er (called the active region), where electronic energy is converted into light. Using a technique called scanning voltage microscopy, they examined the surface of an operating laser, picking up differences in voltage. These differences translate to a topographical image of the laser's energy surface, allowing researchers to visualize the forces an electron expe- riences along its path into the active region, Sargent says. THE FUTURE IS FIBER-OPTICAL TECHNOLOGIES The team used its newly acquired information about the inside operations of the laser to determine the fraction of electric current that contributes to producing light. The balance of electrons are undesirably diverted from the active region: such current leakage wastes electrons and heats the device up, degrading performance. "We used direct imaging to resolve a contentious issue in the field: the effectiveness of electronic funneling into the active region of a ridge-waveguide laser," says Dayan Ban, a University of Toronto doctoral candidate who made the measurements. "Previously, uncorroborated models had fueled speculation by yielding divergent results. Now we know where the electrons go." Ban is now a researcher at the Institute for Microstructural Sciences of the National Research Council of Canada. "Direct imaging of the functions that drive the action of a living laser could transform how we think about laser 'diagnosis and therapy,'" says Sargent, referring to the measurement and optimization of laser structures and their determination of the devices' inner workings. Designers now use a variety of computer simulations to model how lasers work, but research at the Univer- sity of Toronto may show which simulations are the most accurate design tools. "With accurate models," says Sargent, "the designs we can create are more likely to result in devices that meet design requirements." The research could also help in diagnosing faulty lasers. "If a particular laser fails, the kind of measurements that we are taking could provide some idea of why it fa