Creation of Optical Tubes with Tunable Inner Diameters

Based on the radiation pattern of a magneto-electric antenna, which combines a magnetic dipole and an electric dipole, we propose a method for generating an optical tube with a tunable inner diameter in a 4π system. Numerical results indicate that the inner diameter of the optical tube produced by this method is adjustable, with the Full Width at Half Maximum (FWHM) of the inner diameter ranging from approximately 0.30λ to nearly zero, overcoming the limitation of fixed inner diameters in conventional optical tubes. This novel tunable inner diameter optical tube holds significant application value in the fields of laser guiding tubes and optical micromanipulation.