Optical read out and feedback cooling of a nanostring optomechanical cavity

Abstract

Optical measurement of the motion of a 940 kHz mechanical resonance of a silicon nitride nanostring resonator is demonstrated with a read out noise imprecision reaching 37 dB below that of the resonator's zero-point fluctuations. Via intensity modulation of the optical probe laser, radiation pressure feedback is used to cool and damp the mechanical mode from an initial room temperature occupancy of ${\bar{n}}_b=6.5\times 10^6$ ($T_b=295$K) down to a phonon occupation of $⟨n⟩=66\pm 10$, representing a mode temperature of $T_m\approx 3$mK. The five decades of cooling is enabled by the system's large single-photon cooperativity $(C_1=4)$ and high quantum efficiency of optical motion detection (${\eta }_t=0.27$).

13 pages, 13 figures

Cited by in corpus (1)

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