Design and light field analysis of biconical axicon for generating terahertz Bessel beam

A biconical axicon structure that can generate terahertz Bessel beams with long non-diffraction distance is designed. The optical element is centered on the axis of the traditional axicon and grinds the bottom surface of the axicon into a conical surface. The non-diffraction distance and light field distribution expression of terahertz Bessel beam generated by biconical axicon are theoretically analyzed. The light field distribution characteristics of traditional axicon and biconical axicon are numerically simulated. The results show that the terahertz wave can generate a terahertz Bessel beam with a non-diffraction distance of 110.18 mm through a biconical axicon with a bottom angle of 20 ° and 15 °. Under the same parameters, the traditional axicon can only generate a terahertz Bessel beam of 27.55 mm, and the non-diffraction distance is broadened by 82.63 mm.