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Schematical transduction setup; the electronic path is plotted in black; the area surrounded by the dashed rectangle depicts the optical path; arrows indicate the direction of signal propagation. The sample containing a string as nanomechanical resonator is mounted in vacuum just below the end of the optical fiber as indicated. As the sample is actuated at and the illuminating laser intensity is modulated at a coherent, low-frequency beat at is created on the photodetector.
(a) Mechanical response and Lorentzian fit of a nanomechanical stretched SiN wire with dimensions length, width, and height, respectively, driven around the second harmonic mode. (b) Resonance frequencies and quality factors of the fundamental mode and all observed harmonics are plotted vs mode number , reflecting the number of antinodes along the length of the wire. To emphasize the scaling behavior of the frequencies a linear fit is shown. (c) Spatial distribution of the phase of the observed mechanical modes as measured with the detection fiber moved by position along the wire (see Fig. 1). For clarity the curves are offset in phase with respect to each other.
(a) Nonlinear response of the fifth harmonic mode; experimental data (black) and theoretical fit (red). The fit is employed to convert the detected signal into mechanical displacement. [(b) and (c)] Comparison of signal transduction using stroboscope (a) and (b) and cw illumination (c) measuring with 50 Hz bandwidth. Note that the driving amplitude in (a) and (c) are identical; therefore the noise floor in (c) can be estimated to be about 2 nm and is substantially larger than the one of about 50 pm (b) achieved in the stroboscopic detection scheme.
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