The longitudinal component of a focused beam is split into two parts along the optical axis to obtain a longitudinally polarized long focal depth using amplitude filtering based on Euler transformation and a radially polarized Bessel-Gaussian beam. Numerical results indicate that long focal depth and FWHM can be easily achieved with 9lambda and 0.8lambda, respectively. A radially polarized beam can be converted into a longitudinally polarized beam with a conversion efficiency of 51.0percent. It can therefore be believed that the proposed scheme can be widely used to generate a long-itudinally polarized beam for particle acceleration, laser cutting, and optical trapping.
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