AUTHOR=Wang Miao , Wang Xinke , Han Peng , Sun Wenfeng , Feng Shengfei , Ye Jiasheng , Zhang Yan 

TITLE=Longitudinal Component Properties of Circularly Polarized Terahertz Vortex Beams

JOURNAL=Frontiers in Physics

VOLUME=9

YEAR=2021

URL=https://www.frontiersin.org/journals/physics/articles/10.3389/fphy.2021.736831

DOI=10.3389/fphy.2021.736831

ISSN=2296-424X

ABSTRACT=<p>A circularly polarized vortex beam possesses similar focusing properties as a radially polarized beam. This type of beam is highly valuable for developing optical manufacturing technology, microscopy, and particle manipulation. In this work, a left-hand circularly polarized terahertz (THz) vortex beam (CPTVB) is generated by utilizing a THz quarter wave plate and a spiral phase plate. Focusing properties of its longitudinal component <italic>E</italic><sub><italic>z</italic></sub> are detailedly discussed on the simulation and experiment. With reducing the F-number of the THz beam and comparing with a transverse component <italic>E</italic><sub><italic>x</italic></sub> of a general circularly polarized THz beam, the simulation results show that the focal spot size and intensity of its <italic>E</italic><sub><italic>z</italic></sub> component can reach 87 and 50% of <italic>E</italic><sub><italic>x</italic></sub> under a same focusing condition. In addition, the experimental results still demonstrate that the left-hand CPTVB can always maintain fine <italic>E</italic><sub><italic>z</italic></sub> focusing properties in a broad bandwidth, which manifest the feasibility of this class of THz beams.</p>