- The temperature of an object increases when a beam of enough energy is illuminated on it.
- The thermal radiation emitted by this object could be used for super-resolution imaging at every scale.
Think of three scenarios: a bat navigates its way to prey in the night; you look for your lost items with a flashlight; a car’s radar locates other nearby vehicles. What’s common in all of them?
The same physical principle is applied in all cases. Be it sound, light, or an electromagnetic wave, a beam goes ahead, and the same type of reflected wave brings the relevant data back to the sender.
The phenomenon also describes how stealth aircraft escape radars: they become invisible because they absorb radar energy, and reflect a very low-energy (undetectable) signal. Usually, this absorbed energy is transformed into heat, which increases the object’s temperature.
But what if you could use this heat energy to do something ‘useful’? Now, researchers at the Institute for Basic Science in South Korea, have discovered that the temperature elevation due to a probe beam can be used to produce signals for identifying objects.
Unlike traditional methods whose applications are limited to microcopy only, this new technique, called ‘active thermal detection’, enables super-resolution imaging at every scale, unveiling tiny image details.
Detect Objects Through Their Thermal Radiation
The temperature of the object increases when a probe beam of enough energy is illuminated on the object. The more the temperature, the more it will emit thermal radiation.
In other words, if a focused beam of energy is illuminated on an object that absorbs and linearly transforms the energy into heat, a highly nonlinear thermal radiation response is produced.
Reference: Nature Communications | DOI:10.1038/s41467-019-13780-4 | IBS
In this study, researchers were able to verify the thermal radiation’s super-linearity. They calculated how many photons a heated object emits and demonstrated that even a minor variation in temperature could substantially change the emission of photons.
Putting these two processes together (active heating and detection phase), they were able to detect objects at very high resolutions. And with a sufficiently high temperature, the resolution factor can be arbitrarily cranked up.
Applications
The findings show that active thermal detection could be used for detecting stealth objects, and testing radar and Lidar technology for autonomous vehicles.
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It opens new avenues for recently developed thermal photodetectors, such as mercury cadmium telluride avalanche photodiodes. The study also encourages the development of a new class of thermal probes for imaging at all spatial scales, with a much broader diversity of objects.
