Grant: Discovery Grants Program - Individual

The precision and power of a laser beam is so well understood that it has entered the popular lexicon ("laser-like focus"), but there is another parameter of light that has emerged as the linchpin to the most demanding applications: phase. Phase is the common element enabling innovations ranging from the latest generation of optical telecommunications to gravitational wave detectors. Phase can be thought of as the position of the crest of the light wave relative to another light wave. When a second beam is added "in-phase", crests line up and the total intensity quadruples. But if that second beam is shifted by a minute amount (submicron for visible light) so the two waves end up in opposite phase, they will cancel making the total intensity zero. We will harness the wonderful sensitivity provided by optical phase to build detectors to see things that have never been seen before. DG funding will allow us to: Theme 1: Monitor and control laser-based manufacturing to improve sustainability Manufacturers are retooling production lines to use intense lasers to cut, weld and even build sophisticated 3D structures out of lightweight advanced metal alloys, but the microscale environment at the focus of a kW beam and metal is extreme and can be erratic. Defects hidden within a part can lead to loss of life and recalls costing billions. We exploited phase to open a new window into high-power laser processing and used it to solve some key challenges in advanced manufacturing (commercialized by successful spin-off Laser Depth Dynamics). Even with such advances, a mystery remains: during laser processing, our phase-sensitive imaging system often loses the metal workpiece - it just disappears. Preliminary results suggest high-speed instabilities (linked to defect formation) are the main culprit. We will implement a stroboscopic phase-sensitive imaging system to "freeze" motion on the fastest time scales. This approach will allow us to unravel not only the mystery of disappearing interfaces, but also to deepen our understanding of the light-matter process itself, with potential benefits to laser welding (critical to electric vehicle manufacturing) and 3D metal additive manufacturing. Theme 2: Searching for the dark photon Two of the most profound questions of our time are: What is dark matter? Does it interact through unknown forces? The "dark photon" could answer both questions. We aim to catch a glimmer of this force carrier by building a supremely sensitive detector. We will transfer the optical phase of two counterpropagating light beams onto 10^19 molecules. Now working as one, the most minute perturbation will trigger the ensemble to emit a burst of light. Even if dark photons do not exist, our system is a promising platform for amplification of minute signals for a variety of applications including remote pollutant identification and single-molecule sensing.