A pseudo non-diffracting microwave vortex

Abstract

Recent computations, performed with the well-known Mathematica program, have produced rigorous, closed-form, symbolic expressions of the cylindrical E-field, and Hfield components of a planar, circular-aperture field-distribution that appears to generate a radiation-pattern exhibiting the propagation-invariance of the so-called "pseudo nondiffracting" optical Bessel-beams. The new planar, circular-aperture field-distribution obtained includes radial-, azimuth-, and axial-components of both the E-field, and Hfield with different linearly-dependent azimuth phases. Further, only the axial-( * z S ), and azimuth-( ϕ * S ) components of the complex Poynting Vector are non-zero, while the radial component * r S is identically-zero, everywhere on and above the aperture-plane, at all radial distances from the broadside-axis, and at all axial-distances from the apertureplane. The generated wave-front has the shape of a 3D helicoid-surface, with a pitch being a function of the z r k k ratio. The diffraction-properties of the generated radiationpattern are being computed by using the "Direct Electromagnetic Field Integration" method, reported by Walter Franz in 1948 [2], and reviewed by Chen-To Tai in 2000 [3].

More unusual features of the microwave vortex

“…In shifting from light to radio wavelengths, it is necessary to shift focus away from momentum to classical electric and magnetic field descriptions of waves and their phase and velocity behaviors rather than momentum and force. R.A. Speciale [1]- [2] examined a field solution that was a superposition of TE and TM Bessel modes, but did not obtain a complete modal description, which is supplied here.…”