Results for “Laguerre-Gaussian Beams”

NASA NTRSDate not supplied

Sidelobe Reduction and Mode-Purity Enhancement of Vortex Beams from a Programmable, Rectangular Phased Array Antenna

Tapering the magnitude of the electric field excitation of a programmable, rectangular phased array has been employed to achieve sidelobe reduction and enhancement of mode purity in vortex beams, which carry non-zero orbital angular momentum. Far-field radiation patterns pertaining to a commercial-off-the-shelf, 256-element antenna were generated via electromagnetic simulation. The patterns were decomposed into weighted sums of Laguerre-Gaussian modes. The extracted coupling coefficients were used to gauge mode purity. In comparison to a uniform excitation of the phased array elements, our studies indicate that employing a tapering technique can result in a 10.7 dB reduction of sidelobe power and a 7.22 dB improvement in worst-case, mode-to-mode cross-talk.

orbital angular momentum, phased array, beamformin↗

NASA NTRSDate not supplied

Vortex Beam Sidelobe Suppression via Bayliss Synthesis from a Rectangular Phased Array

We demonstrate the application of the Bayliss synthesis method for suppression of sidelobes in an OAM vortex beam, when generated by a commercial-of-the-shelf, rectangular phased array. The method is optimized for the current application and simulated for a 26.5 GHz signal in CST Microwave Studio. Sidelobes are notably reduced by 16.9 dB, with minimal reduction in gain and increase in beamwidth, as compared to a uniformed stimulated phased array. Further, the OAM modes are found to have greater purity that that of the uniformly stimulated array, as well as for other amplitude tapering methods. The Bayliss synthesis is then applied to a phased array in a test range, verifying the simulation results that demonstrate sidelobe suppression. These results indicate that OAM may be applied to existing phased arrays with minimal effort.

Orbital Angular Momentum (OAM)↗

NASA NTRSDate not supplied

Vortex Beam Sidelobe Suppression via Bayliss Synthesis from a Rectangular Phased Array

We demonstrate the application of the Bayliss synthesis method for suppression of sidelobes in an OAM vortex beam, when generated by a commercial-of-the-shelf, rectangular phased array. The method is optimized for the current application and simulated for a 26.5 GHz signal in CST Microwave Studio. Sidelobes are notably reduced by 16.9 dB, with minimal reduction in gain and increase in beamwidth, as compared to a uniformed stimulated phased array. Further, the OAM modes are found to have greater purity that that of the uniformly stimulated array, as well as for other amplitude tapering methods. The Bayliss synthesis is then applied to a phased array in a test range, verifying the simulation results that demonstrate sidelobe suppression. These results indicate that OAM may be applied to existing phased arrays with minimal effort.

Orbital Angular Momentum (OAM)↗

NASA NTRS2018

Does Orbital Angular Momentum Have Effect on Laser’s Scattering by Molecular Atmosphere?

Lasers with orbital angular momentum (OAM) have potential applications in communication technology, manipulation of particles, and remote sensing. Because of its unusual light-scattering properties, the OAM laser’s interaction with a molecular atmosphere must be studied to ensure that it is not lossy for communication or remote-sensing applications that involve its transmission through an atmospheric environment. In this study, the finite-difference time-domain (FDTD) method [21] is applied to calculate the light scattering of the purely azimuthal (the radial mode number is assumed to be zero) Laguerre-Gaussian (LG) beams with OAM by very small dielectric particles. Not like Lorentz-Mie solutions, the FDTD method can calculate for particles off the central axis of the LG beam. It is found that when the particles are very small, and the topological charge number of the OAM of a laser is not extremely large, the laser’s OAM has little effect on the scattering phase function. This suggests that Rayleigh theory can be applied directly to calculate the light scattering by atmospheric molecules. The transmission of a laser beam with OAM in a molecular atmosphere is not different from that of a regular Gaussian beam.

Molecular atmosphere↗