Acoustic filters and metamaterials have become essential components for elastic wave control in applications ranging from ultrasonics to noise abatement. Other devices have been designed in this field, emulating their electromagnetic counterparts. One such case is an acoustic diode or rectifier, which enables one-way wave transmission by breaking the wave equation-related reciprocity. Its achievement, however, has proved to be rather problematic, and current realizations display a number of shortcomings in terms of simplicity and versatility. Here, we present the design, fabrication and characterization of a device able to work as an acoustic diode, a switch and a transistor-like apparatus, exploiting symmetry-breaking nonlinear effects like harmonic generation and wave mixing, and the filtering capabilities of metamaterials. This device presents several advantages compared with previous acoustic diode realizations, including versatility, time invariance, frequency preserving characteristics and switchability. We numerically evaluate its efficiency and demonstrate its feasibility in a preliminary experimental realization. This work may provide new opportunities for the practical realization of structural components with one-way wave propagation properties.
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http://dx.doi.org/10.1038/s41598-019-44843-7 | DOI Listing |
Food Chem
February 2025
Department of Analytical Chemistry, Faculty of Sciences, Institute for Viticulture and Agrifood Research (IVAGRO), University of Cadiz, Agrifood Campus of International Excellence (ceiA3), 11510 Puerto Real, Cadiz, Spain.
Bioactive compounds in food offer health benefits by influencing cellular and physiological functions. Tryptophan, an essential amino acid and precursor to neurotransmitters like melatonin and serotonin, regulates mood and circadian rhythms. However, its quantification in mushrooms is scarce studied.
View Article and Find Full Text PDFSci Rep
October 2024
Photonics Research Group, Ghent University-IMEC, Technologiepark-Zwijnaarde 126, 9052, Ghent, Belgium.
Photoacoustic imaging has emerged as a powerful, non-invasive modality for various biomedical applications. Conventional photoacoustic systems require contact-based ultrasound detection and expensive, bulky high-power lasers for the excitation. The use of contact-based detectors involves the risk of contamination, which is undesirable for most biomedical applications.
View Article and Find Full Text PDFMicromachines (Basel)
August 2024
Department of Electrical and Computer Engineering, Texas A&M University, College Station, TX 77843, USA.
This article reports the fine-tuning of the optical resonance wavelength (ORW) of surface-micromachined optical ultrasound transducer (SMOUT) arrays to enable ultrasound data readout with non-tunable interrogation light sources for photoacoustic computed tomography (PACT). Permanent ORW tuning is achieved by material deposition onto or subtraction from the top diaphragm of each element with sub-nanometer resolution. For demonstration, a SMOUT array is first fabricated, and its ORW is tuned for readout with an 808 nm laser diode (LD).
View Article and Find Full Text PDFNature
October 2024
Department of Electrical and Computer Engineering, Cornell University, Ithaca, NY, USA.
Unlike non-polar semiconductors such as silicon, the broken inversion symmetry of the wide-bandgap semiconductor gallium nitride (GaN) leads to a large electronic polarization along a unique crystal axis. This makes the two surfaces of the semiconductor wafer perpendicular to the polar axis substantially different in their physical and chemical properties. In the past three decades, the cation (gallium) face of GaN has been used for photonic devices such as light-emitting diodes (LEDs) and lasers.
View Article and Find Full Text PDFRev Sci Instrum
August 2024
Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia 26506, USA.
The small signal-to-noise ratio (SNR) of conventional laser induced fluorescence (LIF) measurements using a continuous wave laser, either diode or dye, is typically overcome by amplitude modulating the laser at a specific frequency and then using lock-in amplification to extract the signal from measurement noise. Here, we present LIF measurements of the neutral helium velocity distribution function in an rf plasma using frequency modulated (FM) laser injection. A pulse train of 100% amplitude modulation is generated synthetically with a random sequence of pulse lengths.
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