Stuttgart 2012 – wissenschaftliches Programm
Q 16.9: Vortrag
Montag, 12. März 2012, 18:30–18:45, V7.03
A hybrid on-chip optonanomechanical transducer for ultra-sensitive force measurements — •Emanuel Gavartin1, Pierre Verlot1, and Tobias J. Kippenberg1,2 — 1Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland — 2Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Straße 1, 85748 Garching
Nanomechanical oscillators have been employed as transducers to measure force, mass and charge with high sensitivity. They are also used in opto- or electromechanical experiments with the goal of quantum control and phenomena of mechanical systems. Here, we report the realization and operation of a hybrid monolithically integrated transducer system consisting of a high-Q nanomechanical oscillator with modes in the MHz regime coupled to the near-field of a high-Q optical whispering-gallery-mode microresonator. The transducer system enables a sensitive resolution of the nanomechanical beam’s thermal motion with a signal-to-noise of five orders of magnitude and has a force sensitivity of 74 aN Hz−1/2 at room temperature. Energy averaging, required to retrieve incoherent signals, converges only very slowly with the fourth root of the averaging time. We propose and explicitly demonstrate by detecting a weak incoherent force that this constraint can be significantly relaxed by use of dissipative feedback. We achieve a more than 30-fold reduction in averaging time with our hybrid transducer and are able to detect an incoherent force having a force spectral density as small as 15 aN Hz−1/2 within 35 s of averaging. This corresponds to a signal which is 25 times smaller than the thermal noise and would otherwise remain out of reach.