Noise is normally the bane of electronic sensors. While biological organisms can make great use of noise, man-made electronics go to great lengths to reduce signal noise as much as possible.
Now, Penn State researchers have found that a small amount of background noise can enhance the performance of light sensors when the light is too dim to sense otherwise.
The sensor is based on a two-dimensional material called molybdenum disulfide, an inorganic compound used in many high-end sensors. While the sensor used in the study detected light, it could also be used for many other types of sensors as it requires low amounts of energy.
Stochastic resonance (SR) is a phenomenon where a signal that is normally too weak to be detected by a sensor, can be boosted by adding white noise to the signal, which contains a wide spectrum of frequencies.
The key to the technology is a phenomenon called stochastic resonance, where a signal too weak to be detected is boosted by adding white noise on a wide spectrum of frequencies. It’s one of those astounding phenomena, where noise, which is considered detrimental for electronic circuits and communication systems, actually ends up playing a constructive role in the detection of weak signals.
The inspiration for the study came from nature, says lead author Saptarshi Das, an assistant professor of engineering science and mechanics. Saptarshi and colleagues found that if you add just the right amount of background noise, it can actually increase the signal for the sensor.
“For example, a paddlefish that lives in muddy waters cannot actually find its food, which is a phytoplankton called Daphnia, by sight. The paddlefish has electroreceptors that can pick up very weak electric signals from the Daphnia at up to 50 meters. If you add a little bit of noise, it can find the Daphnia at 75 meters or even 100 meters. This ability adds to the evolutionary success of this animal.”
In the study, the team described the process, although the technique has not yet been demonstrated on a silicon photodiode (which would make the device very scalable) — but in theory, any state of the art sensor can be enhanced this way.
The finding could help usher in the so-called Internet of Things (the embedding of internet connection to all sorts of sensors) — sensors have become very cheap and accessible, but there’s still plenty of room for improvement when it comes to weak signals. It’s also oftentimes impractical to add expensive, power-hungry equipment to ensure a low signal. The technique is also applicable in environmental sensors such as monitoring emissions or earthquakes.
Journal Reference: Akhil Dodda et al, Stochastic resonance in MoS2 photodetector, Nature Communications (2020). DOI: 10.1038/s41467-020-18195-0