THz Multi‐Mode Q‐Plate with a Fixed Rate of Change of the Optical Axis Using Form Birefringence

Abstract

We report the design, fabrication and experimental validation of a THz all‐dielectric multi-mode q‐plate having a fixed rate of change of the optical axis. The device consists of space‐variant birefringent slabs manufactured by 3D printing using melt‐extruded Acrylonitrile Butadiene Sty-rene (ABS). The desired form birefringence is analytically evaluated and experimentally measured by the THz time domain spectroscopy technique. The manufactured q‐plate design is characterized using a polarization‐sensitive imaging setup. The full electric field spatial maps are acquired from the beam propagating through the q‐plate. The device enables the realization of both radial and azimuthal vector beams at discrete frequency intervals by controlling the space‐dependent orienta-tion of the ordinary and extraordinary axes in the transverse plane with a multi‐mode sequence.