The vibrational patterns of nanomechanical resonators are similar to different tones of a guitar chord and have similar properties such as frequency (pitch) and lifetime. Life is characterized by the quality factor, which is the number of times the resonator oscillates until its power is reduced by 70%. The quality factor is critical for modern applications of mechanical resonators because it determines the level of thermal noise, which is a limit for sensing weak forces and monitoring quantum effects.
Now, scientists at EPFL led by Professor Tobias J. Kippenberg have shown that a regular polygon suspended at its vertices supports vibration patterns along the circumference with very high quality factors. This is the result of the geometric symmetry of regular polygons, along with the elastic properties of structures under tension. This approach to loss engineering has an important advantage over previous techniques: achieving high quality factors in devices with much smaller footprints.
“The new surround modes not only beat the record for highest quality factor, but are about 20 times smaller than devices with similar performance,” says Nils Engelsen, senior author of the study. “Compactness brings real practical benefits. In our lab, we try to measure and control mechanical vibrations At the quantitative level using light, which requires suspension of mechanical resonators less than one micrometer from the structure directs the light. This feat is much simpler with the built-in hardware. “
The uncomplicated design of the polygon resonators allows the authors to take it one step further and create a series of connected polygon resonators. This series of paired oscillators can behave completely differently from a single resonator. The authors study the special dynamics of this chain, which arises from the method of connection of the resonators.
Precise force sensing is one of the important applications of nanomechanical resonators. By measuring the fluctuations of the position of the polygon resonator using optical interferometer, the authors show that these resonators can measure force fluctuations as low as 1 attonne. This level of sensitivity is close to the latest atomic force microscopes.
Says Mohamed Barihi, who led the study published in X . physical review.
“So far, improvements in mechanical quality factors have come at the expense of increased size and increased design complexity, which makes it very difficult to manufacture the latest devices. With ambient modes, it’s a different story. I think the simplicity of this new design greatly expands its potential for finding applications. new and promising.”
Muhammad J. Brihi et al., Surround patterns of nanomechanical resonators display quality factors exceeding 109 at room temperature, X . physical review (2022). DOI: 10.1103/ PhysRevX.12.021036