Published in the Feb. 24th issue of Nature, the proof of concept model was developed by Mariano Troccoli, Ertugrul Cubukcu and Federico Capasso of the Harvard University Division of Engineering and Applied Sciences; Alexey Belyanin of Texas A&M University; and Deborah L. Sivco and Alfred Y. Cho of Bell Laboratories, Lucent Technologies. The finding was supported in part by Texas A&M's Telecommunications and Informatics Task Force Initiative.
Conventional Raman lasers depend on a fundamental phenomenon in physics called the Raman effect-the change in the frequency of monochromatic light (such as a laser) when it passes through a substance. When light from an intense exciting laser beam, known as the "pump," deflects off the molecules of certain materials, some of the incident photons lose part of their energy. As a result, a secondary laser beam with a frequency shifted from that of the exciting laser emerges from the material.
"Raman lasers have been used for a long time," Troccoli says. "In general they require a large and powerful external pump to compensate for the beam's attenuation, or weakening, as it propagates through the material. In our work, we were able to put the pump and the material itself into a single device."
The team's ability to combine the power source and the Raman material together, literally creating a laser-within-a-laser, has resulted in several key innovations. The injection laser is the first current-driven Raman laser; in essence, it can be plugged in.