Berlin 2018 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 97: Scanning probe techniques: Method development II

O 97.5: Vortrag

Donnerstag, 15. März 2018, 16:00–16:15, MA 005

Intermodulation gain and noise squeezing in dynamic AFM — •David Haviland, Alexander Revera-Ahlin, Daniel Forchheimer, Riccardo Borgani, Thomas Weissl, and Shan Jolin — Nanostructure Physics, KTH, Stockholm, Sweden

When driven by a strong pump, a nonlinear oscillator will create correlations in the frequency domain between signal and idler pairs symmetrically placed about the pump frequency. These correlations result in two-mode squeezing, giving power gain to a weak signal by amplifying one quadrature while the other quadrature is de-amplified. Not only signals but also noise can be squeezed, resulting in measurement sensitivity below the standard limits imposed by thermal or quantum fluctuations. There is currently numerous experiments demonstrating these effects at the quantum limit, but much less attention has been paid to the squeezing of thermal noise where there is in fact great potential for practical applications. We demonstrate parametric gain and thermal noise squeezing in a room-temperature dynamic Atomic Force Microscopy, where the limiting noise is thermal Brownian motion of the cantilever. Unlike previous work on the mechanical amplification of force, we do not use an 'external' nonlinearity to realize gain, but rather the sample itself is used as the 'gain medium'. We show how parametric gain results in a widening of the measurement bandwidth over which dynamic AFM is limited by thermal noise.