14 DAY TRIAL // Controlling the polarization of lasers, as in the orientation of the wave oscillation, has been a long-term objective for physicists, on account of the fact that figuring out how to do this could open new avenues of research, especially in the fields of photonics and communication. Now, an international team comprised of experts from the Harvard School of Engineering and Applied Sciences (SEAS) and the Hamamatsu Photonics, in Hamamatsu City, Japan, have managed to do just that, when they have created lasers whose polarization could be designed and controlled at will.
“Polarization is one of the key features defining a laser beam. Controlling it represents an important new step towards beam engineering of lasers with unprecedented flexibility, tailored for specific applications,” the SEAS Vinton Hayes Senior Research Fellow in Electrical Engineering Federico Capasso, who is also the Robert L. Wallace Professor of Applied Physics, explains. He has spearheaded the investigation for Harvard, along with graduate student Nanfang Yu.
“The novelty of our approach is that instead of being conducted externally, which requires bulky and expensive optical components, manipulation of the beam polarization is achieved by directly integrating the polarizer on the laser facet. This compact solution is applicable to semiconductor lasers and other solid-state lasers, all the way from communication wavelengths to the mid-infrared and Terahertz spectrum,” he adds. A paper detailing the finds will be published today, in the April 13th issue of the scientific journal Applied Physics Letters, as a cover story.
One immediately possible application for the innovation would be better satellite control, as modern communication devices rely on two beams of lasers to guide them through the skies. However, the experts say that using two orthogonal polarizations in these lasers could double the capacity of the channels, and therefore increase the amounts of traffic circulating through them. In addition, various states of polarization could be of some assistance in quantum cryptography, experts maintain.
The Nanoscale Science and Engineering Center (NSEC), which is funded by the National Science Foundation (NSF), and the Center for Nanoscale Systems (CNS), both based at Harvard, have contributed to the research as well. The new study was partially funded by the Air Force Office of Scientific Research and also co-authored by Harvard's postdoctoral researcher Qijie Wang and research associates Christian Pflügl and Laurent Diehl, as well as by Hamamatsu Photonics' researchers Tadataka Edamura, Sninichi Furuta, and Masamichi Yamanishi.