N-slit interferometer for secure free-space optical communications: 527 m intrainterferometric path length

Abstract

The N-slit interferometer is demonstrated to function with an intra interferometric propagation pathlength of 527.33 m. Interferograms representing several interferometric characters, corresponding toN = 2, 3, 4, and 5, were recorded at the interferometric plane located at the end of an open airpropagation range. Interferometric computations, based on the application ofDirac’s notation, were successfully used to predict the structure and divergence ofthe propagating interferograms. These measurements were carried out during anunusual mild-temperature, low-humidity, summer night in northern Alabama. In thelaboratory, at an intra interferometric propagation path length of 7.235 m, theN-slit interferometer was also used to successfully detect the intrusion of microscopicfibers into the intra interferometric propagation path. These experiments ledto the detection of diffraction patterns superimposed over the interferograms.