ORCID Profile
0000-0003-4811-5774
Current Organisation
Hong Kong University of Science and Technology
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Publisher: AIP Publishing
Date: 15-03-2021
DOI: 10.1063/5.0040244
Abstract: In this paper, we report on the observation of nonlinear effects in a nanostrip phononic metasurface (NPM) that enable the tuning of resonance frequencies at 1.42 GHz. The NPM resonator made of a periodic nanostrip array is fabricated on a lithium niobate substrate. Each of the nanostrips is 250 nm wide and is made of a 680-nm-thick SiO2 layer stacking on 50-nm Al metal electrodes. Finite element analysis reveals that the device operates in a vertically polarized (compression) mode with substantial acoustic energy confined in the nanostrips, leading to a local resonance at low acoustic velocity. Due to the nonlinearity, the resonance frequency of the device decreases with the increase in stimulation power. The underlying mechanism of the nonlinearity is found to be the power-dependent coupling of the adjacent nanostrips. This coupling induces softening of the substrate surface region, which reduces the acoustic velocity and, hence, the bulk radiation. As a result, the quality factor of the NPM resonator is found to improve with the increase in stimulation power. The power-dependent coupling of nanostrips in the NPM resonator demonstrates a reliable method for the realization of nonlinearity in phononic metasurfaces, which would significantly enrich the mechanisms for the manipulation of surface acoustic waves at high frequencies.
Publisher: Springer Science and Business Media LLC
Date: 18-01-2021
DOI: 10.1038/S41378-020-00236-9
Abstract: Acoustic wave resonators are promising candidates for gravimetric biosensing. However, they generally suffer from strong acoustic radiation in liquid, which limits their quality factor and increases their frequency noise. This article presents an acoustic radiation-free gravimetric biosensor based on a locally resonant surface phononic crystal (SPC) consisting of periodic high aspect ratio electrodes to address the above issue. The acoustic wave generated in the SPC is slower than the sound wave in water, hence it prevents acoustic propagation in the fluid and results in energy confinement near the electrode surface. This energy confinement results in a significant quality factor improvement and reduces frequency noise. The proposed SPC resonator is numerically studied by finite element analysis and experimentally implemented by an electroplating-based fabrication process. Experimental results show that the SPC resonator exhibits an in-liquid quality factor 15 times higher than a conventional Rayleigh wave resonator at a similar operating frequency. The proposed radiation suppression method using SPC can also be applied in other types of acoustic wave resonators. Thus, this method can serve as a general technique for boosting the in-liquid quality factor and sensing performance of many acoustic biosensors.
Publisher: Elsevier BV
Date: 2019
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2021
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2018
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 02-2021
Publisher: Wiley
Date: 17-01-2023
Abstract: Phononic crystals (PnCs) exhibit acoustic properties that are not usually found in natural materials, which leads to the possibility of new devices for the complex manipulation of acoustic waves. In this article, a micron‐scale phononic waveguide constructed by line defects in PnCs to achieve on‐chip, tightly confined guiding, bending, and splitting of surface acoustic waves (SAWs) is reported. The PnC is made of a square lattice of periodic nickel pillars on a piezoelectric substrate. The PnC lattice constant, pillar diameter, and pillar height are set to 10, 7.5, and 3.2 µm, respectively, leading to a complete bandgap centered at 195 MHz. Interdigitated transducers are monolithically integrated on the same substrate for SAW excitation. The guiding, bending, and splitting of SAWs in the phononic waveguide are experimentally observed through measurement of the out‐of‐plane displacement fields using a scanning optical interferometer. The combination of destructive interference due to the Bragg bandgap and the interaction of the propagating wave with the pillars around the channel results in a tight confinement of the displacement field. The proposed phononic waveguides demonstrate the feasibility of precise local manipulation of SAW that is essential for emerging frontier applications, notably for phonon‐based classical and quantum information processing.
No related grants have been discovered for Feng Gao.