Beam mid-infrared light waves across a power plant’s smokestack and you can measure the flow of gaseous pollutants. Feed that data back to the plant and you can trim pollution and fuel consumption. It’s just one opportunity created by the quantum cascade laser. The laser, invented at Bell Labs in 1994, had promise as the heart of a smaller, less expensive, more efficient apparatus for monitoring smokestack emissions. But when Austrian physicist Claire Gmachl arrived at Bell Labs in 1996,the laser still had one fatal flaw: a messy, broad-spectrum beam. Within a year, Gmachl had the problem licked. She amplified one portion of the beam by sculpting the laser crystal into an echo chamber for photons. It was a major leap, and colleagues say the intense Gmachl has since delivered an average of two advances of similar importance each year. She’s also been experimenting with lasers tuned to identify telltale gases found in our breath that may indicate everything from asthma to heart disease. Now Gmachl is focused on carrying data in fiber optics, where rapid-pulse lasers could help sate our hunger for bandwidth.