Figure 2
From: Demonstration of a terahertz pure vector beam by tailoring geometric phase
Phase retardance by refractive indices. (a) Relationship between slope angle of non-axially-symmetric half-wave plate and phase retardance. An incident linearly polarized beam generates phase retardance after reflection within a Fresnel rhomb with refractive index n and slope angle β. Phase retardance is related to the slope angles and refractive indices n = 1.52 (solid, blue) of high-density polyethylene (HDPE) and n = 1.44 (dashed, red) polytetrafluoroethylene (PTFE). (b) Frequency dependences of phase retardance are described with n = 1.52 (solid, blue) and n = 1.44 (dashed, red), respectively. HDPE and PTFE enable the use of THz frequency regions. The slope angles of HDPE and PTFE are set to 55° due to the non-axially-symmetric half-wave plate and the axially-symmetric wave plate, respectively.
