Conversion of infrared to visible light possible with new breakthrough

In a new study published in Science, researchers have developed a new method for detecting infrared light by changing its frequency to a corresponding frequency in the range of visible light.

Electromagnetic waves have a characteristic frequency and wavelength that are inversely proportional; as one increases, the other decreases. Measured in Hertz (Hz), human eyes can perceive light frequencies between 400 and 750 trillion Hz, or terahertz (THz). Smartphone cameras can detect down to 300 THz, and other detectors used in fiber-optic cables can detect around 200 THz.

Lower frequency light does not have sufficient energy to be registered by the photoreceptors in our eyes, meaning we cannot see frequencies of light like infrared that fall below this threshold but contain a great deal of information. As everything with warmth radiates energy, temperature differences can be detected visually with infrared spectroscopy, remotely, and without contact.

Scientists from the Swiss Federal Institute of Technology Lausanne (EPFL), the Wuhan Institute of Technology, the Valencia Polytechnic University, and the Netherlands' AMOLF have now developed a device that can convert the frequencies it detects in the infrared portion of the electromagnetic spectrum to those in visible light. Tiny molecules built into the device are hit with incoming infrared light, which is converted into vibrational energy as the molecules begin to vibrate. The molecules are then hit with a higher frequency laser to provide additional energy to convert the vibration into visible light.

"The new device has a number of appealing features. First, the conversion process is coherent, meaning that all information present in the original infrared light is faithfully mapped onto the newly created visible light. It allows high-resolution infrared spectroscopy to be performed with standard detectors like those found in cell-phone cameras. Second, each device is about a few micrometers in length and width, which means it can be incorporated into large pixel arrays. Finally, the method is highly versatile and can be adapted to different frequencies by simply choosing molecules with different vibrational modes," says Professor Christophe Galland at EPFL's School of Basic Sciences, who led the study."

Dr. Wen, the first author of the study, notes the very low efficiency of the light conversion in the device, which they are working to improve to increase its viability in commercial applications.

You can read more from the study here.