From Event: SPIE Defense + Security, 2017
We present an investigation of the optical property of orbital angular momentum (OAM) for use in the detection of objects obscured by a turbid underwater channel. In our experiment, a target is illuminated by a Gaussian beam. An optical vortex is formed by passing the object-reflected and backscattered light through a diffractive spiral phase plate at the receiver, which allows for the spatial separation of coherent and non-coherent light. This provides a method for discriminating target from environment. Initial laboratory results show that the ballistic target return can be detected 2-3 orders of magnitude below the backscatter clutter level. Furthermore, the detection of this coherent component is accomplished with the use of a complicated optical heterodyning scheme. The results suggest new optical sensing techniques for underwater imaging or LIDAR.
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Brandon Cochenour, Lila Rodgers, Alan Laux, Linda Mullen, Kaitlyn Morgan, Jerome K. Miller, and Eric G. Johnson, "The detection of objects in a turbid underwater medium using orbital angular momentum (OAM)," Proc. SPIE 10186, Ocean Sensing and Monitoring IX, 1018603 (Presented at SPIE Defense + Security: April 11, 2017; Published: 22 May 2017); https://doi.org/10.1117/12.2264626.