arXiv subjects

Alex G. Krause

Publications and source records attributed to Alex G. Krause.

2 recordsLinked to original sources

arXiv2015

Optical read out and feedback cooling of a nanostring optomechanical cavity

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 $\langle n \rangle = 66 \pm 10$, 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 ($η_{t} = 0.27$).

physics.optics↗

arXiv2015

Nonlinear radiation pressure dynamics in an optomechanical crystal

Utilizing a silicon nanobeam optomechanical crystal, we investigate the attractor diagram arising from the radiation pressure interaction between a localized optical cavity at $λ= 1552$nm and a mechanical resonance at $ω/2π= 3.72$GHz. At a temperature of $T \approx 10$K, highly nonlinear driving of mechanical motion is observed via continuous wave optical pumping. Introduction of a time-dependent (modulated) optical pump is used to steer the system towards an otherwise inaccessible dynamically stable attractor in which mechanical self-oscillation occurs for an optical pump red-detuned from the cavity resonance. An analytical model incorporating thermo-optic effects due to optical absorption heating is developed, and found to accurately predict the measured device behavior.

physics.optics↗