Understanding Structured Terahertz Beams Containing Orbital Angular Momentum for Agile Aerial Sensing
Abstract
Electromagnetic waves can contain orbital angular momentum(OAM). This unique wave structure has a spatial phase front that twists in a helical fashion as it propagates. Interestingly, different rates of phase rotations form a set of orthogonal modes. OAM beams have been mostly investigated in the optical regime to scale the communication capacity via mode multiplexing in stationary settings. In principle, Terahertz waves can also contain OAM beams, yet, this scope has remained relatively unexplored. Combining the unique propagation characteristics of the terahertz waves with the inherent structural properties of OAM beams has the potential to dramatically impact multiple DoD disciplines. However, it has a rich set of basic research challenges. This project lays the foundation for understanding and exploiting OAM terahertz beams for agile airborne sensing. Our scientific study includes fundamental modeling, numerical analysis, and experimental investigation. First, the higher Terahertz beam divergence imposes strict requirements on the receiver size and the operating distance. We will study the theoretical bounds to preserve a certain level of mode orthogonality .Further, the mobility-induced drifts and misalignments cause phase distortion and modal coupling. We will investigate the complex OAM spectrum across diverse frequencies to extract the location and orientation of the receiver. Second, as OAM beams pass through a turbulent medium, the temporal-spatial fluctuations in phase would leave unique signatures in the complex OAM profile. We will study the interaction of turbulence with OAM-carrying Terahertz beams with the goal of making a breakthrough in the science of turbulence by extracting and quantifying turbulence s statistical variables from the spectral-modal signatures. Finally, we will design and prototype meta surfaces to generate pure terahertz OAM modes at wide bandwidth and under strict SWAP-C constraints. This project, if successful, will transform the physic of sensing by integrating the inherent characteristics of terahertz frequencies and OAM-structured wavefronts.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Feb 06, 2025
- Source ID
- FA95502410144
Entities
People
- Yasaman Ghasempour
Organizations
- Air Force Office of Scientific Research
- Trustees of Princeton University
- United States Air Force