Our group, in collaboration with Wuhan Institute of Technology, the Valencia Polytechnic University, and AMOLF in the Netherlands, has now developed a new way to detect infrared light by changing its frequency to that of visible light. The device can extend the “sight” of commonly available and highly sensitive detectors for visible light far into the infrared. The breakthrough is published in Science.
Frequency conversion is not an easy task. The frequency of light is a fundamental that cannot easily change by reflecting light on a surface or passing it through a material because of the law of energy conservation.
The researchers worked around this by 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. Simultaneously, 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.