Terahertz vortex beam generator based on a photopatterned large birefringence liquid crystal. 
A terahertz (THz) q-plate is proposed and demonstrated to generate THz vortex beams.  It is composed of a large birefringence liquid crystal (LC) with spatially-varying director distribution sandwiched by two pieces of fused silica glass.  A polarization-sensitive alignment agent is photopatterned to carry out the specific LC director distribution.  THz vortex beams with different topological charges are characterized with a THz digital holographic imaging system.  The intensity and phase distributions consistent with theoretical analyses are obtained.  Besides, an eight-lobed intensity distribution is observed corresponding to the vertical polarization component of a cylindrical vector beam.  This work may inspire novel THz applications.