Researchers in Australia have developed a new way to send digital information that is almost impossible to detect.
The technique uses a phenomenon called “negative luminescence” to hide data signals inside natural heat radiation, making it appear as though no communication is happening at all.
The technology was developed by engineers from UNSW Sydney and Monash University.
Their work, published in Light: Science & Applications, could eventually provide a powerful new layer of security for sensitive communications in fields such as defense, finance, and cybersecurity.
In traditional communication systems, data is transmitted using signals that can be detected, even if the information itself is encrypted.
For example, radio waves, flashing lights, or signals traveling through fiber-optic cables clearly show that data is being sent.
While encryption protects the message, outsiders can still see that communication is happening.
The new system takes a different approach. Instead of simply encrypting information, it hides the very presence of the signal.
The method works by using special electronic devices called thermoradiative diodes. These devices produce tiny changes in infrared radiation, the heat energy naturally emitted by all objects. Normally this heat radiation forms a background glow that is invisible to the human eye but can be detected by thermal cameras.
Negative luminescence allows the device to create signals that appear darker than the surrounding background heat radiation.
In simple terms, it is similar to a flashlight that could somehow become darker than being turned off. While that might sound impossible with normal light, certain materials can create this effect in the infrared part of the spectrum.
By rapidly switching between slightly brighter and slightly darker infrared signals, the device can encode digital information. Because these signals blend perfectly into the natural background radiation, outside observers cannot easily detect that data is being transmitted.
Only receivers equipped with specialized sensors and knowledge of the signal pattern can detect and decode the hidden message.
Dr. Michael Nielsen from UNSW, the lead author of the study, said the idea could significantly improve data security. If potential attackers cannot even see that a communication channel exists, it becomes far harder for them to intercept or hack the data.
Early laboratory experiments have already demonstrated data transfer speeds of around 100 kilobytes per second. While this is relatively slow compared with modern internet speeds, researchers believe the technology could become much faster with improved materials and hardware.
Future versions of the system could potentially reach gigabyte-per-second data rates, especially if advanced materials such as graphene are used to build the devices.
The idea for the technology emerged from earlier research on “night-time solar power,” where thermoradiative devices were used to generate electricity after sunset by releasing heat into the night sky.
Now the same underlying physics is being explored for secure communications. The research team has already demonstrated that their system can send signals in all directions, and they hope future versions will be able to transmit data in targeted beams or even through guided communication channels similar to fiber-optic cables.
If further development succeeds, “negative light” communication could offer a new way to protect sensitive data by making transmissions effectively invisible to the outside world.
