 devices to be produced on a single chip, each with its own designed emission properties." Such lasers-on-chips may lead to new possibilities for optical communica- tions, as well as other optoelectronic and sensing technologies. QC lasers have already been used to make extremely sensitive sensors, including sensors that have been used by NASA for atmospheric monitoring. "The next step is to see if we can use this sort of technique to get sensing done within the laser," says Federico Capasso, a Harvard University consult- ant who is also a Bell Labs consultant and one of the inventors of the QC laser. "If we can fill the holes of the photonic crystal in this laser with nano- liters of fluid or other special material, we may get some interesting physics as well as a whole new world of applications." 4.6.6 Looking Into Lasers University of Toronto researchers are looking to create more powerful and efficient lasers for fiber-optic communication systems by looking inside lasers while they are operating. "We've seen the inner workings of a laser in action," says investigator Ted Sargent, a professor in the university's department of electrical and computer engineering. "We've produced a topographical map of the landscape that electrons see as they flow into these lasers to produce light." He says the findings could influence laser design, change the diagnosis of faulty lasers, and potentially reduce manufacturing costs. Lasers are created by growing a complex and carefully designed series of nanometer-sized layers of crystals on a disk of semiconductor material known as a wafer. Ridges are etched into the crystal surface to guide laser light, thin metal layers are added on top and bottom, and the wafer is then cut into tiny cubes or chips. During the laser's operation, an electrical current flows into the chip, providing the energy to generate intense light at a specific wavelength used in fiber-optic communications. The University of Toronto researchers focused their efforts on the "beating heart" portion of the las