Generation of limited-diffractive twisted pulses

In this work, we investigate the possibility to generate a limited-diffractive electromagnetic twisted pulse carrying an orbital angular momentum (OAM). To this aim, a higher-order Bessel beam with an azimuthal phase variation is generated by enforcing an inward cylindrical travelling wave aperture distribution over a finite aperture. The normal component of the electric field is first computed within the Fresnel region, at a single frequency in the microwave range. Then, the electric field is evaluated for different frequencies over a limited fractional bandwidth centered around the carrier frequency. Finally, the time-domain description of the electric field is obtained by means of an inverse Fourier transform of the previously generated electric fields. Numerical results demonstrate the peculiar twisted shape of a pulse with limited spatio-temporal broadening over the propagating axis.