University of Delaware - College of Engineering
ELECTRICAL & COMPUTER ENGINEERING

Research

Photonics & Electromagnetics

Micromechanical Large-Area Modulators for Free-space Optical Communication

Keith Goossen

Free space optical links in which one of the nodes is not a light source, but rather, reflects a modulated beam, have great advantages in several situations. In the first, pictured below, one of the nodes has low energy reserves, in this case since it is a lightweight Unmanned Aerial Vehicle (UAV), and so it is favorable to have an energy efficient reflective light modulator, rather than an on-board laser, to perform communication. These optical links also have an important advantage in that since the optical beam is retro-reflected, it returns directly to the source with little spreading, and thus is highly secure. We have constructed modulators based upon silicon Microelectromechanical fabrication technology. The modulator can basically be thought of as a variable reflectance mirror, thus converting an on-board electrical signal, which could for example be the video feed from the on-board camera, into a modulated return beam. Other situations in which such devices are useful are as secure tags for soldiers and equipment in the field. For example, soldier mounted tags could have a daily programmed digital modulation signal, so that in firefights a "friend" return signal is returned to weaponry with mounted laser interrogators. By using mass-producible silicon microelectronics technology for these modulators, they can cheaply be distributed throughout the military.

Recent publications

K.W. Goossen, "Micromechanical Etalon Modulator Designs with Wide Angular Tolerance for Free Space Optical Links," IEEE Photon. Tech. Lett., vol. 18, pp. 959-961 (2006).


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