Beams of light, indeed all electromagnetic waves, can carry orbital angular momentum (OAM). An OAM beam is uniquely structured, such that the spatial phase front “twists” in a helical fashion as it propagates, and different rates of phase change form a set of orthogonal modes.
Utilizing multiple EM waves with different OAM values has been relatively unexplored, with a rich set of basic research challenges that has the potential to dramatically impact multiple DoD disciplines. Each different OAM beam has a uniquely structured phase front and a central intensity null that are sensitive to disruption by interacting with each other and with matter. We will explore using multiple OAM beams: (i) simultaneously for capacity/local power gain from multiplexing, or (ii) sequentially for diversity gain using multiple unique measurements. If successful, new knowledge and >10X performance enhancements will be achieved.
Our curiosity-driven and focused scientific study includes: (i) mechanisms for minimizing and maximizing the linear and nonlinear interactions among beams and with different types of matter (air, objects, sub-wavelength structures); and (ii) dependencies of OAM modal structures under harsh conditions. We will investigate: (a) the complex OAM spectrum; (b) interaction of structured beams with matter; (c) temporal/spatial characterization in nonlinear media, and (d) extraction/quantification of OAM signatures produced during interaction. We will explore tailoring of the beams’ structure and methods for signature analysis/recovery.
We will examine proof-of-concept capabilities, including: (a) Communications: Capacity can be multiplied by simultaneously transmitting multiple beams, and the beams’ can be tailored to limit eavesdropping. (b) Imaging: multiple structured beams can improve measurement sensitivity to sub-diffraction-limited resolution, and (c) Directed energy: different modes can be combined coherently to form spatial patterns with localized >10X intensity gain