Molecular device turns infrared into visible light

Our eyes can detect frequencies between 400-750 THz, which define the visible spectrum.

At lower frequencies, the energy transported by light isn't enough to trigger photoreceptors in our eyes and in many other sensors, which is a problem given that there is rich information available at frequencies below 100 THz, the mid- and far-infrared spectrum.

For example, a body with surface temperature of 20°C emits infrared light up to 10 THz, which can be "seen" with thermal imaging, meaning that we can identify them remotely and non-destructively by infrared spectroscopy, which has myriads of applications.

Scientists have now developed a new way to detect infrared light by changing its frequency to that of visible light.

The researchers adding energy to infrared light with a mediator: tiny vibrating molecules. The infrared light is directed to the molecules where it is converted into vibrational energy.

A laser beam of higher frequency impinges on the same molecules to provide the extra energy and convert the vibration into visible light. To boost the conversion process, the molecules are sandwiched between metallic nanostructures that act as optical antennas by concentrating the infrared light and laser energy at the molecules.

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. Second, each device is about a few micrometres in length and width, which means it can be incorporated into large pixel arrays.