Author,Title,Journal,ISSN,Publisher,Date,Volume,Number,Page,URL,URL(DOI) K. Miyamoto and K. Suizu and T. Akiba and T. Omatsu,Direct observation of the topological charge of a terahertz vortex beam generated by a Tsurupica spiral phase plate,Applied Physics Letters,0003-6951,AIP Publishing,2014-06-30,104,26,261104,https://cir.nii.ac.jp/crid/1360283692078756736,https://doi.org/10.1063/1.4886407