Scientists have developed an N-slit laser interferometer that is suitable for secure terrestrial free-space optical communications over propagation distances and clear-air turbulence detection.

The device was created by physicists from Interferometric Optics and the US Army Space and Missile Defense Command. The findings were reported in the Feb. 3, 2011, issue of Journal of Optics (doi: 10.1088/2040-8978/13/3/035710).

Previously, N-slit interferometers were used for industrial metrology applications, including microdensitometry, microscopy and optical modulation measurement of thin-film gratings generated from a variety of manufacturing processes. Advantages of this type of interferometer include a simple architecture and the use of low- to medium-power single-transverse-mode narrow-linewidth lasers.

The scientists proved experimentally that the device is a viable interferometric tool over long free-space propagation paths under fair atmospheric conditions. In the lab, they demonstrated that very subtle attempts to intercept the interferometric characters, using microscopic natural fibers, could be detected by observing the diffraction patterns superimposed over the interferometric signal.

The US Army High Energy Laser Laboratory project was funded through a subcontract to BAE Systems.