Sensors & Transducers



Vol. 258, Issue 4, July 2022, pp. 1-9





1,2 Timo SOMMER, 1,2,3 David HOCH, 1 Kevin-Jeremy HAAS,
1 Leopold MOLLER, 1 Julius RÖWE, 1 Aditya YADAV, 1,4 Pedro SOUBELET,
1,2,4 Jonathan J. FINLEY and 1,2,3,* Menno POOT



1 Department of Physics, Technical University of Munich, 85748 Garching, Germany

2 Munich Center for Quantum Science and Technology (MCQST), 80799 Munich, Germany

3 Institute for Advanced Study, Technical University of Munich, 85748 Garching, Germany

4 Walter Schottky Institute, Technical University of Munich, 85748 Garching, Germany

1 Tel.: +49 89 289 12358, fax: +49 89 289 12536

E-mail: menno.poot@tum.de



Received: 2 June 2022 /Accepted: 5 July 2022 /Published: 29 July 2022





Abstract: Visualizing eigenmodes is crucial for understanding the dynamics of state-of-the-art micromechanical devices. A method is established to map modes of mechanical structures optically. This fast and robust method, based on parallel modified phase-lock loops outperformed three alternative approaches. The setup used is discussed here in more detail, and the modal decomposition results are investigated further, including a study of the orthogonality of the eigenmodes and the mixing of degenerate modes. Crosstalk, however, remained a problem, especially for membranes with a small mechanical response. The issue is investigated using numerical simulations of the phase-lock loop operation, which indicate that without crosstalk compensation, the mode maps will be strongly distorted. To solve this, the phase-lock loop is equipped with crosstalk compensation and it is shown that now also in the presence of strong crosstalk, where resonances and phase responses are distorted, accurate maps are obtained.


Keywords: Optomechanics, Mode-mapping, MEMS, Phase-lock loop, Silicon-nitride, Membrane, Crosstalk.

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