Abstract
We demonstrate how noise can be turned into an advantage for optical sensing using a nonlinear cavity. The cavity is driven by a continuous wave laser into the regime of optical bistability. Due to the influence of fluctuations, the cavity randomly switches between two states. By analyzing residence times in these two states, perturbations to the resonance frequency of the cavity can be detected. Here, such an analysis is presented as a function of the strength of the perturbation and of the noise. By increasing the standard deviation of the noise, we find that the detection speed increases monotonically while the sensitivity peaks at a finite value of the noise strength. Furthermore, we discuss how noise-assisted sensing can be optimized in state-of-the-art experimental platforms, relying solely on the minimum amount of noise present in the cavity due to its dissipation. These results open new perspectives for the ultrafast detection of nanoparticles, contaminants, gases, or other perturbations to the resonance frequency of an optical resonator, at low powers and in noisy environments.
Highlights
A sensor is a device that reports a change in its environment
In 2002, Gammaitoni and Bulsara introduced a sensor the performance of which can be enhanced by nonlinearity and noise; they called it a noise-activated nonlinear dynamical sensor (NANDS) [2]
The physics of a NANDS is reminiscent of the Brownian particle in a double-well potential (DWP) mastered by Kramers [3]
Summary
A sensor is a device that reports a change in its environment. The sensor-environment coupling leads to dissipation, which—according to the fluctuationdissipation theorem [1]—makes the output of the sensor necessarily noisy. Experiments and calculations on NANDS have focused on configurations involving a periodic modulation of the DWP [5,6,7,8,9,10], where noise plays a secondary role with respect to the periodic force This is likely the best detection strategy in systems where slow dynamics and weak noise make fully noise-activated sensing too slow or impractical. As long as those sensors remain linear, time-invariant, and passive, noise stands on the way of exploiting the enhanced sensitivity to detect small perturbations [24,25,26] These developments suggest that a detection strategy that harnesses rather than avoids noise, as in the RTD scheme, may lead to a new frontier in optical sensing. We show that optically bistable resonators can be used as sensors with the following remarkable properties: (i) a detection speed that increases monotonically with the standard deviation of the noise and (ii) a sensitivity that is maximized for a particular value of the standard deviation of the noise
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