研究目的
To demonstrate h-BN phononic crystal waveguides with designed pass and stop bands in the radio frequency (RF) range, and controllable wave propagation and transmission.
研究成果
The study successfully demonstrates the first phononic crystal waveguides in engineered h-BN nanomechanical structures, capable of supporting RF acoustic wave propagation over an effective length of 1.2 mm with a group velocity as high as 250 m/s at the first transmission band, while attenuating the transmission at the stop band and bandgap by over 40 dB. The phononic crystal design and methodology developed are directly transferable to other layered crystals beyond h-BN.
研究不足
The study is limited by the difficulty in obtaining h-BN flakes with very large uniform areas, which restricts the number of cells in the phononic crystal waveguides to around 20 for device fabrication.
1：Experimental Design and Method Selection:
The study employs arrays of coupled h-BN nanomechanical resonators with engineerable coupling strength to create phononic crystal waveguides.
2：Sample Selection and Data Sources:
The devices are fabricated using h-BN flakes transferred onto patterned SiO2/Si substrates.
3：List of Experimental Equipment and Materials:
A customized ultrasensitive laser interferometry system with an amplitude-modulated 405 nm blue laser as the driving beam and a continuous-wave 633 nm red laser as the detecting beam.
4：Experimental Procedures and Operational Workflow:
The mechanical motion of the suspended h-BN waveguide is photothermally actuated by the modulated 405 nm laser at one end, and the resultant phonon propagation is detected via a 633 nm laser interferometry system at the other end.
5：Data Analysis Methods:
The mechanical displacement of the device is transduced into the intensity variation of the reflected 633 nm laser beam and read out by a photodetector with frequency swept by a network analyzer.
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