How can one take a photo of photons in motion at a trillion frames per second?
We use a pico-second accurate detector. We use a special imager called a streak tube that behaves like an oscilloscope with corresponding trigger and deflection of beams. A light pulse enters the instrument through a narrow slit along one direction. It is then deflected in the perpendicular direction so that photons that arrive first hit the detector at a different position compared to photons that arrive later. The resulting image forms a "streak" of light. Streak tubes are often used in chemistry or biology to observe milimeter sized objects but rarely for free space imaging.
