Multimode laser cooling and ultra-high sensitivity force sensing with nanowires

TL;DR

This paper demonstrates broadband multimode laser cooling of nanowires to 8 K and enhances force sensing sensitivity to sub-zeptonewton levels using active feedback, improving measurement performance for various applications.

Contribution

It introduces a novel multimode cooling technique and active feedback methods that significantly improve force sensing sensitivity and measurement speed in nanowire-based sensors.

Findings

Achieved -23 dB cooling to 8 K in nanowires.

Reached force sensitivity below 2×10⁻¹⁶ N at room temperature.

Showed that feedback and post-processing yield similar improvements.

Abstract

Photo-induced forces can be used to manipulate and cool the mechanical motion of oscillators. When the oscillator is used as a force sensor, such as in atomic force microscopy, active feedback is an enticing route to enhancing measurement performance. Here, we show broadband multimode cooling of $-23$ dB down to a temperature of $8 \pm 1$~K in the stationary regime. Through the use of periodic quiescence feedback cooling, we show improved signal-to-noise ratios for the measurement of transient signals. We compare the performance of real feedback to numerical post-processing of data and show that both methods produce similar improvements to the signal-to-noise ratio of force measurements. We achieved a room temperature force measurement sensitivity of $< 2\times10^{-16}$ N with integration time of less than $0.1$ ms. The high precision and fast force microscopy results presented will potentially benefit applications in biosensing, molecular metrology, subsurface imaging and accelerometry.