The researchers have developed the world’s first “photon microscope” which can observe clear color images using a superconducting photosensor, even with extremely weak light that cannot be observed with conventional optical microscopes.

Outline of the developed photon microscope and example of measurement

The researchers have developed a photon microscope using a superconducting photosensor as a photodetector. Extremely weak light from a measuring point of a sample is collected, and directed to the sensor in a refrigerator (temperature: 100 mK) using an optical fiber. Each photon is detected and its wavelength is measured with the superconducting photosensor. The color of the measuring point is identified from the number of photons and their wavelengths detected in a fixed time. The sample is scanned to obtain a color image. In the example shown above, the average number of photons at one measurement point is about 20 (exposure time: 50 ms).

Although optical microscopes are often used for color image observation, the image becomes dark and unclear if the light is extremely weak. AIST has developed light detection technology using superconductivity for highly precise detection of photons. When a photon enters the superconducting photosensor developed by AIST, its energy temporarily breaks the superconducting state of the photosensor and its electric resistance changes, so the photon energy is determined. The wavelength of the photon can also be identified from the magnitude of the resistance change.

AIST will demonstrate the effectiveness of the photon microscope in the field of drug discovery and therapeutics by spectrally observing weak luminescence from living cells that could not be observed until now. AIST will also work to develop a technology for color video shooting by increasing the number of sensing elements.