Researchers at Princeton University developed a technique for generating a laser beam out of nothing but air. They focus a pump laser on a distant point in the air and another laser beam comes back. The video shows 100 pulses of infra-red light from this “air laser.” The center region represents the highest intensity; the outer areas have lower intensity light. The technique could be used for sensing minute quantities of gas in the air from a distance.
Credit: Image courtesy Arthur Dogariu, Princeton University