

The signal-to-noise ratio of infrared photodetectors can be improved by using resonant cavities, whereas the enhancement effect usually occurs in a narrow wavelength range. Here, we propose a dual-mode plasmonic resonant cavity which can enhance the performance of infrared photodetectors in a wide range of wavelengths from 3.5 μm to 5.5 μm. The optical cavity consists of an Au grating, an ultrathin (310 nm) detective layer of mercury cadmium telluride, and an Au film, which can exhibit nearly perfect absorption at resonant wavelengths with using optimal parameters. For the target wavelength range, the wavelength-averaged absorption in the detective layer can also be 62%, about 12 times of that without the resonant cavity. Such a high enhancement of absorption can occur for incident light in a broad range of angle (θ < 45⁰) and with different polarizations.